44183403

Annals of Applied Biology ISSN 0003-4746

RESEARCH ARTICLE

Silicon-augmented resistance of plants to herbivorous insects:a reviewO.L. Reynolds1, M.G. Keeping2 & J.H. Meyer3

1 EH Graham Centre for Agricultural Innovation (New South Wales Department of Primary Industries and Charles Sturt University), Private Mail Bag,

Wagga Wagga, NSW 2650, Australia

2 South African Sugarcane Research Institute, Mount Edgecombe 4300, South Africa and School of Biological and Conservation Sciences, University

of KwaZulu-Natal, Scottsville 3209, South Africa

3 Agricultural Consultant, 16 Delaware Avenue, Durban North 4051, South Africa

Keywords

insect–plant interactions; trophic interactions;

resistance; induced plant defences;

constitutive defences; biological control.

Correspondence

O.L. Reynolds (nee Kvedaras), EH Graham

Centre for Agricultural Innovation (New South

Wales Department of Primary Industries and

Charles Sturt University), Private Mail Bag

Wagga Wagga, NSW 2650, Australia.

Email: [email protected]

Received: 18 February 2009; revised version

accepted: 6 June 2009.

doi:10.1111/j.1744-7348.2009.00348.x

Abstract

Silicon (Si) is one of the most abundant elements in the earth’s crust,although its essentiality in plant growth is not clearly established. However,the importance of Si as an element that is particularly beneficial for plantsunder a range of abiotic and biotic stresses is now beyond doubt. This paperreviews progress in exploring the benefits at two- and three-trophic levels andthe underlying mechanism of Si in enhancing the resistance of host plants toherbivorous insects. Numerous studies have shown an enhanced resistance ofplants to insect herbivores including folivores, borers, and phloem and xylemfeeders. Silicon may act directly on insect herbivores leading to a reductionin insect performance and plant damage. Various indirect effects may alsobe caused, for example, by delaying herbivore establishment and thus anincreased chance of exposure to natural enemies, adverse weather events orcontrol measures that target exposed insects. A further indirect effect of Si maybe to increase tolerance of plants to abiotic stresses, notably water stress, whichcan in turn lead to a reduction in insect numbers and plant damage. Thereare two mechanisms by which Si is likely to increase resistance to herbivorefeeding. Increased physical resistance (constitutive), based on solid amorphoussilica, has long been considered the major mechanism of Si-mediated defencesof plants, although there is recent evidence for induced physical defence.Physical resistance involves reduced digestibility and/or increased hardness andabrasiveness of plant tissues because of silica deposition, mainly as opalinephytoliths, in various tissues, including epidermal silica cells. Further, thereis now evidence that soluble Si is involved in induced chemical defences toinsect herbivore attack through the enhanced production of defensive enzymesor possibly the enhanced release of plant volatiles. However, only two studieshave tested for the effect of Si on an insect herbivore and third trophic leveleffects on the herbivore’s predators and parasitoids. One study showed noeffect of Si on natural enemies, but the methods used were not favourable forthe detection of semiochemical-mediated effects. Work recently commencedin Australia is methodologically and conceptually more advanced and an effectof Si on the plants’ ability to generate an induced response by acting at thethird trophic level was observed. This paper provides the first overview of Siin insect herbivore resistance studies, and highlights novel, recent hypothesesand findings in this area of research. Finally, we make suggestions for futureresearch efforts in the use of Si to enhance plant resistance to insect herbivores.

Ann Appl Biol 155 (2009) 171–186 © 2009 The Authors 171Journal compilation © 2009 Association of Applied Biologists

Silicon and insect herbivores O.L. Reynolds et al.

Introduction

Silicon (Si) is only second in abundance to oxygen in theearth’s crust, although its essentiality in plant growth isnot clearly established. However, the importance of Sias a nutrient that is particularly beneficial for plantsunder a range of abiotic and biotic stresses, is nowbeyond doubt. Insect herbivores represent one classof biotic stressors that Si can provide some defenceagainst. Silicon is taken up by plants in the form ofmonosilicic acid and is transported from the roots tothe shoots, and when concentrated over a critical level(approximately 100 ppm at biological pH), it polymerisesas opaline phytoliths, which comprise the bulk of aplant’s Si content (Jones & Handreck, 1967). WhetherSi is taken up through the leaves remains controversial(Guevel et al., 2007). Although Si deposition in theepidermal cells of plants is purportedly responsible for theprotective effects of Si against plant diseases and insectherbivores (Ma, 2004), there is increasing evidence forSi-induced chemical defence against plant diseases (Ma,2004; Hammerschmidt, 2005), but only one publishedexample against insects (Gomes et al., 2005).

Silicon may act either directly or indirectly on insectherbivores (Kvedaras & Keeping, 2007). Direct effectsmay include a reduction in insect growth and repro-duction with concomitant reduction in damage to thecrop. Numerous studies have shown enhanced resistanceof host plants treated with Si to insect herbivores andother arthropods, mostly at two-trophic levels (Djamin& Pathak, 1967; Moraes et al., 2004, 2005; Kvedaraset al., 2007a,b, 2009; Kvedaras & Keeping, 2007). Indirecteffects are those affecting insect mortality rates and mayresult from delayed or reduced plant penetration, result-ing in increased exposure to natural enemies, adverseclimatic conditions and control measures that targetexposed insects, such as chemical applications (Kvedaras& Keeping, 2007). Indirect effects of Si may also occurthrough increased tolerance of plants to abiotic stresses,for example water stress, thus resulting in enhanced plantresistance to insect attack (Kvedaras et al., 2007a). Recentstudies in Australia have also highlighted the potential forSi to act indirectly at the third trophic level by increasingthe attraction of the natural enemies of an herbivorousinsect (Kvedaras et al., 2008; Kvedaras et al., 2009a).

Naturally occurring plant Si is a vital area to recogniseas the discovery of this association has led the way forapplied Si amendments to enhance plant resistance toinsect herbivores. O’Reagain & Mentis (1989) proposedthat leaf silicification in grasses evolved in response toinvertebrate herbivory and that it is primarily aimed atreducing tissue loss. They suggested that the histologicaldistribution of Si may inhibit small herbivore attack in

three ways. Firstly, bands of Si bodies may protect theunderlying vascular tissue restricting chewing or raspingherbivores to intercostal zones. Secondly, the silicifica-tion of epidermal cell walls may resist entry in theseareas. Thirdly, chewing herbivores may be inhibited frompenetration by silicification of the leaf margins. Althoughevidence that supports the role of Si in the physicaldefence of plants against arthropods continues to grow, itwas not until the work of Belanger et al. (1995) and Faweet al. (1998), that the role of Si in amplifying the chemicaldefences of plants first became apparent. Fauteux et al.,(2005) proposed that Si may play two central roles in plantchemical defence: (a) enhanced signal transduction at thesingle cell level leading to an increase in induced systemicresistance and (b) modulation of the generation of sys-temic signals, as both processes rely on primary elicitation.

Silicon may be applied as a post-harvest treatmentagainst a broad range of agricultural and environmentalpests. Such treatments include novel silicon-containinginsecticides with activity against various species of termiteand wood boring beetle in wood products (Adamset al., 1995) and diatomaceous earth (a dust powderformulation with silicon oxide) used as a dust toxicantagainst stored-grain insects (El-Lakwah et al., 2001; Lord,2001). In this paper, however, we review the role of Sias a pre-harvest treatment against herbivorous insects, attwo and three-trophic levels and the possible defencemechanisms involved, addressing only those studiesthat have applied Si either via the roots or as a leafsurface (foliar) application. Although the effect of Si onplant growth is particularly obvious under conditionsof stress, it is increasingly apparent that Si is involvedin complex defence mechanisms, most of which remainto be fully elucidated. Although several comprehensivereviews have covered the role of Si in disease resistance,there have been no such reviews of the role of Si in insectherbivore resistance in the peer-reviewed literature. Thispaper provides the first overview of such studies, whilehighlighting novel, recent hypotheses and findings.

Two-trophic level studies

Silicon sources and insect resistance

Various sources (or carriers; see Savant et al., 1999) of Sihave been used to deliver Si to the plant and test theefficacy of Si in enhancing host plant resistance to insects.These sources essentially fall into two classes: solid sourcesincorporated into the soil and silicate solutions applied asa soil drench or as a foliar spray.

Calcium silicate (Ca2SiO4) (as an industrial slag by-product and from geological sources such as wollastonite(calcium meta-silicate; CaSiO3)) has been a frequently

172 Ann Appl Biol 155 (2009) 171–186 © 2009 The AuthorsJournal compilation © 2009 Association of Applied Biologists

O.L. Reynolds et al. Silicon and insect herbivores

chosen source for direct incorporation into the soilin experimental interaction studies between plant Sifertilisation and a range of insect herbivores includingstem borers (Anderson & Sosa, 2001; Keeping &Meyer, 2002; Kvedaras et al., 2007b), phloem feeders(Correa et al., 2005; Goussain et al., 2005), and folivores(Korndorfer et al., 2004; Redmond & Potter, 2007). In allcases, except the two studies cited above on folivores,the calcium silicate applications produced significantreductions in insect performance and plant damage.Where silicate applications had no effect on insectperformance and damage, they nevertheless elevatedthe leaf Si content (Korndorfer et al., 2004; Redmond& Potter, 2007). Among these studies, the amountof plant available Si in the calcium silicate variedbetween 10% and 39%, with the product suppliedat rates between 1.12 and 10.0 t ha−1 (Gomes et al.,2005; Keeping & Meyer, 2006; Redmond & Potter,2007). Calcium silicate has also been applied in aqueoussolution as a foliar spray against whitefly, Bemisia tabaci(Gennadius) (Homoptera: Aleyrodidae) (1.0% solutionof ∼29% Si; Correa et al., 2005) and thrips, Thrips palmiKarny (Thysanoptera: Thripidae) (1.5% solution of ∼8%Si; Almeida et al., 2008), with significant reductions ininsect performance (Correa et al., 2005; Almeida et al.,2008) and plant damage (Almeida et al., 2008). Forsugarcane/insect studies, bagasse furnace ash (or flyash,a common by-product of sugar mills produced fromcomplete burning of bagasse) has also been used asa Si source for direct incorporation into the soil (Panet al., 1979; Keeping & Meyer, 2006). Fly ash is aninorganic source of calcium silicate, which includessmaller quantities of potassium silicate, sodium silicateand magnesium silicate, as well as about 40% carbon(dry weight). Porous hydrate calcium silicate applied toturf grass (hybrid type of Zoysia japonica Steud. and Zoysiamatrella (L.) Merr., cv. Miyako) produced a significantincrease in wear resistance of the turf and a 41% decreasein feeding by lawn cutworm, Rusidrina depravata Butler(Lepidoptera: Noctuidae) (Saigusa et al., 1999). Keeping& Meyer (2006) compared the effects of four Si sourcesincorporated in solid form, on Si uptake and resistanceof sugarcane to Eldana saccharina Walker (Lepidoptera:Pyralidae); calcium silicate from the USA (12% pureSi; supplied by Calcium Silicate Corp®, Lake Harbour,FL); wollastonite (12% Si; calcium meta-silicate, a by-product of the ceramics industry); Slagment® (18% Si;a blast-furnace slag supplied by Slagment Ltd., Alberton,South Africa), and flyash (10% Si). Silicon source hada large impact on both plant uptake of Si and onthe effect of Si on E. saccharina. For example, flyash at30 t ha−1 was less effective than calcium silicate at 10 tha−1 in reducing E. saccharina infestation. Furthermore,

although Slagment® at a rate of 10 t ha−1 releasedmore than three times as much Si into the soil thanthe USA calcium silicate, this greater release was notreflected as increased leaf and stalk Si content, or greaterreduction in borer performance and damage comparedwith calcium silicate. Such studies demonstrate thatalthough some sources provide large amounts of Si, muchof it may be unavailable to the plant, possibly becauseof re-polymerisation of silicic acid at high concentrationsfollowing its initial solubilisation in the soil (Keeping &Meyer, 2006).

Sodium silicate (Na2SiO3) solution has been aneffective liquid source of Si in numerous Si/insectinteraction studies, either applied to the growth mediumas a soil drench (Basagli et al., 2003; Moraes et al.,2004), or as foliar sprays alone (1, 2, and 4%;Hanisch, 1981) or as foliar sprays (0.5% or 1% SiO2)in combination with the soil drench (Moraes et al.,2004, 2005). Significant reductions in insect performancewere obtained, confirming that the Si source hadan effect (direct and/or indirect) on the target pest.For example, green bug Schizaphis graminum (Rondani)(Homiptera:Aphididae) reared on sodium-silicate-treatedsorghum plants showed a reduction in feeding preferenceand reproduction (Carvalho et al., 1999). Althoughapplication of sodium silicate and aphid pre-infestationdid not influence mortality and duration of the pre-reproductive and reproductive period of Schiz. graminumon sorghum plants, fewer aphids chose leaf sections ofplants subject to aphid pre-infestation or treated withsodium silicate (Costa & Moraes, 2002), and aphidcolonisation of sodium-silicate-treated sorghum plantswas also reduced (Moraes & Carvalho, 2002). In wheat,sodium silicate application reduced Schiz. graminumlongevity and nymph production, as well as plantpreference (Basagli et al., 2003). Italian ryegrass (Loliummultiflorum L., cv. RvP) fertilised with sodium silicatedisplayed a significant reduction in colonisation by thedipterous stem-boring larvae of Oscinella frit L. (Diptera:Chloropidae) and other related species (Moore, 1984).

To our knowledge, potassium silicate (K2SiO3) hasbeen used as a soil drench in only two publishedstudies investigating the effects of applied Si on insectherbivores: one on stem borer, Scirpophaga (Tryporyza)incertulas (Walker) (Lepidoptera: Pyralidae) in rice(Subbarao & Perraju, 1976) and the other on leafminer, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)in chrysanthemums (Parrella et al., 2007). In both,significant reductions in insect performance and increasedplant uptake of Si were recorded (Subbarao & Perraju,1976; Parrella et al., 2007).

The effectiveness of foliar spray- versus root-appliedsoil drenches is discussed further below.



Historical background to the role of Si in insectresistance

McColloch and Salmon (1923) were the first to sug-gest that silica played a role in the resistance of maize tohessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyi-idae). Later, Ponnaiya (1951) indicated that resistancein sorghum to central shoot fly, Atherigona indica infus-

cata Emden (Diptera: Muscidae) was related to Si. Thefirst study that showed an increase in plant resistanceto an insect as a result of Si application was that onrice stem borer, Chilo simplex Butler (Lepidoptera: Pyral-idae) (Sasamoto, 1953). Slag applied to rice plants inJapan reduced Ch. simplex damage and increased growthimpetus of the plant (Sasamoto, 1953), likely because ofincreased strength of the rice stem following Si accu-mulation (Sasamoto, 1955). Thereafter, studies haveincreasingly shown enhanced plant resistance to insectherbivores in a range of crops fertilised with Si, witha growing focus on determining the underlying mech-anism/s. More recently, Nakata et al., (2008) elegantlydemonstrated that Si accumulation by rice is involved inresistance to pests. They found that chewing damage fromrice leaf roller, Cnaphalocrocis medinalis (Guenee) (Lep-idoptera: Pyralidae) and rice green caterpillar, Naranga

aenescens Moore (Lepidoptera: Noctuidae) was apparentin leaves of the low silicon rice 1 (lsil) mutant clonedby Ma et al., (2006), which controls Si accumulation inrice, but not in the wild type plant. Thus the mutantcannot acquire resistance to biotic stressors even underfield conditions in which Si is at a high level.

Insect feeding guilds

Massey et al., (2006) postulated that plant Si was effectivein defending against folivorous but not phloem-feedinginsects. Such a differential effect of silicon between insectfeeding guilds was contested by Keeping & Kvedaras(2008). Previous studies have demonstrated a clear effectof plant Si on a range of insect feeding guilds, includ-ing lepidopteran borers (e.g. Chilo suppressalis Walker(Crambidae) (Nakano et al., 1961), Ch. infuscatelus Snell(Crambidae) (Rao, 1967), Diatraea saccharalis (Fabri-cius) (Crambidae) (Anderson & Sosa, 2001), Sesamiacalamistis Hampson (Noctuidae) (Setamou et al., 1993),Cn. medinalis (Sudhakar et al., 1991), Scirpophaga excerptalis

Walker (Pyralidae) (Gupta et al., 1992) and E. saccharina

(Kvedaras et al., 2007a,b; Kvedaras & Keeping, 2007),folivores (e.g. Spodoptera exempta Walker (Lepidoptera:Noctuidae) and Schistocerca gregaria Forskal (Orthoptera:Acridoidea) (Massey et al., 2006), phloem-feeding insects(e.g. Schiz. graminum (Rondani) (Hemiptera: Aphididae)(Basagli et al., 2003; Moraes et al., 2004), Laodelphax

striatellus Fallen (Hemiptera: Delphacidae) (Liu et al.,2007), Sitobion avenae (F.) (Hemiptera: Aphididae), andMetopolophium dirhodum (Walker) (Hemiptera: Aphididae)(Hanisch, 1981), some xylem-feeding insects (e.g. Nila-parvata lugens Stal. (Homoptera: Delphacidae)) (Yoshihara& Sogawa, 1979), and other plant feeders (e.g. Cylasformicarius Fab. (Coleoptera: Curculionidae) (Singh et al.,1993). In a later study, Massey et al., (2007) found thatthe phloem feeder, Si. avenae, suffered no detrimentaleffects from increased plant Si.

Nutritional and physical defences

The most widely accepted mechanisms for the actionof Si in increasing plant resistance to insect attackare reduced digestibility and increased hardness andabrasiveness of (especially epidermal) plant tissuesbecause of silica deposition, mainly as opaline phytoliths,and in association with cell walls (Kaufman et al., 1985;Salim & Saxena, 1992; Panda & Khush, 1995; Ma et al.,2001; Massey et al., 2006; Massey & Hartley, 2009). Thesemay affect the herbivore either directly or indirectly.

Nutrition

Elevated levels of Si may increase the bulk density ofthe diet such that insects are unable to ingest sufficientquantities of nutrients and water (Panda & Kush, 1995).For example, Massey et al., (2006) showed that Sp. exemptafed on high-Si plants of three (out of five) grass species notonly suffered reduced digestion efficiency, but increasedits rate of consumption on two (of the five) grassspecies only. Possibly, more specialist feeders such asSp. exempta have limited ability to increase consumptionto compensate for feeding on poorer quality host plants(Lee et al., 2003). Massey & Hartley (2009) subsequentlyfound that Si reduced both the efficiency with whichSp. exempta converted ingested food into body massand the amount of nitrogen absorbed from the diet.Increased consumption of plant material as a result ofpoor dietary quality has been reported for Sp. eridania(Cramer) (Lepidoptera: Noctuidae) (Peterson et al., 1988)and Schis. gregaria (Massey et al., 2006). However, silicamay also alter the palatability of plant material and deterherbivore feeding, as shown by Massey et al., (2006) forSchis. gregaria and Sp. exempta fed on grass species in whichuptake of Si produced increased leaf abrasiveness.

Other studies have also shown reduced consumptionwhen feeding on high-Si plants. Salim & Saxena (1992)observed decreased rice consumption by white-backedplanthopper, Sogatella furcifera (Horvath) (Homoptera:Delphacidae) fed on susceptible rice cultivars high in Si,in addition to reduced growth, adult longevity, fecundityand population increase. Chu & Horng (1991) noted that



slag-treated corn plants had harder stems, and consump-tion of the leaves (from Si-treated and untreated plants)by Asiatic corn borer Ostrinia furnacalis was negativelycorrelated with tissue hardness, indicating that Si-basedleaf hardness may be a factor in resistance to this borer.However, stem and sheath consumption was not affectedby the treatments. A reduction in stalk damage and lar-val weight gain (as a result of decreased consumption)was shown for stem borer E. saccharina fed on Si-treatedsugarcane compared with untreated sugarcane (Keeping& Meyer, 2006; Kvedaras et al., 2007b).

In Ost. furnacalis Guenee (Lepidoptera: Crambidae)reared on artificial diet, mortality of larvae and pupaeincreased, pre-oviposition period was prolonged and theoviposition period was shortened as the diet Si contentwas increased from 0.1, to 3, 5 or 10% (Horng & Chu,1990). Pupal weight, fecundity, net reproductive rate andintrinsic rate of increase were all negatively correlatedwith diet Si content. However, the duration of larval andpupal stages, longevity of adults and mean generationtimes were not significantly affected.

Silicon may counteract the effects of high plant N levelsin promoting insect performance. In potted corn (Zea maysL.), Chu & Horng (1991) observed decreased preferenceunder free-choice conditions of Ost. furnacalis for slag-treated (i.e. Si-treated) plants but increased preference forhigh-nitrogen-treated plants. Meyer & Keeping (2005)later showed that the application of soil-applied Sican mitigate the promotional effects of applied N onpopulations of the stalk borer, E. saccharina in sugarcane.They postulated that the use of Si would enable growers,who had reduced their N application rates because ofincreased E. saccharina infestations, to resume applyingthe recommended rates of N, thus ensuring that N wouldnot limit the crop yield.

Physical defences

In larval Lepidoptera, mandibular wear is often attributedto plant Si (sometimes based only on visual comparisonsbetween high-Si and low-Si plants or tissue) and has beenreported for rice stem borer Ch. suppressalis (Sasamoto,1958; Djamin & Pathak, 1967; Drave & Lauge, 1978)and leaf folder larvae Cn. medinalis (Hanifa et al., 1974;Ramachandran & Khan, 1991) fed on rice and for fallarmyworm, Sp. frugiperda, fed on corn plants (Goussainet al., 2002). However, these studies and most otherreports of Si causing mandibular wear of arthropods haveshortcomings (Smith et al., 2007; Kvedaras et al., 2009b)and are therefore not compelling in their conclusions.For example, although Drave & Lauge (1978) useda quantitative, statistical approach to compare larvalmandibular wear of Ch. suppressalis, their Si treatments

were applied in artificial diet, rather than in planta,

thereby removing the natural context under which

the insect would encounter Si when feeding on the

plant. Similarly, Zouhourian-Saghiri et al.’s (1983) study,

although quantitative, did not employ Si treatments (and

untreated controls) of the same plant material to exclude

the likely contribution of cellulose and lignin (within

their high-Si plant material, Sasa japonica) to mandibular

wear in Locusta migratoria (Orthoptera: Acrididae).

Redmond & Potter (2007), showed that calcium silicate

fertiliser (Excellerator™, Excell Minerals, Sarver, PA)

applied to ’Penncross’ creeping bentgrass caused no

excessive wearing of mandibular teeth in black cutworm,

Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) and

root-feeding masked chafer grubs, Cyclocephala spp.

(Coleoptera: Scarabaeidae). There are only two studies

that have attempted to accurately quantify the effect of

experimentally elevated plant Si on mandibular wear

in insects. Kvedaras et al., (2009b) showed only a non-

significant trend for greater mandibular wear in E.

saccharina larvae fed on sugarcane cultivars treated with

Si compared with untreated controls. However, Massey

& Hartley (2009) demonstrated a significant and rapid

(within a single instar) increase in mandibular wear for

Sp. exempta fed on two out of three grass species fertilised

with Si, compared with untreated controls. A difficulty in

measuring mandibular wear in Lepidoptera is that larvae

replace their mandibles at each moult. Plants high in Si

may force larvae to moult sooner than usual, because

of increased mandibular wear, which may in turn lead

to decreased body weight. This is an area that merits

additional study, as the time spent in a given instar

would probably affect the degree of mandibular wear and

resulting long-term performance of the herbivore.

Recently, Hunt et al., (2008) concluded that silica may

defend grasses, at least in part, by mechanical protection

of resources in the chlorenchyma cells (which contain

high levels of starch and protein sought after by insects),

through reduced mechanical breakdown of the leaf. They

demonstrated that high-silica grasses released less chloro-

phyll after grinding and retained more after passing

through the gut of the locust, Schis. gregaria, illustrating

that Si levels are correlated with increased mechanical

protection.

Using scanning electron microscopy and X-ray micro-

analysis Keeping et al., (2009) showed that in two sug-

arcane cultivars, Si-treated plants had increased silica in

the stalk epidermis, particularly at the internode and root

band. As these are known penetration sites for E. sac-

charina borer, such patterns of Si deposition may partly

explain the enhanced resistance of Si-treated sugarcane

to borer penetration and feeding. However, Keeping et al.



(2009) conceded that fibre content (cellulose, hemicel-lulose and lignin) is probably also crucial in this regard(more so in resistant cultivars; Rutherford et al., 1993).In maize, for example, Coors (1987) demonstrated thatgenotypes most resistant to European corn borer Ost.nubilalis (Hubner) had high levels of total structural car-bohydrates, lignin and silica.

Although numerous studies have looked at the directphysical effects of Si on insect herbivores (see above),there have been few studies that have looked at theindirect effects. Kvedaras & Keeping (2007) showed thatSi delayed the penetration of the sugarcane stalk by E.saccharina, which they proposed may lead to increasedexposure time of young larvae to adverse environmentalconditions or control practices that target such larvae.Similarly, when yellow stem borer, Sci. incertulas, larvaewere fed on rice grown in a high Si nutrient solution,penetration time increased compared with a low level ofSi (IRRI, 1990, cited by Savant et al., 1997). Feedingand boring by Ch. suppressalis larvae is also impededin rice grown in silica (Djamin & Pathak, 1967). Afurther indirect effect (and to our knowledge, the onlyexample to date of an interaction between Si-mediatedresistance to an insect herbivore and an abiotic stressfactor) was illustrated by a reduction in E. saccharinanumbers and stalk damage in Si-fed but water-stressedcane plants (Kvedaras et al., 2007a). Further, the increasein resistance of Si-treated water-stressed susceptiblecultivars to E. saccharina was such that borer survivaland damage in these plants approached, and in almostall instances, was not significantly different from that ofresistant cultivars (irrespective of whether the latter weretreated with Si and/or water stressed). Possibly, in thepresence of Si, water-stressed borer-susceptible cultivarsmay develop a defensive chemistry with a profile similarto that of borer-resistant cultivars. These results parallelother studies, where the effect of Si on plant disease ismore pronounced under conditions of abiotic stress thannon-stressed conditions (Ma et al., 2001; Ma, 2004; Gonget al., 2005; Wiese et al., 2005). Such observations suggestthat Si application could provide enhanced herbivoreresistance to plants exposed to a range of abiotic factors,including salinity stress and heavy metal toxicity.

In both an insect (the locust, Schis. gregaria) and amammalian herbivore (the field vole, Microtus agrestisL. (Rodentia: Muridae), Massey et al., (2007) revealedthat repeated damage events led to the induction ofincreases of c. 400% in foliar Si levels of two grass species,compared with undamaged plants and attributed this toeither increased Si uptake from the soil or increaseddeposition of phytoliths, or both. Single damage eventsor mechanical defoliation, however, were not sufficientto promote induction responses in either grass species.

Furthermore, the authors showed that the elevated Siconcentration in grass leaves as a result of herbivorydeterred further feeding. These results are not surprisingas it is recognised that artificial damage can elicit differentinduction responses to those of herbivory, and in insects,salivary gland secretions and regurgitants have beenidentified as the sources of cues leading to plant responsesto herbivory (see review by Felton & Eichenseer, 1999).

Location and composition of Si in the plant

Several studies suggest that the site and arrangement ofSi deposition in the plant are more important than Sicontent per se in restricting larval feeding. Miller et al.,(1960) demonstrated that the leaf sheaths of certainwheat cultivars, as well as one cultivar of oats, whichare resistant to hessian fly Phytophaga destructor (Say)(Diptera: Cecidomyiidae), displayed a more completeand even distribution of silica deposits on their surfacethan those of susceptible cultivars (Miller et al., 1960).The authors proposed that this arrangement may allowP. destructor larvae to feed between the rows of Si andshowed that in certain resistant cultivars there may notbe sufficient free space to allow unobstructed feedingby larvae. Blum (1968) found that in five cultivars ofsorghum resistant to the sorghum shoot fly, Atherigona

soccata (Rondani) (Diptera: Muscidae), the density ofsilica bodies present in the abaxial epidermis at thebase of the first, second and third leaf sheaths (thearea where the insect penetrates the plant) was greaterthan in a susceptible cultivar. Similarly, a study on ricerevealed that the pattern of silica in the epidermis ofcultivars resistant to the leafroller, Cn. medinalis comprisedcloser silica chains, heavier deposition of silica in theintercostal area, higher epidermal silica deposition, andsingle or double rows of silica in comparison withsusceptible cultivars (Hanifa et al., 1974). As the totalSi content of resistant and susceptible cultivars did notdiffer significantly, the physical arrangement and locationof Si in the plant tissues were considered to be important(Miller et al., 1960; Hanifa et al., 1974). Barker (1989)showed that high densities of silica deposits (inclusive oftrichomes) in the sheath epidermis of ryegrass cultivarshindered oviposition by the weevil, Listronotus bonariensis

(Kuschel) (Coleoptera: Curculionidae). The closely spacedrows of silica cells in the leaf epidermal layer is thoughtto be partly responsible for the greater resistance ofwild rice to Cn. medinalis compared with the widerspacing in a rice hybrid (Ramachandran & Khan, 1991).A rice cultivar resistant to white-backed plant hopper,S. furcifera not only had higher concentrations of Si butsilicated bulliform cells were closer and double in numbercompared with a highly susceptible cultivar (Mishra &



Misra, 1992). In a study comparing ryegrass cultivars(hybrid type of Zoysia japonica Steud. with Z. matrella

(L.) Merr., cv. Miyako) resistant and susceptible to larvaeof Osc. frit, Moore (1984) observed that the resistantcultivar had silica bodies scattered over the pseudostem,but in the susceptible cultivar they were often indiscrete rows. This may explain why small increasesin plant silica levels correspond to large reductions inthe number of larvae found (Moore, 1984). Kvedaraset al., (2007b) suggested this could also be true forE. saccharina on sugarcane. Rao & Panwar (2001), incomparing maize cultivars, either resistant, moderatelyresistant or highly susceptible to shoot fly species A. soccata

and A. naqvii Steyskal, showed that the lignified vascularbundles and leaf epidermal silica bodies were negativelycorrelated with oviposition and dead-heart percentages,and that the resistant cultivars had a higher number oflignified vascular bundles as well as leaf epidermal silicabodies compared to susceptible cultivars. Agarwal (1969)reported that sugarcane Saccaharum spontaneum L. cloneswith higher numbers of silica cells in the wax band ofthe internode had significantly lower levels of sugarcanescale, Melanaspis glomerata (Green) (Homoptera: Coccidae)infestation.

Chemical defence

As early as 1958, Sasamoto suggested that host choice byan insect depended not only on the physical propertiesof the food but also on its chemical properties. In alaboratory choice study, Sasamoto (1958) demonstratedthat larvae of the rice stem borer, Ch. suppressalis displayeda preference for untreated rice stalks over Si-treatedrice stalks, and that larvae from the latter showedincreased mandibular wear (see previous section).Notably, water extracted from the stem of the rice plantcultured in nitrogen-rich manure was more attractiveto larvae than the silicated one. Recently, Zadda et al.,(2007) showed that the application of organic sourcesof nutrients and amendments (farm yard manure,poultry manure, neem cake, mahua cake, pungamcake and biofertilisers, i.e. Azospirillum, phosphobacteriaand silica solubilising bacteria) to eggplant, Solanum

melongena L., significantly enhanced the productionof defensive chemicals including silica and phenols.Further, the authors showed that induced resistanceby way of antibiosis led to a reduction in feedingrate, oviposition, longevity and population buildup andprolonged the nymphal duration of eggplant pests(Zadda et al., 2007).

Earlier, Goussain et al., (2005) showed that stylet pene-tration of Schiz. graminum was not impeded by Si in wheatplants; however, the stylet was withdrawn more often

resulting in a reduction of probing time, leading themto conclude that chemical changes because of Si absorp-tion by the plant were likely responsible, as opposed toa physical impediment, as the stylet eventually did reachthe phloem. Studies on Si-mediated resistance of cucum-ber to whitefly B. tabaci (Correa et al., 2005) and wheatto Schiz. graminum (Gomes et al., 2005) also suggest thatsoluble Si is important in induced resistance to insectherbivores, as has been shown for Si-mediated resis-tance induction of various crops to fungal pathogens (seereview by Fauteux et al., 2005). Research on the inter-actions between plant defences, Si and fungal pathogenshas shown that the presence of a pathogen is pivotalin the mobilisation of biochemical defences and in theupregulation of defence-related genes; some of the lat-ter are involved in the biosynthesis of herbivore-inducedplant volatiles (HIPVs), including jasmonate (JA) andsalicylate (SA) (Thaler et al., 2002; Fauteux et al., 2005,2006). HIPVs are released in response to herbivore dam-age to facilitate location by natural enemies of plantswhere their prey or hosts are present (see review byDicke et al., 2003 and later section on tri-trophic inter-actions). Work in the USA has shown that plant-derivedor synthetic versions of these chemical cues (HIPVs)will attract beneficial insects into treated crops (Khanet al., 2008). Silicon, either alone or together with Schiz.graminum pre-infestation, elicited a significant increasein the defensive enzymes, peroxidase, polyphenoloxi-dase, and phenylalanine ammonia-lyase (PAL), activityin wheat (Gomes et al., 2005). Peroxidase is involved inthe process of lignification and suberin synthesis, whichincrease the hardness of tissues and in the productionof quinones and active oxygen that possess antibioticproperties (Goodman et al., 1986; Bowles, 1990; Stoutet al., 1994). Polyphenoloxidase catalyses the oxidation ofphenolic compounds to quinones that leads to a reduc-tion in the nutritional quality of the food and decreasedprotein digestibility (Felton & Duffey, 1990; Felton et al.,1994). The PAL enzyme increases the production of phe-nolic compounds that have anti-nutritional, deterrentand toxic properties (Appel, 1993). Many mechanismsof defence are shared with those against fungi (Goussainet al., 2005), and as the bulk of the work thus far onSi and induced chemical defence has been carried outin this area, it may be that future research will revealsimilar defensive mechanisms at work in both fungi andinsects.

Nil effects of Si on herbivores

In India, Agarwal (1969), using morphological studies,was unable to demonstrate any relationship betweenthe number of silica cells in sugarcane clones and



infestation by whitefly Aleurolobus barodensis Mask.and Neomaskellia bergii Sign. (Homoptera: Aleyrodidae).Application of calcium silicate to five different turf grassesdid not negatively affect the growth and developmentof tropical sod webworm, Herpetogramma phaeopteralisGuenee (Lepidoptera: Pyralidae), despite increased Silevels in the plant tissue (Korndorfer et al., 2004). Prilledcalcium silicate fertiliser (Excellerator™, Excell Minerals,Sarvar, PA) applied to fairway-height turf on silt loamsoil elevated leaf Si by as much as 40% without reducingthe palatability or suitability for the black cutworm, A.ipsilon, nor did Si reduce the density or weight of root-feeding masked chafer (Cyclocephala spp.) grubs (Redmond& Potter, 2007). Similarly, sodium silicate drenches thatelevated leaf Si content of greenhouse-grown bentgrassfrom 0.5 to 2.5% did not reduce A. ipsilon feeding orsurvival and had little effect on larval growth rates(Redmond & Potter, 2007).

Chaudhary & Yadav (1998) found no correlationbetween the incidence of top borer, Sc. excerptalis andthe presence of silica, cellulose, lignin and ash present inmidribs, growing points and leaf blades of 30 sugarcanegenotypes, despite a large variation in all but the lignincontents of midribs, growing points and leaf blades.In International Rice Research Institute and new planttype (NPT) rice cultivars, Sunio et al., (2000) could notshow a correlation between silica content and percentagewhiteheads and percentage dead hearts caused by stemborers (mainly Ch. suppressalis). Although Hanisch (1981)showed that infestation of nitrogen-fertilised wheat plantsby Si. avenae and M. dirhodum was reduced, throughapplication of a 1% sodium silicate foliar spray, tobelow that in nitrogen-deficient control plants, apparentlybecause of the uptake of silica in the leaves of sprayedplants, Massey et al., (2007) found that the same phloem-feeding insect, Si. avenae, suffered no detrimental effectsof feeding on five different grasses with naturally highlevels of Si.

Mebrahtu et al., (1988) could not demonstrate anycorrelation between the silicon content of soya beans andthe pupal weight of the Mexican bean beetle, Epilachnavarivestis Mulsant (Coleoptera: Coccinellidae). In threepineapple varieties, a significant positive correlation wasfound between Si and the population density of thepineapple flat mite, Dolichotetranychus floridanus (Banks)(Acarina: Tenuipalpidae) (although not an insect, buta member of the Phylum Arthropoda) (Das et al.,2000). There may be many more studies that remainunpublished on the failure of Si to reduce insect herbivoreperformance, as these are often regarded as not worthyof publication, but would assist us in identifying anytrend in how plant Si may differentially affect insectsbelonging to different groups or feeding guilds, for which

at present there is no convincing evidence (Keeping &Kvedaras, 2008).

Silicon, solubilisers and other control agents

It has been demonstrated that molecules such as pyridine-N-oxides can enhance the solubility of Si in water and thesubsequent physiological effects on yellow stem borer,Sci, incertulas (Walker) (Lepidoptera: Pyralidae) damageand rice blast disease, Magnaporthe grisea (Ranganathanet al., 2006). However, more recently Voleti et al., (2008)showed, using scanning electron microscopy and Simapping, that simple amino acids (natural Si solubilisers)such as histidine or glycine can significantly enhance thelevels of Si(OH)4 in the stem and increase Si deposition inthe leaf. This is important progress because pyridine-N-oxides are organic molecules that may have soil residualeffects harmful to soil microorganisms, unlike the naturalSi solubilisers identified above. Subsequently, a novelclass of biocompatible molecules has been identifiedthat exhibit remarkable resistance to damage caused bythe yellow stem borer, Sci. incertulas and blast infectionsin rice, in addition to high levels of dry matter andincreased yields. In a free-choice test, Si, the insect growthregulator lufenuron, and their interaction did not affectthe preference of Sp. frugiperda on maize; however, whenboth were combined in a non-choice test, better controlof Sp. frugiperda was obtained compared with lufenurononly (Neri et al., 2005). Tomquelski et al., (2007) showedthat both acibenzolar-S-methyl (BTH) and Si appliedindependently to cotton, reduced the larval period andpupal weight and increased the pupal period of Alabamaargillacea (Hubner) (Lepidoptera: Noctuidae). Recently,Gomes et al., (2008a) demonstrated that the combineduse of Si and a half dose of the insecticide imidaclopridreduced the colonisation of potato plants by the aphid,Myzus persicae (Sulzer) to the same extent as the insecticidealone. This prompted the authors to propose that Siapplication could potentially form part of an IntegratedPest Management (IPM) program for potatoes. A furtherstudy that year showed that although Si fertilisation didnot affect M. persicae preference, it did reduce the fecundityand the rate of population growth of the insects (Gomeset al., 2008b).

Silicon and plant cultivars

Although the bulk of our discussion has focussed on Siamendments, the discovery of the association betweenendogenous levels of plant Si and resistance to insects hasled the way for applied Si amendments to enhance plantresistance to insect herbivores. Elevated plant Si levelsor higher densities of Si bodies are frequently reported



from plant cultivars that have high or increased levels ofresistance to insect attack. This has been demonstratedfor aubergine (brinjal/eggplant) (Jat & Pareek, 2003),barley (Guslits, 1990; Sinel’nikov & Shapiro, 1990),cotton (Taneja et al., 1988), cotton and okra (Singh &Agarwal, 1988), chickpea (Rupali et al., 2003), maize(Sekhon & Kanta, 1997; Smith, 1997; Rao & Panwar,2001), citrus (orange) (Matichenkov et al., 2000), rice(Sujatha et al., 1987; Anuradha et al., 1988 a,b; Dan &Chen, 1990; Mishra et al., 1990; Sudhakar et al., 1991;Mishra & Misra, 1992, 1993; Lin, 1993; Soliman et al.,1997; Saeb et al., 2002), sorghum (Narwal, 1973; Chavanet al., 1990; Dalvi et al., 1990), sugarcane (Kennedy &Nachiappan, 1992; Keeping & Meyer, 2006), sweet potato(Singh et al., 1993) and turmeric (Lakshmi & Sudhakar,2003). Clearly, however, Si is only one factor that actsto enhance cultivar resistance to insects, along with amultitude of other physical and chemical traits that havebeen documented in the plant resistance literature.

Foliar- versus root-applied Si

A number of studies have showed increased plantresistance to biotic stress after the application of Si foliarsprays. Hanisch (1981) reported that the deposition andincreased solubility of Si in the leaves of wheat plants afterfoliar sprays of a 1% Na2SiO2 solution were responsiblefor the resistance of this crop to the aphids M. dirhodumand Si. avenae. The author showed that the number of haircells containing silica in the epidermis of plants treatedwith sodium silicate was 70% greater than in untreatedones, indicating the uptake and translocation of silicain the leaves of foliar sprayed plants. Foliar applicationof lignite fly ash dust, which is high in silica content,to papaya led to a significant reduction in the disease,papaya leaf curl virus, and in vector, silverleaf whitefly,B. tabaci populations (Eswaran & Manivannan, 2007).

Studies have also compared the application of Sias both a foliar spray and via the soil. For example,Moraes et al., (2005) showed that the number of cornleaf aphids, Rhopalosiphum maidis (Fitch) (Hemiptera:Aphididae) on detached leaves of corn leaf plants wassignificantly reduced when the plants had been treatedwith either two foliar Si sprays or one application ofSi through the soil and an additional Si foliar spraycompared with plants treated with Si applied through thesoil or one foliar Si spray.

In a free-choice study on whitefly B. tabaci (Hemiptera:Aleyrodidae), Correa et al., (2005) reported that calciumsilicate incorporated in the soil resulted in a reducednumber of whitefly eggs on cucumber; however, themost striking effect was that of a foliar application ofcalcium silicate with or without the resistance inducer

BTH, which reduced oviposition more than three timesthat of the control. Both application methods of calciumsilicate and BTH resulted in increased developmentalperiod of second to fourth instar nymphs. Interestingly,Costa & Moraes (2006) showed that the application of Si(foliar- and soil-applied, although particularly the latter)or BTH, significantly reduced the number of nymphs, thepopulation growth rate, the post-reproductive period andthe longevity of Schiz. graminum on wheat plants, leadingthe authors to conclude that either would be encouragingcontrol methods in the IPM of the aphid in wheat. Ina later study on the same species, Costa et al., (2007)compared foliar Si application, BTH and both combined,and found that the latter two were less preferred byaphids than the foliar Si-treatment alone.

Some studies, whether using soil and/or foliar-appliedSi, have failed to measure plant Si levels following thetreatments to establish the extent of Si uptake (Basagliet al., 2003; Moraes et al., 2004; Gomes et al., 2005;Goussain et al., 2005). Such measurements are essentialin supporting causal arguments that the applied Si isacting on the insect through incorporation into the planttissue, as opposed to some extraneous pathway, and areespecially important with respect to foliar applications.Matlou (2006) concluded that foliar application of threesources of Si (including potassium silicate) at two ratesand including the use of a wetting agent was ineffectivein increasing leaf Si content of sorghum (a Si-responsivecrop) grown in low-Si soils, whereas the root-appliedcalcium silicate treatment produced significant increasesin leaf Si. Guevel et al., (2007) showed that at least forwheat plants Si is absorbed primarily, if not exclusively,by the root system. They noted that foliar sprays withboth Si and nutrient solutions are likely to have a directeffect on the plant, rather than one mediated by the plantas is the case for root amendments. However, this arearemains contentious as there is no firm evidence for theuptake of Si from the leaves (Guevel et al., 2007).

Tri-trophic interactions

Plants supplemented with Si translocate silicic acidthroughout their tissues and, when attacked bypathogens, produce systemic stress signals such as SAand JA (Fauteux et al., 2005) that are key to plant-induced defences (Gatehouse, 2002). Jasmonic acid, anaturally occurring growth regulator and wound hor-mone in higher plants, is particularly important becauseof its role in HIPV production. Silicon may have an effecton the plant’s ability to generate an induced response byacting not only at the second but also the third trophiclevel (i.e. by attracting predators or parasitoids). However,only one study has tested for the effect of Si on an insect



herbivore and the resultant attractancy of the insect’spredators and parasitoids (Moraes et al., 2004). That workshowed no effect of Si on natural enemies (detrimen-tal effects on the pest were shown however), but usednon-choice conditions in which parasitoid wasps, Aphid-

ius colemani Viereck (Hymenoptera: Aphidiidae) wererestricted on a small scale to individual wheat plantsthat were narrowly spaced. Further experiments con-ducted with the predator, Chrysoperla externa (Hagen)(Neuroptera: Chrysopidae) were still less favourable forthe detection of induced plant defences involving HIPVs,as the herbivore Schiz. graminum was removed from thetest plants and fed to predators that had not been exposedto plants at all (Moraes et al., 2004).

Work recently commenced in Australia, presented atthe IV Silicon in Agriculture Conference by Kvedaraset al., (2008), and since published (Kvedaras et al.,(2009a) has been designed to look at the attraction ofnatural enemies to Si-treated and untreated plants andis methodologically and conceptually more advanced.The application of Si with a subsequent pest infestationincreased the plants’ ability to mount an induced responseby attracting natural enemies. An effect that was reflectedin elevated biological control in the field. The potentialfor using Si fertilisation as an elicitor of induced plantchemical defences for attraction of biological controlagents in pest management is an exciting prospect.Moreover, if the promising results to date translate tothe availability of novel plant protection compounds thatpromote host plant resistance traits operating throughthe third trophic level it may prove to be less prone to adecrease in efficacy as a result of genetic adaptation of thetarget pest population (Gurr & Kvedaras, 2009). This is soas pest suppression is likely to occur through a numberof natural enemies capable of adapting in response to anyshift in pest phenotype.

Conclusions and future prospects

Although the discovery that Si plays a role in the resis-tance of plants to insect herbivores dates back to the early1950s, we are only in the very early stages of elucidatingthe mechanisms on which this is based. It seems fairlyclear that Si-mediated defences against insects are partlyphysical in nature and therefore based on solid amor-phous (opaline) Si deposited in key tissues and organsof the plant, where they are able to mechanically hinderinsect establishment, plant penetration and feeding effi-ciency, as well as to reduce palatability and plant tissuedigestibility. However, direct causal relationships betweenthe mechanical properties and effects of opaline silica andthe performance of insects feeding on high-Si plants are

difficult to demonstrate and there is still considerablescope in this area for worthwhile research.

Even less well explored is the likely role of soluble Siin induced plant defence against insect herbivores. Thelimited research that has been done in this area provides atantalising glimpse of how Si may be involved in inducedbiochemical defences that call into play various defensiveenzymes and defence-related plant hormones such asJA and SA. It has become clear that Si is critical as anameliorator of plant stress, whether biotic or abiotic, withpossibly little role in unstressed plants. The importanceof (drought) stress in amplifying the protective effectof Si against a stem borer has been demonstrated, andthis, together with clues provided by studies of ind-uced biochemical defence in Si × pathogen interactions(Menzies et al., 1992; Cherif et al., 1994; Fauteux et al.,2005) and two studies on Si and resistance inductionagainst insects in wheat and cucumber (Gomes et al.,2005; Kvedaras et al., 2009a), poses the questions: (a) Issoluble Si a key player in facilitating induced biochemicaldefences against insect herbivores? (b) Is Si involved inupregulation of defence-related genes (such as those inJA or SA biosynthesis) following insect attack? (c) Whileinsect attack is a source of stress for the plant, doadditional abiotic stresses in combination with Si leadto an even greater inducible response?

These are just a few of the many questions that willno doubt emerge as the field of Si-mediated defence ofplants against herbivores (invertebrate and vertebrate)progresses. Throughout this review we have attempted tohighlight some of the novel hypotheses and findings thusfar, while also indicating the shortcomings of researchin the area of Si and insect herbivory. We hope thatthis review may assist in providing pointers for furtherinvestigation into the challenging new areas of this fieldthat remain little explored or unexplored.

Acknowledgements

Lee-Anne McInerney is thanked for a literature searchand both Christine Harley and Lee-Anne McInerneyare thanked for sourcing many of the more obscurereferences. Fumi Chiku is thanked for the interpretationof the Japanese language articles and Ana Korndorferfor interpretation of Brazilian articles. We are gratefulto Geoff Gurr who provided useful comments onearlier drafts of the manuscript and to two anonymousreviewers.

References

Adams A.J., Jermannaud A., Serment M.M. (1995) Novel

chemistry and versatility for termite control. In Document



- International Research Group on Wood Preservation, p. 15,

Doc. No. IRG/WP 95-30069. Stockholm, Sweden: IRG

Secretariat.

Agarwal R.A. (1969) Morphological characteristics of

sugarcane and insect resistance. Entomologia Experimentalis

et Applicata, 12, 767–776.

Almeida G.D., de Pratissoli D., Zanuncio J.C., Vicentini V.B.,Holtz A.M., Serrao J.E. (2008) Calcium silicate and

organic mineral fertilizer applications reduce phytophagy

by Thrips palmi Karny (Thysanoptera: Thripidae) on

eggplants (Solanum melongena L.). Interciencia, 33,

835–838.

Anderson D.L., Sosa, O., Jr (2001) Effect of silicon on

expression of resistance to sugarcane borer (Diatraea

saccharalis). Journal of the American Society of Sugar Cane

Technologists, 21, 43–50.

Anuradha K., Nagalingam B., Raghavaiah G. (1988a)

Relative reaction of rice cultivars to Sitophilus oryzae

(Linnaeus). Seeds and Farms, 14, 42–45.

Anuradha K., Nagalingam S., Raghavaiah G. (1988b)

Differential reaction of rice cultivars to Rhizopertha

dominica. Oryza, 25, 169–173.

Appel H.M. (1993) Phenolics in ecological interactions: the

importance of oxidation. Journal of Chemical Ecology, 19,

1521–1552.

Barker G.M. (1989) Grass host preferences of Listronotus

bonariensis (Coleoptera: Curculionidae). Journal of

Economic Entomology, 82, 1807–1816.

Basagli M.A., Moraes J.C., Carvalho G.A., Ecole C.C.,Goncalves-Gervasio R. de C.R. (2003) Effects of sodium

silicate application on the resistance of wheat plants to

the green-aphid Schizaphis graminum (Rond.) (Hemiptera:

Aphididae). Neotropical Entomology, 32, 659–663.

Belanger R.R., Bowen P.A., Ehret D.L., Menzies J.G. (1995)

Soluble silicon: its role in crop and disease management

of greenhouse crops. Plant Disease, 79, 329–336.Blum A. (1968) Anatomical phenomena in seedlings of

sorghum varieties resistant to sorghum shoot fly

Atherigona varia socata. Crop Science, 8, 388–391.

Bowles D.J. (1990) Defense-related proteins in higher

plants. Annual Review of Biochemistry, 59, 873–907.

Carvalho, S.P., Moraes, J.C., Carvalho, J.G. (1999) Silica

effect on the resistance of Sorghum bicolor (L.) Moench tothe greenbug Schizaphis graminum (Rond.) (Homoptera:

Aphididae). Anais da Sociedade Entomologica do Brasil, 28,

505–510.

Chaudhary J.P., Yadav S.R. (1998) Effect of different levels

of cellulose, lignin, silica and ash contents available in

midribs, growing points and leaf blades of sugarcane

genotypes on incidence of top borer, Scirpophaga

excerptalis Walker (Lepidoptera: Pyralidae)-VIII.Cooperative Sugar, 29, 337.

Chavan M.H., Phadnawis B.N., Hudge V.S., Salunke M.R.

(1990) Biochemical basis of shoot-fly tolerant sorghum

genotypes. Annals of Plant Physiology, 4, 215–220.

Cherif M., Asselin A., Belanger R.R. (1994) Defense

responses induced by soluble silicon in cucumber rootsinfected by Pythium spp. Phytopathology, 84, 236–242.

Chu Y.-I., Horng S.-B. (1991) Infestation and reproduction

of Asia corn borer on slag-treated corn plants. Chinese

Journal of Entomology, 11, 19–24.

Coors J.G. (1987) Resistance to the European corn borer,

Ostrinia nubilalis (Hubner), in maize, Zea mays L., as

affected by soil silica, plant silica, structuralcarbohydrates, and lignin. In Genetic Aspects of Plant

Mineral Nutrition, pp 445–456. Eds W.H. Gabelman and

B.C. Loughman. Dordrecht, the Netherlands, Madison:

Martinus Nijhoff.

Correa R.S., Moraes J.C., Auad A.M., Carvalho G.A. (2005)

Silicon and acibenzolar-S-methyl as resistance inducers

in cucumber, against the whitefly Bemisia tabaci

(Gennadius) (Hemiptera: Aleyrodidae) biotype B.

Neotropical Entomology, 34, 429–433.

Costa R.R., Moraes J.C. (2002) Resistance induced in

sorghum by sodium silicate and initial infestation by the

green aphid Schizaphis graminum. Ecossistema, 27, 37–39.

Costa R.R., Moraes J.C. (2006) Efeitos do acido silıcico e do

acibenzolar-S-methyl sobre Schizaphis graminum

(Rondani) (Hemiptera: Aphididae) em plantas de trigo.

Neotropical Entomology, 35, 834–839.

Costa R.R., Moraes J.C., Antunes C.S. (2007) Resistencia

induzida em trigo ao pulgao Schizaphis graminum

(Rondani, 1852) (Hemiptera: Aphididae) por silicon e

acibenzolar-S-methyl. Ciencia e Agrotecnologia, 31,

393–397.Dalvi C.S., Dataya V.P., Khanvilkar V.G. (1990) Screening

of some sorghum varieties for resistance to shootfly

Atherigona soccata (Rondani). Indian Journal of Entomology,

52, 279–289.

Dan J.G., Chen C.M. (1990) Effects of feed condition on the

growth, development and reproduction of Cnaphalocrocis

medinalis. Acta Phytophylacica Sinica, 17, 193–199.Das T.K., Sarkar P.K., Dey P.K., Somchoudhury A.K. (2000)

The chemical basis of resistance of pineapple plant to

Dolichotetranychus floridanus Banks (Prostigmata:

Tenuipalpidae). Acarologia, 41, 317–320.

Dicke M., van Poecke R.M.P., de Boer J.G. (2003) Inducible

indirect defence of plants: from mechanisms to ecological

functions. Basic and Applied Ecology, 4, 27–42.Djamin A., Pathak M.D. (1967) Role of silica in resistance to

Asiatic rice borer, Chilo suppressalis Walker, in rice

varieties. Journal of Economic Entomology, 60, 347–351.

Drave E.H., Lauge G. (1978) Etude de l’action de la silice sur

l’usure des mandibules de la pyrale du riz: Chilo

suppressalis (F. Walker) (Lep. Pyralidae Crambinae).

Bulletin de la Societe Entomologique de France, 83, 159–162.El-Lakwah F.A., Mohamed R.A., El-Kashlan I.H. (2001)

Effectiveness of katel-sous, diatomaceous earth and their

joint action against three species of stored product insects.

Annals of Agricultural Science, Moshtohor, 39, 655–663.



Eswaran A., Manivannan K. (2007) Effect of foliar

application of lignite fly ash on the management ofpapaya leaf curl disease. Acta Horticulturae, 740, 271–275.

Fauteux F., Chain F., Belzile F., Menzies J.G., Belanger R.R.

(2006) The protective role of silicon in the

Arabidopsis–powdery mildew pathosystem. Proceedings of

the National Academy of Sciences of the United States of

America, 103, 17554–17559.

Fauteux F., Remus-Borel W., Menzies J.G., Belanger R.R.(2005) Silicon and plant disease resistance against

pathogenic fungi. FEMS Microbiology Letters, 249, 1–6.

Fawe A., Abou-Zaid M., Menzies J.G., Belanger R.R. (1998)

Silicon-mediated accumulation of flavonoid phytoalexins

in cucumber. Phytopathology, 88, 396–401.

Felton G.W., Duffey S.S. (1990) Inactivation of baculovirus

by quinones formed in insect-damaged plant tissues.Journal of Chemical Ecology, 16, 1221–1236.

Felton G.W., Eichenseer H. (1999) Herbivore saliva and its

effects on plant defence against herbivores and

pathogens. In Induced Plant Defenses Against Pathogens and

Herbivores: Biochemistry, Ecology, and Agriculture, pp. 19–36.

Eds A.A. Agrawal, S. Tuzin and E. Bent. St. Paul,

Minnesota: APS Press.Felton G.W., Summers C.B., Mueller A.J. (1994) Oxidative

responses in soybean foliage to herbivory by bean leaf

beetle and three-cornered alfalfa hopper. Journal of

Chemical Ecology, 20, 639–650.

Gatehouse J.A. (2002) Plant resistance towards insect

herbivores: a dynamic interaction. New Phytologist, 156,

145–169.Gomes F.B., Moraes J.C., Assis G.A. (2008a) Silicio e

imidacloprid na colonizacao de plantas por Myzus persicae

e no desenvolvimento veggetativo de batata inglesa.

Ciencia Rural, 38, 1209–1213.

Gomes F.B., Moraes J.C., Santos C.D., Antunes C.S. (2008b)

Uso de silıcico como indutor de resistencia em batata a

Myzus persicae (Sulzer) (Hemiptera : Aphididae).Neotropical Entomology, 37, 185–190.

Gomes F.B., Moraes J.C., Santos C.D., Goussain M.M.

(2005) Resistance induction in wheat plants by silicon

and aphids. Scientia Agricola, 62, 547–551.

Gong H., Zhu X., Chen K., Wang S., Zhang C. (2005) Silicon

alleviates oxidative damage of wheat plants in pots under

drought. Plant Science, 169, 313–321.Goussain M.M., Moraes J.C., Carvalho J.G., Nogueira N.L.,

Rossi M.L. (2002) Efeito da aplicacao de silicio em plantas

de milho no desenvolvimento biologico da

lagarta-do-cartucho Spodoptera frugiperda (J.E. Smith)

(Lepidoptera: Noctuidae). Neotropical Entomology, 31,

305–310.

Goussain M.M., Prado E., Moraes J.C. (2005) Effect ofsilicon applied to wheat plants on the biology and

probing behaviour of the greenbug Schizaphis graminum

(Rond.) (Hemiptera: Aphididae). Neotropical Entomology,

34, 807–813.

Goodman R.N., Kiraly Z., Wood K.R. (1986) Secondarymetabolite. In The Biochemistry and Physiology of Plant

Disease, pp 211–224. Ed. R.N. Goodman. Missouri:University of Missouri.

Guevel M.H., Menzies J.G., Belanger R.R. (2007) Effect ofroot and foliar applications of soluble silicon on powderymildew control and growth of wheat plants. EuropeanJournal of Plant Pathology, 119, 429–436.

Gupta S.C., Yazdani S.S., Hameed S.F., Agarwal M.L. (1992)Effect of potash application on incidence of Scirpophagaexcerptalis Walker in sugarcane. Journal of Insect Science, 5,97–98.

Gurr G.M., Kvedaras O.L. (2009) Synergizing biologicalcontrol: scope for sterile insect technique, induced plantdefences and cultural techniques to enhance naturalenemy impact. Biological Control,

DOI:10.1016/j.biocontrol.2009.02.013.Guslits I.S. (1990) Factors in the resistance of cereal crops to

Oulema melanopus and their role in reducing pestnumbers. Tezisy Dokladov VsesoyuznoiNauchno-Tekhnicheskoi Konferentsii ‘‘Problemy SelektsiiZernovykh Kul’tur Na Ustoichivost’ K Boleznyam I

Neblagopriyatnym Usloviyam Sredy’’, pp. 17–18, 12-14sentyabrya. Saratov, Moscow.

Hammerschmidt R. (2005) Silicon and plant defense: theevidence continues to mount. Physiological and MolecularPlant Pathology, 66, 117–118.

Hanifa A.M., Subramaniam T.R., Ponnaiya B.W.X. (1974)Role of silica in resistance to the leafroller, Cnaphalocrocismedinalis Guenee, in rice. Indian Journal of Experimental

Biology, 12, 463–465.Hanisch H.C. (1981) Die Populationsentwicklung von

Getreideblattlausen an Weizenpflanzen nach verschiedenhoher Stickstoffdungung und vorbeugender Applikationvon Kieselsaure zur Wirtspflanze. Mitteilungen der

Deutschen Gesellschaft fur Allgemeine und AngewandteEntomologie, 3, 308–311.

Horng S.B., Chu Y.I. (1990) Development and reproductionof Asian corn borer (Ostrinia furnacalis Guenee) fed onartificial diet containing silica. Chinese Journal ofEntomology, 10, 325–335.

Hunt J.W., Dean A.P., Webster R.E., Johnson G.N.,Ennos A.R. (2008) A novel mechanism by which silicadefends grasses against herbivory. Annals of Botany, 102,653–656.

International Rice Research Institute (IRRI) (1990) Program

report for 1989. Los Banos, Laguna, Philippines.Jat K.L., Pareek B.L. (2003) Biophysical and bio-chemical

factors of resistance in brinjal against Leucinodes orbonalis.Indian Journal of Entomology, 65, 252–258.

Jones L.H.P., Handreck K.A. (1967) Silica in soils, plantsand animals. Advances in Agronomy, 19, 107–149.

Kaufman P.B., Dayanandan P., Franklin C.I., Takeoka Y.(1985) Structure and function of silica bodies in theepidermal system of grass shoots. Annals of Botany, 55,487–507.



Keeping M.G., Kvedaras O.L. (2008) Silicon as a plant

defence against insect herbivory: response to Massey,

Ennos and Hartley. Journal of Animal Ecology, 77,

631–633.

Keeping M.G., Kvedaras O.L., Bruton A.G. (2009)

Epidermal silicon in sugarcane: cultivar differences and

role in resistance to sugarcane borer Eldana saccharina.

Environmental and Experimental Botany, 66, 54–60.

Keeping M.G., Meyer, J.H. (2002) Calcium silicate enhances

resistance of sugarcane to the African stalk borer Eldana

saccharina Walker (Lepidoptera: Pyralidae). Agricultural

and Forest Entomology, 4, 265–274.

Keeping M.G., Meyer J.H. (2006) Silicon-mediated

resistance of sugarcane to Eldana saccharina Walker

(Lepidoptera: Pyralidae): effects of silicon source and

cultivar. Journal of Applied Entomology, 130, 410–420.

Kennedy F.J., Nachiappan R. (1992) Certain Anatomical,

Physical and Chemical Basis for Differential Preference of Early

Shoot Borer (Chilo infuscatellus Snellen) in Sugarcane. In

Mededelingen van de Faculteit

Landbouwwetenschappen, Rijksuniversiteit Gent 57,

637–644.

Khan Z.R., James D.G., Midega C., Pickett J.A. (2008)

Chemical ecology ans conservation biological control.

Biological Control, 45, 210–224.

Korndorfer A.P., Cherry R., Nagata R. (2004) Effect of

calcium silicate on feeding and development of tropical

sod webworms (Lepidoptera: Pyralidae). Florida

Entomologist, 87, 393–395.

Kvedaras O.L., An M., Choi Y.S., Gurr G.M. (2009a) Silicon

enhances natural enemy attraction and biological control

through induced plant defences. Bulletin of Entomological

Research, DOI:10.1017/S0007485309990265.

Kvedaras O.L., Byrne M.J., Coombes N.E., Keeping M.G.

(2009b) Influence of plant silicon and sugarcane cultivar

on mandibular wear in the stalk borer Eldana saccharina.

Agricultural and Forest Entomology, (in press).

Kvedaras O.L., Gurr G.M., Choi Y-S. (2008) Silicon and

crop plants: induced plant defence and biological control.

In Abstracts of the IV Silicon in Agriculture Conference, Port

Edward, South Africa, October 2008, p. 38.

Kvedaras O.L., Keeping M.G. (2007) Silicon impedes stalk

penetration by the borer Eldana saccharina in sugarcane.

Entomologia Experimentalis et Applicata, 125, 103–110.

Kvedaras O.L., Keeping M.G., Goebel F.R., Byrne M.J.

(2007a) Water stress augments silicon-mediated

resistance of susceptible sugarcane cultivars to the stalk

borer Eldana saccharina (Lepidoptera: Pyralidae). Bulletin

of Entomological Research, 97, 175–183.

Kvedaras O.L., Keeping M.G., Goebel F.R., Byrne M.J.

(2007b) Larval performance of the pyralid borer Eldana

saccharina Walker and stalk damage in sugarcane:

influence of plant silicon, cultivar and feeding site.

International Journal of Pest Management, 53, 183–194.

Lakshmi K.V., Sudhakar T.R. (2003) Role of certain

chemical constituents on the development of cigarette

beetle, Lasioderma serricorne Fab. in turmeric. Indian

Journal of Plant Protection, 31, 122–124.

Lee K.P., Raubenheimer D., Behmer S.T., Simpson S.J.

(2003) A correlation between macronutrient balancing

and insect host-plant range: evidence from the specialist

caterpillar Spodoptera exempta (Walker). Journal of Insect

Physiology, 49, 1161–1171.

Lin T.F. (1993) Resistance to stem borer (Chilo suppressalis)

and the performance of agronomic characters of newly

developed indica rice lines. Bulletin of Taichung District

Agricultural Improvement Station, 40, 29–36.

Liu F., Song Y., Bao S., Lu H., Zhu S., Liang G. (2007)

Resistance to small brown planthopper and its

mechanism in rice varieties. Acta Phytophylacica Sinica, 34,

449–454.

Lord J.C. (2001) Desiccant dusts synergize the effect of

Beauveria bassiana (Hyphomycetes: Moniliales) on

stored-grain beetles. Journal of Economic Entomology, 94,

367–372.

Ma J.F. (2004) Role of silicon in enhancing the resistance of

plants to biotic and abiotic stresses. Soil Science and Plant

Nutrition, 50, 11–18.

Ma J.F., Miyake Y., Takahashi E. (2001) Silicon as a

beneficial element for crop plants. In Silicon in Agriculture,

pp 17–39. Eds L.E. Datnoff, G.H. Snyder,

G.H. Korndorfer. Amsterdam, The Netherlands: Elsevier

Science.

Ma J.F., Tamai K., Yamaji N., Mitani N., Konishi S.,

Katsuhara M., Ishiguro M., Murata Y., Yano M. (2006) A

silicon transporter in rice. Nature, 440, 688–691.

Massey F.P., Ennos A.R., Hartley S.E. (2006) Silica in

grasses as a defence against insect herbivores: contrasting

effects on folivores and a phloem feeder. Journal of Animal

Ecology, 75, 595–603.

Massey F.P., Ennos A.R., Hartley, S.E. (2007) Herbivore

specific induction of silica-based plant defences. Oecologia,

152, 677–683.

Massey F.P., Hartley S.E. (2009) Physical defences wear you

down: progressive and irreversible impacts of silica on

insect herbivores. Journal of Animal Ecology, 78, 281–291.

Matichenkov V.V., Calvert D.V., Snyder G.H. (2000)

Prospective of silicon fertilization for citrus in Florida.

Proceedings of the Soil and Crop Science Society of Florida, 59,

137–141.

Matlou M.C. (2006) A comparison of soil and foliar-applied

silicon on nutrient availability and plant growth and

soil-applied silicon on phosphorus availability.

Unpublished M.Sc Thesis. University of KwaZulu-Natal,

Pietermaritzburg, South Africa.

McColloch J.W., Salmon S.C. (1923) The resistance of

wheat to the hessian fly–a progress report. Journal of

Economic Entomology, 16, 293–298.



Mebrahtu T., Kenworthy W.J., Elden T.C. (1988) Inorganic

nutrient analysis of leaf tissue from soybean lines

screened for Mexican bean beetle resistance. Journal of

Entomological Science, 23, 44–51.

Menzies J., Bowen P., Ehret D. (1992) Foliar applications of

potassium silicate reduce severity of powdery mildrew on

cucumber, muskmelon, and zucchini squash. American

Society for Horticultural Science, 117, 902–905.

Meyer J.H., Keeping M.G. (2005) Impact of silicon in

alleviating biotic stress in sugarcane in South Africa.

Sugarcane International, 23, 14–18.

Miller B.S., Robinson R.J., Johnson J.A., Jones E.T.,

Ponnaiya B.W.X. (1960) Studies on the relation between

silica in wheat plants and resistance to Hessian fly.

Journal of Economic Entomology, 53, 995–999.

Mishra B.K., Sontakke B.K., Mohapatra H. (1990)

Antibiosis mechanisms of resistance in rice varieties to

yellow stem borer Scirpophaga incertulas Walker. Indian

Journal of Plant Protection, 18, 81–83.

Mishra N.C., Misra B.C. (1992) Role of silica in resistance of

rice, Oryza sativa L. to white-backed planthopper, Sogatella

furcifera (Horvath) (Homoptera: Delphacidae). Indian

Journal of Entomology, 54, 190–195.

Mishra N.C., Misra B.C. (1993) Role of plant chemicals

determining resistance in rice to white-backed

planthopper Sogatella furcifera. Environment and Ecology,

11, 88–91.

Moore D. (1984) The role of silica in protecting Italian

ryegrass (Lolium multiflorum) from attack by dipterous

stem-boring larvae (Oscinella frit and other related

species). Annals of Applied Biology, 104, 161–166.

Moraes J.C., Carvalho S.P. (2002) Resistance induction on

sorghum plants Sorghum bicolor (L.) Moench. to the

greenbug Schizaphis graminum (Rond., 1852) (Hemiptera:

Aphididae) by silica application. Ciencia e Agrotecnologia,

26, 1185–1189.

Moraes J.C., Goussain M.M., Basagli M.A.B., Carvalho G.A.,

Ecole C.C., Sampaio M.V. (2004) Silicon influence on the

tritrophic interaction: Wheat plants, the greenbug

Schizaphis graminum (Rondani) (Hemiptera: Aphididae),

and its natural enemies, Chrysoperla externa (Hagen)

(Neuroptera: Chrysopidae) and Aphidius colemani Viereck

(Hymenoptera: Aphidiidae). Neotropical Entomology, 33,

619–624.

Moraes J.C., Goussain M.M., Carvalho G.A., Costa R.R.

(2005) Feeding non-preference of the corn leaf aphid

Rhopalosiphum maidis (Fitch, 1856) (Hemiptera:

Aphididae) to corn plants (Zea mays L.) treated with

silicon. Ciencia e Agrotecnologia, 29, 761–766.

Nakano K., Abe G., Taketa N., Hirano C. (1961) Silicon as

an insect resistant component of host plant, found in the

relation between the rice stem-borer and rice plant.

Japanese Journal of Applied Entomology and Zoology, 5,

17–27.

Nakata Y., Ueno M., Kihara J., Ichii M., Taketa S., Arase S.

(2008) Rice blast disease and susceptibility to pests in asilicon uptake-deficient mutant lsi1 of rice. Crop Protection,

27, 865–868.

Narwal R.P. (1973) Silica bodies and resistance to infection

in jowar (Sorghum vulgare Perc.). Agra University Journal of

Research (Science), 22, 17–20.

Neri D.K., Moraes J.C., Gavino M.A. (2005) Interacao silıcio

com inseticida regulador de crescimento no manejo dalagarta - do - cartucho Spodoptera frugiperda (J. E. Smith,

1797) (Lepidoptera: Noctuidae) em milho. Cienciae

Agrotecnologia, 29, 1167–1174.

O’Reagain P.J., Mentis M.T. (1989) Leaf silification in

grasses–a review. Journal of the Grassland Society of

Southern Africa, 6, 37–43.

Pan Y.C., Eow K.L., Ling S.H. (1979) The effect of bagassefurnace ash on the growth of plant cane. Sugar Journal,

42, 14–16.

Panda N., Kush G.S. (1995) Host Plant Resistance to Insects.

Wallingford, UK: CAB International.

Parrella M.P., Costamagna T.P., Kaspi R. (2007) The

addition of potassium silicate to the fertilizer mix to

suppress Liriomyza leafminers attacking chrysanthemums.Acta Horticulturae, 747, 365–369.

Peterson S.S., Scriber J.M., Coor J.G. (1988) Silica, cellulose

and their interactive effects on the feeding performance

of the southern armyworm Spodoptera eridania (Cramer)

(Lepidoptera: Noctuidae). Journal of the Kansas

Entomological Society, 61, 169–177.

Ponnaiya B.W.X. (1951) Studies on the genus Sorghum. II.The cause of resistance in sorghum to the insect pest

Atherigona indica M. Madras University Journal, 21,

203–217.

Ramachandran R., Khan Z.R. (1991) Mechanisms of

resistance in wild rice Oryza brachyantha to rice leaffolder

Cnaphalocrocis medinalis (Guenee) (Lepidoptera:

Pyralidae). Journal of Chemical Ecology, 17, 41–65.Ranganathan S., Suvarchala V., Rajesh Y.B.R.D.,

Prasad M.S., Padmakumari A.P., Voleti S.R. (2006)

Effects of silicon sources on its deposition, chlorophyll

content, and disease and pest resistance in rice. Biologia

Plantarum, 50, 713–716.

Rao S.D.V. (1967) Hardness of sugarcane varieties in

relation to shoot borer infestation. Andhra Agricultural

Journal, 14, 99–105.

Rao C.N., Panwar V.P. (2001) Anatomical plant factors

affecting resistance to Atherigona spp. in maize. Annals of

Agricultural Research, 22, 165–168.

Redmond C.T., Potter D.A. (2007) Silicon fertilization does

not enhance creeping bentgrass resistance to cutworms

and white grubs. USGA Turfgrass and Environmental

Research [Online], 6, 1–7.

Rupali G., Jyoti R., Chavan J.K. (2003) Biochemical analysis

of chickpea cultivars in relation to pod borer infestation.

Indian Journal of Agricultural Biochemistry, 16, 47–48.



Rutherford R.S., Meyer J.H., Smith G.S., Van Staden J.(1993) Resistance to Eldana saccharina (Lepidoptera:Pyralidae) in sugarcane and some phytochemicalcorrelations. Proceedings of the South African SugarTechnologists Association, 67, 82–87.

Saeb H., Ganbalani G.N., Rajabi G. (2002) Comparison ofthe resistance of some rice genotypes of Gilan province tothe striped stem borer, Chilo suppressalis (Walker) andinvestigating the role of silica in resistance. Journal ofAgricultural Sciences: Islamic Azad University, 7, 17–25.

Saigusa M., Onozawa K., Watanabe H., Shibuya K. (1999)Effects of porous hydrate calcium silicate on the wearresistance, insect resistance and disease tolerance of turfgrass ‘‘Miyako’’. Grassland Science, 45, 416–420.

Salim M., Saxena R.C. (1992) Iron, silica, and aluminiumstresses and varietal resistance in rice: effects onwhitebacked planthopper. Crop Science, 32, 212–219.

Sasamoto K. (1953) Studies on the relation between insectpests and silica content in rice plant (II). On the injury ofthe second generation larvae of rice stem borer. OyoKontyu, 9, 108–110.

Sasamoto K. (1955) Studies on the relation between insectpests and silica content in rice plant (III). On the relationbetween some physical properties of silicified rice plantand injuries by rice stem borer, rice plant skipper and ricestem maggot. Oyo Kontyu, 11, 66–69.

Sasamoto K. (1958) Studies on the relation between silicacontent of the rice plant and insect pests. IV. On theinjury of silicated rice plant caused by the rice-stem-borerand its feeding behaviour. Japanese Journal of AppliedEntomology and Zoology, 2, 88–92.

Savant N.K., Korndorfer G.H., Datnoff L.E., Snyder, G.H.(1999) Silicon nutrition and sugarcane production: areview. Journal of Plant Nutrition, 22, 1853–1903.

Savant N.K., Snyder G.H., Datnoff L.E. (1997) Siliconmanagement and sustainable rice production. Advances inAgronomy, 58, 151–199.

Sekhon S.S., Kanta U. (1997) Mechanisms and bases ofresistance in maize to spotted stem borer. In Proceedings ofthe International Symposium on Insect Resistant Maize: RecentAdvances and Utilization, pp. 106–111, Mexico.

Setamou M., Schulthess F., Bosque-PerezN.A., Thomas-Odjo A. (1993) Effect of plant nitrogenand silica on the bionomics of Sesamia calamistis(Lepidoptera: Noctuidae). Bulletin of EntomologicalResearch, 83, 405–411.

Sinel’nikov E.A., Shapiro I.D. (1990) Deposition of silicondioxide as a factor in the resistance of barley to Oscinellapusilla. Tezisy Dokladov Vsesoyuznoi Nauchno-TekhnicheskoiKonferentsii ‘‘Problemy Selektsii Zernovykh Kul’tur NaUstoichivost’ k Boleznyam i Neblagopriyatnym UsloviyamSredy’’, pp. 126–127, 12-14 sentyabrya. Saratov,Moscow.

Singh R., Agarwal R.A. (1988) Role of chemicalcomponents of resistant and susceptible genotypes ofcotton and okra in ovipositional preference of cottonleafhopper. Proceedings of the Indian Academy of Sciences:Animal Sciences, 97, 545–550.

Singh B., Yazdani S.S., Singh R. (1993) Relationshipbetween biochemical constituents of sweet potatocultivars and resistance to weevil (Cylas formicarius Fab.)damage. Journal of Entomological Research, 17,283–288.

Smith C.M. (1997) An overview of the mechanisms andbases of insect resistance in maize. In Proceedings of the

International Symposium on Insect Resistant Maize: Recent

Advances and Utilization, pp. 1–12, Mexico.Smith M.T., Kvedaras O.L., Keeping M.G. (2007) A novel

method to determine larval mandibular wear of theAfrican stalk borer, Eldana saccharina Walker(Lepidoptera: Pyralidae). African Entomology, 15, 204–208.

Soliman A.M., El-Atta W.M., Elela R.G., Abdel-Wahab A.E.(1997) Effect of certain chemical components and sourceof rice plant on its resistance to rice stem borer, Chilo

agamemnon Bles. and rice leaf miner, Hydrellia prosternalis

Deem. Egyptian Journal of Agricultural Research, 75,667–680.

Stout M.J., Workman J., Duffey S.S. (1994) Differentialinduction of tomato foliar proteins by arthropodherbivores. Journal of Chemical Ecology, 20, 2575–2594.

Subbarao D.V., Perraju A. (1976) Resistance in some ricestrains to first-instar larvae of Tryporyza incertulas (Walker)in relation to plant nutrients and anatomical structure ofthe plants. International Rice Research Newsletter, 1,14–15.

Sudhakar G.K., Singh R., Mishra S.B. (1991) Susceptibilityof rice varieties of different durations to rice leaf folder,Cnaphalocrocis medinalis Guen. evaluated under variedland situations. Journal of Entomological Research, 15,79–87.

Sujatha G., Reddy G.P., Murthy M.M. (1987) Effect ofcertain biochemical factors on the expression of resistanceof rice varieties to brown planthopper (Nilaparvata lugens

Stal). Journal of Research APAU, 15, 124–128.Sunio L.M., Caldo R., Cohen M.B. (2000) Field screening of

stem borer resistance in new plant type lines. International

Rice Research Notes, 25, 25–27.Taneja A.D., Sharma J.C., Singh D.P., Sharma A.P.,

Kairon M.S. (1988) Biochemical changes in Gossypium

hirsutum cotton in relation to attack by jassid (Empoasca

spp.). ISCI Journal: Indian Society for Cotton Improvement, 13,33–36.

Thaler J.S., Fidantsef A.L., Bostock R.M. (2002) Antagonismbetween jasmonate- and salicylate-mediated inducedplant resistance: effects of concentration and timing ofelicitation on defense-related proteins, herbivore, andpathogen performance in tomato. Journal of Chemical

Ecology, 28, 1131–1159.

Tomquelski G.V., Martins G.L., Papa G. (2007) Effect ofresistance inductors acibenzolar-S-methyl and silicon inthe biology of Alabama argillacea (Lepid.: Noctuidae) oncrop cotton. Revista de Agricultura (Piracicaba), 82,170–175.



Voleti S.R., Padmakumari A.P., Raju V.S., Babu S.M.,Subramania R. (2008) Effect of silicon solubilizers onsilica transportation, induced pest and disease resistancein rice (Oryza sativa L.). Crop Protection, 27, 1398–1402.

Wiese J., Wiese H., Schwartz J., Schubert S. (2005) Osmoticstress and silicon act additively in enhancing pathogenresistance in barley against barley powdery mildew.Journal of Plant Nutrition and Soil Science, 168, 269–274.

Yoshihara T., Sogawa K. (1979) Soluble silicic acid andinsoluble silica contents in leaf sheaths of rice varieties

carrying different BPH-resistance genes. International Rice

Research Newsletter, 4, 12–13.

Zadda K., Ragjendran R., Vijayaraghavan C. (2007) Inducedsystemic resistance to major insect pests of brinjal throughorganic farming. Crop Research (Hisar), 34, 125–129.

Zouhourian-Saghiri L., Kobilinsky A., Gillon Y.,Gagnepain C. (1983) Lois d’usure mandibulaire chezLocusta migratoria (Orthopt. Acrididae) son utilisationpour la datation des ailes. Annals of the Entomological

Society of France, 19, 335–352.


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