Biological Control 32 (2005) 461–472

www.elsevier.com/locate/ybcon

EVect of microclimate heterogeneity and ventilation system on entomopathogenic hyphomycete infection of Trialeurodes vaporariorum (Homoptera: Aleyrodidae) in Mediterranean

greenhouse tomato

J. Farguesa,¤, N. Smitsa, M. Rougiera, T. Boulardb, G. Ridrayc, J. Lagierc,B. Jeannequinc, H. Fatnassib, M. Mermierb

a Centre de Biologie et de Gestion des Populations (CBGP), INRA, Campus International de Baillarguet, CS 30 016, 34988 Montferrier-sur-Lez, Cedex, France

b Unité Systèmes de Cultures Maraîchers sous Abris (SCMSA), INRA, Domaine de Saint-Paul, Site Agroparc, 84914 Avignon Cedex 9, Francec Systèmes Agraires et Développement, INRA, Domaine Expérimental Horticole du Mas Blanc, 66200 Alenya, France

Received 13 October 2004; accepted 17 December 2004

Abstract

Collaborative research was conducted in the south of France to assess constraints related to both climate heterogeneity and ven-tilation systems on the control potential of a Lecanicillium muscarium-based formulation against whiteXies in Mediterranean green-houses. Four series of small-scale greenhouse trials were performed in 2001 and 2002. Two applications at 4–5 day intervals ofMycotal were conducted on young larvae of the greenhouse whiteXy, Trialeurodes vaporariorum, at the rate recommended by themanufacturer (ca. 1010 viable spores per liter of water suspension). The climatic heterogeneity was taken into account by comparingthe fungus-induced mortality of nymphs located on lateral row plants to that of nymphs on center row plants. In spite of signiWcantdiVerences in air Xows (0.7–1.2 and 0.3 ms¡1, respectively) there was no eVect on fungus eYcacy (53–76% mortality). When compar-ing the inXuence of greenhouse equipment (sophisticated glasshouse vs. polyethylene-covered greenhouse), the fungus was notaVected (89–96% mortality) in spite of signiWcant diVerences in ventilation rates. The results conWrmed that entomopathogenicHyphomycetes have a strong potential for microbial control of whiteXy larvae infesting tomato crops at moderate ambient humidityin Mediterranean greenhouses in spite of windy periods. These investigations conWrmed that microclimatic conditions prevailing inthe targeted insect habitat (under-leaf surface boundary layer) are greatly disconnected from that of both outside and inside thegreenhouse. In northern Mediterranean greenhouses, non-stressed tomato crops provide unexpected favorable conditions formycoinsecticide use against a phyllophagous insect. 2004 Elsevier Inc. All rights reserved.

Keywords: Microbial control; Entomopathogenic Hyphomycetes; Trialeurodes vaporariorum; Lecanicillium muscarium; Northern Mediterraneanarea; Tomato greenhouse; Climatic constraints

1. Introduction

In spite of the recent emergence of begomovirus epi-demics caused by the extension of the distribution area

¤ Corresponding author. Fax: +33 4 99 62 33 45.E-mail address: fargues@ensam.inra.fr (J. Fargues).

1049-9644/$ - see front matter 2004 Elsevier Inc. All rights reserved.doi:10.1016/j.biocontrol.2004.12.008

of the whiteXy Bemisia tabaci Genadius in Mediterra-nean countries, Trialeurodes vaporariorum Westwoodstill remains the major insect pest of greenhouse tomatocrops in Europe (van Lenteren and Noldus, 1990).Negative impact of insecticide resistance of this whiteXyin integrated pest management has encouraged thedevelopment of alternative methods of control.

462 J. Fargues et al. / Biological Control 32 (2005) 461–472

Entomopathogenic Hyphomycetes show promise forwhiteXy control, because only they are capable of infect-ing plant-sucking insects by penetrating through thecuticle (Fransen, 1990). Various isolates of Beauveriabassiana (Balsamo) Vuillemin, Paecilomyces fumosoro-seus (Wize) Brown and Smith, and Lecanicillium musca-rium Zare and Gams, have been selected for theirpotential as mycoinsecticides for whiteXy control (Bol-ckmans et al., 1995; Ekbom, 1979; Faria and Wraight,2001; Hall, 1985; Osborne and Landa, 1992; Ravensberget al., 1990; Smith, 1993; Wraight et al., 1994, 1998;Wright, 1992, 1995), but most of them required highhumidity conditions for infection (Ekbom, 1981; Helyeret al., 1992; Lacey et al., 1996).

More recently, Fargues et al. (2003) investigated cli-matic constraints for mycoinsecticides against whiteXiesin Mediterranean tomato glasshouses. It was found thatchanges in ambient humidity realized through glass-house climate control did not aVect whiteXy infection byfungi. These unexpected results were explained by theconditions prevailing in the habitat of whiteXy larvae onthe under-leaf surface boundary layer as demonstratedby Boulard et al. (2002).

Therefore, the present study was initiated to evaluatethe eVect of the greenhouse microclimatic heterogeneitydue to the position of tomato plants relative to ventopenings, and that of ventilation systems, on fungalinfection for control of T. vaporariorum on tomato(Solanum esculentum Miller). It focuses on improvingthe understanding of the climatic constraints formycoinsecticide eYcacy in northern Mediterraneangreenhouses.

2. Materials and methods

2.1. Fungal origin and viability tests

The L. muscarium-based product, Mycotal (van derPas et al., 1996) used in these studies, was provided byKoppert B.V. (Berkel en Rodenrijs, The Netherlands).Mycotal is based on conidia of the KV01 strain of L.muscarium isolated from a dead T. vaporariorum adultfrom a glasshouse in the UK (R.A. Hall, personal com-munication). In 2001 and 2002, greenhouse assays wereconducted with Mycotal as a wettable powder with alabel claim of 1010 viable conidia gram¡1 used in combi-nation with 0.25% emulsiWable oil with spreaders (Kop-pert oil formulation as KOF).

Conidial viability for samples of the L. muscarium-based Mycotal was checked regularly during the experi-mental series by estimating the density of colonyforming units (CFU) (Fargues et al., 2003). Viability ofMycotal inocula over the course of the experiments werethen estimated at ca. 3.4 (3.2–3.6) £ 109 mL¡1 in 2001,and at ca. 3.7 (3.6–3.8) £ 109 mL¡1 in 2002.

2.2. Greenhouse experiments

Four experiments were conducted on tomato plantsin greenhouses over 2 years at the INRA ExperimentalResearch Unit located in Alenya (42°38�N latitude,2°58�E longitude and 5 m altitude) in the south ofFrance. Greenhouses were oriented North East–SouthWest (315°). The dominant winds consisted of a North-Westerly wind, called “Tramontane,” an Easterly windcalled “Levant,” and a South-Westerly wind called“Marinade.”

Two experiments (Experiments 1 and 2) were carriedout in 2001 in a commercial plastic cold greenhouse (ogi-val tunnel of 324 m2, 40.5 m length, 8 m width, and 4 mhigh). It was planted in a sandy loam soil with tomatocultivar Brenda (Gautier SA, Eyragues, France).Tomato plants (2- to 3-leaf stage) were transplanted onApril 5, 2001 in two single rows at two sides and threedouble rows in the center of the tunnel. Plants werespaced 90 cm apart between rows and 53 cm apart withinrows. Experiments were performed between May 21 andJune 19 (Experiment 1), and June 28 and July 18 (Exper-iment 2).

Two other experiments were conducted in 2002 in twoplastic-covered tunnels (Experiments 3 and 4), and in aheated double span glasshouse with polycarbonatesheets (Experiment 3, only). The structure of both tun-nels was identical to that of the tunnel used in 2001, andthe cultural design was similar, except that the cultivarused was Gardel (SVS Holland BV, Enkhuizen, TheNetherlands). Tomato plants were transplanted onMarch 26, 2002. The commercial soilless glasshouse of409 m2 (32 m length, 12.8 m width, and 4 m high) wasplanted with the tomato cultivar Mariachi (Rijk ZwaanZaadteelt en Zaadhandel BV, De Lier, The Netherland)on February 11, 2002. Tomato plants were grown undercommercial conditions on pozzolan–turf slabs in twosingle rows at two sides and two double rows in the cen-ter of the glasshouse. Plants were spaced 60 cm apartbetween rows and 40 cm apart within rows. Experimentswere performed between May 17 and June 10 (Experi-ment 3), and July 1 and 24 (Experiment 4).

Crop protection consisted of controlling Botrytisdevelopment on stem wounds by using single-handedpruning shears (Felco F-19 bypass pruner with a spraydevice, Felco SA, Les Geneveys-sur-CoVrane, Switzer-land) for applying an experimental formulation of thefungal antagonist Ulocladium atrum on the cuttingwounds (Fruit and Nicot, 1999). There was no pesticidetreatment during each of the four experiments reportedin 2001 and 2002.

Harvest started on 20 May in 2001 and Wnished onthe second week of July, but the crop was maintaineduntil the end of July to allow data recording on fungus-treated T. vaporariorum populations. A similar harvest-ing program was conducted in 2002.

J. Fargues et al. / Biological Control 32 (2005) 461–472 463

2.3. Experimental design

A factorial design was used to compare the eVects ofthe greenhouse climate heterogeneity on fungus-inducedmortality of T. vaporariorum nymphs. In 2001, investiga-tions of the climate heterogeneity compared conditionsprevailing in tomato plants in the central row vs. that ofplants in the wind-exposed lateral row, and for these lastones, the conditions in windward plants vs. those in lee-ward plants. The experiment was repeated twice overtime in 2001. Each row was divided into equal blocks ofat least eight tomato plants (single rows) or eight couplesof plants (double rows) to take into account the North–South climatic heterogeneity inside the tunnel. Therewere two guard plants on each row between the blocks.Because of the immobility of whiteXy larvae, tomatoplants could be considered as units for the mycoinsecti-cide treatments. Treatments consisted of one mycoinsec-ticide, Mycotal, and controls (water). The Easternborder row was divided into Wve blocks in front of eachof Wve lateral vent openings. In each of these blocks, thefour tomato plants facing the border vent were treatedwith the fungus preparation and two proximate plantswere used as controls. To avoid undesirable projectionof fungal inoculum, each selected tomato plant was iso-lated during spraying by using a plastic Wlm. The fourtreated tomato plants consisted of two windwardlocated plants, on the right of the border vent, and twoleeward plants on their left. The central row was dividedin Wve blocks between the top vent openings. In the cen-ter of each pseudo-parcel, two plants were selected ran-domly as controls and for fungus treatments. Two leaveswere used for artiWcial infestations and subsequent sam-plings, except in the second experiment, where data wererecorded on one leaf per plant only in the central rowplants devoted to controls.

In 2002, investigations were focused on the eVect ofmicroclimate variability caused by ventilation systems.The experimental design was based on a comparisonbetween a “conventional ( D traditional) tunnel” and a“highly ventilated tunnel.” In the Wrst experiment, thecomparison was extended to a third structure that con-sisted of a heated glasshouse. To avoid the greenhouseclimatic heterogeneity studied in 2001, assays were con-ducted on plants selected in four blocks of each of thetwo central double rows of the glasshouse. The two cen-tral double rows on both sides of the double row locatedin the middle of the tunnels were used. These blocks werelocated between the Wve top vent openings. The sampleunit consisted of one artiWcially infested young leaf(third node from the growing tip) per selected plant. Theprocedures were identical for the two experimental seriesconducted in 2001. To prevent possible contamination,spraying was applied on pairs of plants in the doublerow, face to face along the row, and pairs of treatedplants were separated by one pair of untreated plants.

2.4. Climate control strategies

The environment in each cropping structure was reg-ulated separately. In 2001, the experimental tunnel was“classically” ventilated by means of side openings. In2002, experiments were conducted under three diVerentconditions. One tunnel, identical to that used in 2001,was only ventilated by means of side openings providingvent opening surfaces ranging from 0 to 7% with respectto the covered area. A second tunnel was “highly venti-lated” by additional gable end openings and perforatedWlm sheets for the windward gable. The ventilation open-ing/soil surface was then Wxed at 17.7%. The climate ofthe glasshouse used in spring 2002 (Experiment 3) wascontrolled using an automatic piloting system, Syspil(Gervais et al., 1996). Its vent surface openings rangedfrom 0 to 18.5%.

2.5. Microclimatic investigations

Outside weather measurements were obtained from aweather station at 50-m distance from the greenhouses.They consisted of radiation, air temperature and humid-ity, wind speed and direction, respectively. In the centerof each greenhouse (at an equal distance from the sidesand from the gable ends), at a height of 1.8 m a pyra-nometer and a ventilated thermo-hygrometer (HMP45C) were installed. To characterize the conditions pre-vailing in the tomato-canopy air and to evaluate the spa-tial heterogeneity of the greenhouse microclimate,capacitive Vaisala probes (HMP 45C), and air velocitytransducers (omni directional model; TSI France,Europarc, Marseille, France) were positioned in the can-opy at the height of the infested leaves, ranging from 1.3to 1.7 m, according to the tomato crop growth. Micro-meteorological measurements were performed every 15 sand averaged each 15 min by using Campbell 23 X dataloggers (Campbell ScientiWc, Shepshed, Leicestershire,LE 129RP, UK). Microclimatic changes due to canopytranspiration near the under-leaf surface were estimatedusing thin thermocouples (Type T, Engelhard Pyro-Con-trôle, Vaulx-en-Velin, France) attached under the leavesin the middle vein to measure leaf temperature and smallthermo-hygrometers (IN Intertechnique, Plaisir, France)placed at 5 mm from the leaf surface to measure air tem-perature and humidity. The details of this study and itstheoretical and experimental implication can be found inpublications specially devoted to the boundary layer cli-mate (Boulard et al., 2002, 2004).

2.6. Insect culture and plant infestation

WhiteXies were mass-reared in screened cages(50 £ 50 £ 50 cm) containing young green beans plants(Phaseolus vulgaris L., cv. Contender, Oxadis, La Ver-pillière, France) at a daily temperature of 22 § 1 °C and

464 J. Fargues et al. / Biological Control 32 (2005) 461–472

nightly temperature of 18 § 1 °C and a photoperiod of16:8 (L:D). To prevent a possible decreasing of fecunditydue to host plant change (van Lenteren et al., 1996),insects were reared for at least two generations ontomato plants before artiWcial infestation.

For heavy and homogeneous larval population levels,artiWcial infestations were carried out on randomlyselected plants on May 2, and June 15, in 2001, and onApril 29 and June 17, in 2002. The greenhouses were pre-viously treated 8 days before artiWcial infestations withpyriproxyfen (juvenile hormone mimics) and methomyl(oxime carbamate insecticide) to kill indigenous white-Xies. ArtiWcial infestation consisted of introducing 80young adults of whiteXy (sex-ratio t 1:1) inside anorgandy sleeve (300-�m mesh), installed around oneyoung selected leaf of the previously selected plants.WhiteXy adults were given the opportunity to lay eggsfor 3–4 days, resulting in at least 100 eggs/leaf. Within 2–3 weeks, depending on climatic conditions, the targetedwhiteXy populations consisted of mostly young second-instar nymphs.

2.7. Treatment and sample examination procedures

Mycotal was used under the conditions recommendedby the manufacturer, at a rate of 1 g of wettable powderper liter of water with 0.25% emulsiWable oil with spread-ers in 2001 and 2002. All applications were made using asingle-nozzle, atomizing (air-assist), 15-L backpacksprayer (Berthoud-Exel GSA, Villefranche-sur-Saône,France), operating at a pressure of 4 bars delivering0.65 L/min. During spraying, the spray nozzle wasdirected at a right angle to the under leaf surface of eachtreated plant, making sure the undersides of leaves werecoated. The amount of water was estimated at 2000 L/hectare. The control plants were sprayed with water,

according to the results of previous assays showing noeVect of formulation ingredients in greenhouse trials(Fargues et al., 2003). Treatments consisted of two suc-cessive applications at 4–5 day intervals, on May 21–25and June 29–July 4, in 2001; and on May 17–21, and July1–5, in 2002. To optimize the fungal inoculum potential,spraying was always done at the end of the day at16:00 h on cloudy and rainy days, and at 17:00 h onsunny days.

Because second-, third-, and fourth-instar larvae aresessile and attached to the leaf surface, mortality assess-ments were done at the end of the trials, when more than80% of whiteXy adults had emerged in the controls(about 3 weeks after the Wrst fungal application). Sam-ples consisting of infested nymphs were collected, trans-ferred to the laboratory for counting emerged whiteXies( D empty pupal cases), surviving nymphs, parasitizednymphs (appearance of hymenopteriform larvaethrough the transparent whiteXy skin or empty pupalcase with typical hole of parasitoid emergence), nymphsconsumed by predatory bugs (collapsed cuticle), andfungus-killed nymphs (color change), by using a stereo-microscope at 36£ magniWcation. To avoid errors due todouble counting, each observed nymph was marked witha permanent ink pen. The developmental stage of eachcadaver was also noted.

2.8. Statistical analysis

Because of the expected eVect of the microclimaticconditions that varied according to the outside weather,each replicate was considered as an entity. The samplingunit was the collected leaf. The total number of live anddead insects harvested from each leaf was used for dataanalysis. When the time of death provided useful infor-mation, mortality data were computed as mortality

Table 1Climatic conditions prevailing inside a tomato greenhouse related to the plant row location in Experiments 1 and 2

Averaged data (§SD).a Climate measurements performed outside at 5 m high and 50 m from the greenhouses(x) and inside the greenhouse at two canopy locations(y).b Thin thermocouples pricked in the middle vein on the under-leaf surface(y).

Experiment 1 (May 21–June 5, 2001) Experiment 2 (June 29–July 18, 2001)

Outsidex Eastern border rowy Central rowy Outsidex Eastern border rowy Central rowy

Air speed (m s¡1)a

Daytime (8:00–20:00 h) 2.08 § 0.09 0.40 § 0.26 0.11 § 0.06 2.11 § 1.28 0.53 § 0.29 0.14 § 0.06Nighttime (20:00–8:00 h) 1.99 § 0.10 0.12 § 0.09 0.06 § 0.06 1.18 § 0.75 0.11 § 0.07 0.05 § 0.03

Air temperature (°C)a

Daytime 27.1 § 4.0 26.5 § 3.4 27.4 § 3.4 26.1 § 3.6 27.3 § 3.1 29.0 § 3.7Nighttime 18.7 § 2.9 19.7 § 3.4 19.9 § 2.8 20.8 § 2.9 21.3 § 3.1 21.4 § 3.1

Leaf surface temperature b

Daytime 24.6 § 3.0 24.8 § 3.2 26.5 § 2.8 26.2 § 3.2Nighttime 18.2 § 3.0 18.2 § 3.1 20.1 § 3.1 19.8 § 3.1

Air humidity (RH%)a

Daytime 54.1 § 13.1 61.1 § 10.3 67.7 § 9.2 53.5 § 17.6 60.8 § 14.4 64.2 § 11.8Nighttime 70.1 § 11.5 79.1 § 11.1 82.9 § 9.2 68.4 § 15.3 78.8 § 11.9 82.2 § 10.8

J. Fargues et al. / Biological Control 32 (2005) 461–472 465

occurring in “young instars“ (i.e., occurring in secondinstar) and in “all instars“ (i.e., occurring from second tofourth instar combined). Population density data werelog (x + 1)-transformed and mortality data were arcsine

Fig. 1. Variation of ambient humidity and outside temperature in twocanopy locations: center row plants and Eastern row plants during thecritical periods of time for fungus infection of T. vaporariorum larvaein Experiments 1 and 2 (May 21–28, and from June 28 to July 6, 2001,respectively).

square-root-transformed. The eVect of fungal treatmentand climatic conditions on larval mortality was analyzedusing one- and two-way analyses of variance (ANOVA)(�D 0.05), followed by comparison of means using theStudent–Newman–Keuls (SNK) multiple range test. Sta-tistical analyses were performed using SigmaStat (SPSS,1997). Means of transformed data were included in bothtext and tables as means § SEM.

3. Results

3.1. Physical environment

In 2001 (Experiments 1 and 2), the weather was gener-ally sunny and normally dry for the region during bothexperiment periods (Table 1, Fig. 1). On sunny days(900Wm¡2), maximum solar radiation inside the glass-house compartments reached 700Wm¡2 during the Wrstexperiment and 550–600 Wm¡2 during the second one,due to the application of white paint to increase shading.Previous air speed measurements performed inside tunnelsduring peaks (at 6.07§0.82ms¡1) of the North-Westerlywind (327§19°) showed signiWcant diVerences of airXowsinside the border row according to the orientation ofplants related to the dominant wind. AirXows at 1.20 mreached 1.13§0.21ms¡1 in the canopy of the windwardlocated plants, instead of 0.46§0.09ms¡1 in that of theleeward plants. These diVerences were taken into accountfor the protocol design of experiments carried out in 2001,but the winds changed frequently in both direction andspeed over the periods of experimentation (Fig. 2).

During the Wrst experiment, maximal temperaturesmeasured inside greenhouse were from 1 to 5 °C higherthan outside ones, and minimal temperatures from 0 to3 °C less than outside (Table 1, Fig. 1). Inside air humidity

Fig. 2. Variation of outside wind direction and speed, of air Xows in the tomato canopy related to the location of plants in the center of the green-house and in the Eastern border, during the critical periods of time for fungus infection of T. vaporariorum larvae in Experiment 1 (May 21–29, 2001).

466 J. Fargues et al. / Biological Control 32 (2005) 461–472

was higher than outside (Table 1, Fig. 1). Diurnal windspeed was ca. 2.1 m s¡1 over the period (mainly due toboth Easterly and South-Easterly winds from 90 to 170°),except peaks at 4–5 m s¡1 of the North-Westerly wind(from 310 to 350°) on May 24–26, 31, and June 1–3. Therewas a humidity diVerential in both diurnal minima (6.6points of RH between averaged data) and nocturnal max-ima (3.8 points) related to the location inside the tunnel,with an increase of the air humidity recorded in the cen-tral rows compared to that of the Eastern border (Table 1,Fig. 1). AirXows ranged from 0.0 to 0.3 m s¡1 in the centralrows and from 0.1 to 0.8 m s¡1 in the border row, depend-ing on the outside wind speed (Table 1, Fig. 2).

During the second experiment, diurnal inside airhumidity was very low from June 28 to July 2, with RHvalues of 24–40%, and then it reached 50–75% (July 3–18) (Fig. 1). The weather was windy, with frequentchanges of both direction and wind speed, and withpeaks at 3–6 m s¡1. The airXow recorded inside tunnels inthe Eastern border row ranged from 0.3 to 1.3 m s¡1

according to outside wind speed and direction (Fig. 2).In contrast, the airXow in the central rows ranged fromonly 0.0 to 0.3 m s¡1 (Fig. 2). Consequently, humidityconditions prevailing in Eastern border row plants werelower than that of center row plants (Fig. 1), the diVer-ence reached to 18 points of RH during the day but thediVerential was only 3.4 points between RH meansestablished from data recorded during the Experiment 2(Table 1).

In 2002 (Experiments 3 and 4), the weather was moreunstable than conditions expected from the Alénya cli-matic area. During the third experiment (Fig. 3), weatherconsisted of sunny days, cloudy days, and overcast daysin a 1:1:1 proportion. The wind speed was highly vari-able with peaks of Tramontane (320–350°) at 5–7 m s¡1

for the 3 days following the Wrst mycoinsecticide applica-tion, and on May 23–27. Averaged data ranged from 3.5(daytime) and 2.0 m s¡1 (nighttime) with Tramontaneto 1.7 (daytime) and 1.0 m s¡1 (nighttime) withoutTramontane. Solar radiation transmission rates were ca.80% in the glasshouse and ca. 70% in tunnels. Climaticparameters inside any of the three greenhouse types usedfor experiments varied according to outside weathervariations, but there were diVerences mainly caused bythe speciWc ventilation systems (Table 2). The air humid-ity recorded in the glasshouse was substantially higherthan outside (40 points of RH at nighttime, on May 18)and to a lesser extent than that observed in both conven-tional and highly ventilated tunnels (Table 2, Fig. 3).TheairXow in the glasshouse ranged from 0.08 to 0.4 m s¡1,with peaks of 0.7–0.8 m s¡1 on May 21 and 22 (outsidewind speed observed at 8 m s¡1). In the conventional tun-nel, diurnal temperatures (maxima at 30–32 °C) werehigher than outside and temperatures recorded in theglasshouse (Table 2, Fig. 3). For the Wrst 6 days of Exper-iment 3, air humidity in the conventional tunnel

exceeded 60 RH% for more than 16 h per day. AirXow atdaytime (mean at 0.16 m s¡1, and maxima at ca.0.3 m s¡1) was lower than in the glasshouse (mean at0.21 m s¡1, and maxima at ca. 0.6 m s¡1) (Table 2). Condi-tions prevailing in the highly ventilated tunnel werecloser to outside conditions. The inXuence of additionalopenings depended on the location inside this tunnel; itwas lower in the central part, where tomato plants wereselected for assays than in the end of plant rows, close tothe gable end openings.

During the fourth experiment, outside temperatureswere lower than expected in the Alénya area (Table 2,Fig. 3). Global radiation and wind were highly variable.

Fig. 3. Variation of ambient humidity and temperature outside and indiVerent tested environments: traditional tunnel, highly ventilated tun-nel, and glasshouse, during the critical periods of time for fungus infec-tion of T. vaporariorum larvae in Experiments 3 and 4 (May 17–25,and July 1–9, 2002, respectively).

J. Fargues et al. / Biological Control 32 (2005) 461–472 467

However, the North-Westerly Tramontane (310–350°)was dominant, with an intensive period of peaks at 6–9 m s¡1 from July 13 to 18. Diurnal temperature andhumidity were higher inside the conventional tunnelthan outside (diVerentials reaching to ca. 3 °C and 20–30points of RH), and to a lesser extent than inside thehighly ventilated tunnel (diVerentials up to ca. 2 °C and12–14 points of RH) (Table 2, Fig. 3). Maximal airXowrecorded in central rows reached ca. 0.3 m s¡1 inside the

Fig. 4. Variation of ambient humidity (at 30-cm distance from leaves)and leaf boundary layer (at 5-mm distance from the under leaf surface)in central row plants in the traditional tunnel for 5 days in Experiment3 (May 21–26, 2002).

conventional tunnel and 0.35 m s¡1 inside the highly ven-tilated tunnel, and diurnal airXow means were 0.11 and0.13 m s¡1, respectively (Table 2).

In all tested situations (in 2001 and in 2002), insideair humidity was dependent on greenhouse conWne-ment. Additionally, air characteristics showed substan-tial diVerences between the bulk air humidity measuredat 30 cm distance from the leaves and the air humidityof the under-leaf boundary layer recorded at a distanceof 5 mm from the leaf surface (Tables 1 and 2). Forexample, in the canopy of the center row plants of theconventional tunnel, this RH diVerential reached 29points of RH during the day and 12 points during thenight (Fig. 4).

3.2. EVect of mycoinsecticide applications

3.2.1. Experiment 1The artiWcial infestation provided relatively homoge-

neous populations (second- instar through empty pupalcases) ranging from ca. 120 insects per sampled leaf incontrol plants located in the central row to 204 in con-trol plants in the border row (F D 0.14; df D 4,77;P D 0.172) (Table 3).

Cumulative mortality occurring in all instars variedsigniWcantly (F D 29.288; df D 4,77; P < 0.001) (Table 3).Total cumulative larval mortality on treated plantsranged from 53% (central row plants) to 69% (windward

Table 2Climatic conditions prevailing in the diVerent greenhouse structures used for Experiments 3 and 4

Averaged data (§SD).a Climate measurements performed outside at 5 m high and 50 m from the greenhouses(x) and in the center of each greenhouse above the

canopy(y).b Small sensors in the leaf boundary layer at 5 mm from the under-leaf surface(y).c Thin thermocouples pricked in the middle vein on the under-leaf surface(y).

Experiment 3 (May 17–June 10, 2002) Experiment 4 (July 1–24, 2002)

Outsidex Glasshousey Conventionaltunnely

Highly ventilatedtunnely

Outsidex Conventionaltunnely

Highly ventilatedtunnely

Air speed (m s¡1)a

Daytime (8:00–20:00 h) 2.56 § 1.05 0.21 § 0.15 0.16 § 0.06 0.19 § 0.07 2.69 § 1.39 0.11 § 0.05 0.13 § 0.07Nighttime (20:00–8:00 h) 1.60 § 1.3 0.08 § 0.04 0.09 § 0.03 0.10 § 0.05 2.08 § 1.04 0.06 § 0.02 0.08 § 0.03

Air temperature (°C)a

Daytime 20.9 § 3.2 22.3 § 3.3 23.1 § 4.4 21.5 § 3.7 24.5 § 1.7 25.0 § 2.6 24.4 § 2.1Nighttime 16.7 § 2.3 16.6 § 2.2 15.8 § 2.7 15.7 § 2.8 20.8 § 1.8 19.2 § 2.0 20.1 § 1.9

Leaf boundary layer temperature b

Daytime 21.5 § 3.3 24.4 § 4.2 21.6 § 3.4 24.4 § 2.7 23.7 § 2.4Nighttime 16.2 § 2.1 15.3 § 2.7 15.1 § 2.4 18.5 § 2.2 18.8 § 2.0

Leaf surface temperaturec

Daytime 21.5 § 2.9 20.8 § 3.6 20.8 § 4.2 23.0 § 2.6 22.9 § 2.0Nighttime 17.5 § 2.1 14.1 § 2.6 16.1 § 2.4 17.7 § 2.2 19.4 § 1.9

Air humidity (RH%) a

Daytime 59.2 § 14.8 71.5 § 13.5 70.4 § 9.1 68.0 § 10.4 57.8 § 12.9 75.4 § 10.0 68.9 § 11.7Nighttime 75.5 § 10.9 90.4 § 6.5 87.7 § 7.7 82.4 § 9.7 71.9 § 12.9 84.4 § 9.9 75.8 § 11.4

Leaf boundary layer humidityb

Daytime 87.7 § 12.4 87.7 § 9.6 84.0 § 7.3 86.9 § 7.9 80.9 § 10.2Nighttime 100 § 9.0 92.1 § 7.3 91.3 § 7.4 93.8 § 5.4 87.7 § 7.8

468 J. Fargues et al. / Biological Control 32 (2005) 461–472

T

able

3E

Vec

t of

gre

enho

use

clim

ate

hete

roge

neit

y on

L. m

usca

rium

infe

ctiv

ity

tow

ards

T. v

apor

ario

rum

larv

ae o

n to

mat

o in

Exp

erim

ents

3 a

nd 4

Num

ber

of w

hite

Xy

larv

ae a

nd m

orta

lity

in y

oung

larv

ae a

nd in

tota

l lar

vae,

rec

orde

d 16

and

19

days

aft

er th

e W

rst f

unga

l app

licat

ion

(May

21

and

June

29,

200

1, r

espe

ctiv

ely)

per

sam

pled

leaf

. (a,

b)M

eans

wit

hin

a co

lum

n fo

llow

ed b

y th

e sa

me

lett

er a

re n

ot s

igni

Wca

ntly

diV

eren

t (A

NO

VA

pro

cedu

re; �

D0.

05; S

NK

tes

t).

AM

eans

of

data

(x

§SE

M),

expr

esse

d as

loga

rith

mic

val

ue [l

og (

num

ber

of w

hite

Xie

s+1)

]. (N

o tr

ansf

orm

ed d

ata

in b

rack

ets)

.B

Arc

sine

-tra

nsfo

rmed

mor

talit

y da

ta§

SEM

exp

ress

ed in

deg

rees

(%

val

ues

in b

rack

ets)

.

Loc

aliz

atio

nE

xper

imen

t 1

(May

21–

June

5, 2

001)

Exp

erim

ent

2 (J

une

29–J

uly

18, 2

001)

Log

-No.

W

hite

Xie

s/sa

mpl

eA

live

and

dead

Arc

sine

larv

al m

orta

lityB

Cum

ulat

ive

mor

talit

yL

og-N

o.W

hite

Xie

s/sa

mpl

eA

live

and

dead

Arc

sine

larv

al m

orta

lityB

Cum

ulat

ive

mor

talit

yP

aras

itis

m

pred

atio

n le

vel

Nat

ural

and

fu

ngus

-cau

sed

mor

talit

y

Par

asit

ism

pr

edat

ion

leve

lN

atur

al a

nd

fung

us-c

ause

d m

orta

lity

Eas

tern

bor

der

row

Con

trol

2.31

§0.

09 (

204)

17.3

§2.

7 a

(9%

)21

.1§

2.1

c (1

3%)

30.3

§2.

2 c

(26%

)2.

54§

0.04

b (

347)

22.7

§2.

4 a

(15%

)24

.8§

1.6

c (1

8%)

36.2

§1.

9 b

(35%

)L

eew

ard

plan

tsL

. mus

cari

um2.

13§

0.05

(13

5)6.

5§

2.0

b (1

%)

51.6

§2.

8 a,

b (6

1%)

53.3

§2.

7 a,

b (6

4%)

2.76

§0.

04 a

(57

5)19

.4§

1.9

a,b

(11%

)48

.3§

1.4

b (5

6%)

56.5

§1.

8 a

(70%

)

Win

dwar

d pl

ants

L. m

usca

rium

2.22

§0.

06 (

166)

6.3

§1.

9 b

(1%

)54

.3§

3.6

a (6

6%)

56.1

§3.

4 a

(69%

)2.

74§

0.04

a (

550)

14.8

§2.

0 b

(7%

)48

.8§

2.8

b (5

7%)

54.2

§2.

5 a

(66%

)

Cen

tral

row

Con

trol

2.08

§0.

04 (

120)

15.9

§2.

4 a

(8%

)18

.0§

1.3

c (1

0%)

25.8

§1.

7 c

(19%

)2.

43§

0.06

b (

269)

20.1

§3.

5 a

(12%

)30

.1§

1.4

c (2

5%)

38.6

§3.

0 b

(39%

)L

. mus

cari

um2.

17§

0.08

(14

8)4.

9§

1.4

a (1

%)

45.6

§2.

1 b

(51%

)46

.6§

5.5

b (5

3%)

2.84

§0.

03 a

(69

2)10

.6§

0.9

c (3

%)

57.8

§2.

0 a

(72%

)60

.8§

2.0

a (7

6%)

plants in the wind-exposed border row). In controls,

mortality rates were less than 26%. There was a weakeVect of the climate heterogeneity on fungus-inducedmortality caused by a relatively lower mortality rate incentral row plants (53%), but this rate did not diVer fromthat noted in leeward plants of the border row (Table 3).Parasitism was insigniWcant. Predation did not exceed9%, but its rates were signiWcantly higher in controls (8and 9% in central row plants and in border row plants,respectively) than in fungus-treated plants (<1%)(F D 8.863; df D 4,77; P < 0.001) (Table 3).

3.2.2. Experiment 2Total populations collected on leaves ranged from

269 (in water-sprayed central row plants) to 692 insects(in fungus-treated central row plants) (F D 14.868;df D 4,83; P < 0.001) (Table 3).

Cumulative mortality occurring in all instars variedsigniWcantly between treatments (F D 23.783; df D 4,83;P < 0.001) (Table 3). Fungal-induced mortality diVeredsigniWcantly from controls in central row plants (76%compared to 39%) as well as in both windward and lee-ward border row plants (68 and 70%, respectively, com-pared to 35%) (Table 3). Parasitism was negligible.Predation did not exceed 15%, but its rates were gener-ally relatively higher in controls (12 and 15%,) than infungus-treated plants (from 3 to 11%) (F D 5.801;df D 4,83; Px< 0.001) (Table 3).

3.2.3. Experiment 3The artiWcial infestation provided population levels

ranging from 176 insects per sampled leaf collected fromfungus-treated plants to 366 insects per sampled leaf col-lected from control plants, both in the “highly venti-lated” tunnel (Table 4). There was no signiWcant eVect ofboth ventilation system and fungus applications on pop-ulation levels expressed in log (x + 1) (F D 2.186;df D 5,60; P D 0.068).

Total cumulative mortality occurring in both youngand old larvae in controls ranged from 12.0 to 18.8%,while that observed in fungus-treated plants rangedfrom 89.5 to 93% (treatment eVect F D 725.198; df D 2,59;P < 0.001) (Table 4). There was no signiWcant eVect of theventilation system on either total cumulative mortality(F D 0.173; df D 2,59; P D 0.842) or fungus-inducedcumulative mortality (F D 2.263; df D 2,59; P D 0.113).Fungus-induced mortality occurred mainly in Wrst- andsecond-instar larvae (mortality rates ranged from 64.6 to74.9%) (Table 4). Cumulative mortality rates caused byparasitism and predation were low (from 0.1 to 7.8%),and they were dependent on the absence of fungus treat-ment (F D 36.309; df D 1,59; P < 0.001).

3.2.4. Experiment 4Population density was more homogeneous in this

experiment. Population levels ranged from 224 insects

J. Fargues et al. / B

iological Control 32 (2005) 461–472

469

Table 4EVect of climatic manageme in Experiments 3 and 4

Number of whiteXy larvae a al applications (May 17 and July 1, 2002, respectively) per sampled leaf. (a,b) Meanswithin a column followed by st).

A Means of data (x § SEM ata in brackets).B Arcsine-transformed m

Climatic regime andtreatment

Experiment 4 (July 1–24, 2002)

Log-No.WhiteXies/sampleA

live anddead

Arcsine larval mortalityB

Parasitismpredationlevel

Natural and fungus-causedmortality

Cumulativemortality

Young larvae

All larvae

GlasshouseControl

— — — — —

GlasshouseL. muscarium

— — — — —

Greenhouse control 2.46 § 0.05 (288)

45.6 § 2.6 a (51%)

7.1 § 1.6 d (2%)

24.8 § 2.3 d (18%)

57.6 § 2.6 d (71%)

GreenhouseL. muscarium

2.51 § 0.5 (324)

9.7 § 1.1 c (3%)

58.8 § 2.1 a (59%)

74.9 § 1.2 a (93%)

79.9 § 1.5 a (97%)

Opened greenhousecontrol

2.47 § 0.06 (295)

48.0 § 2.2 a (55%)

22.4 § 2.7 c (22%)

34.0 § 2.1 c (31%)

70.2 § 2.2 c (89%)

Opened GreenhouseL. muscarium

2.35 § 0.07 (224)

21.5 § 1.9 b (13%)

51.4 § 1.8 b (51%)

64.2 § 1.6 b (81%)

78.3 § 1.5 a (96%)

nt on L. muscarium infectivity towards Trialeurodes vaporariorum larvae on tomato

nd mortality in young larvae and in total larvae, recorded 24 days after the Wrst fung the same letter are not signiWcantly diVerent (ANOVA procedure; � D 0.05; SNK te), expressed as logarithmic value [log (number of whiteXies + 1)]. (No transformed d

ortality data § SEM expressed in degrees (% values in brackets).

Experiment 3 (May 17–June 10, 2002)

Log-No.WhiteXies/sampleA

live anddead

Arcsine larval mortalityB

Parasitismpredationlevel

Natural and fungus-causedmortality

Cumulativemortality

Young larvae

All larvae

2.50 § 0.08 (315)

5.9 § 2.8 bc (1.0%)

0.0 § 0.0 c (0%)

18.1 § 2.4 b (9.7%)

20.3 § 3.0 b (12.0%)

2.37 § 0.06 (231)

1.0 § 1.0 c (0.1%)

59.9 § 3.0 a (74.9%)

74.4 § 1.7 a (92.8%)

74.7 § 1.7 a (93.0%)

2.39 § 0.12 (366)

16.2 § 4.1 a (7.8%)

0.0 § 0.0 c (0%)

15.1 § 1.5 b (6.8%)

23.9 § 3.6 b (16.4%)

2.33 § 0.05 (176)

5.0 § 1.2 c (0.8%)

53.5 § 2.9 a (64.6%)

69.9 § 2.0 a (88.2%)

71.1 § 2.0 a (89.5%)

2.56 § 0.09 (245)

11.9 § 2.8 a,b (4.3%)

9.7 § 2.9 b (2.9%)

20.5 § 2.7 b (12.3%)

25.7 § 2.1 b (18.8%)

2.25 § 0.08 (212)

0.4 § 0.4 c (0.1%)

59.7 § 1.6 a (74.5%)

71.8 § 1.7 a (90.3%)

71.9 § 1.2 a (90.4%)

470 J. Fargues et al. / Biological Control 32 (2005) 461–472

per sampled leaf collected on plants treated with Myc-otal in the highly ventilated tunnel to 324 insects in theconventional tunnel (F D 1.30; df D 1,59; P D 0.283)(Table 4).

Unexpected cumulative mortality rates were observedin controls (71 and 89%) (Table 4). A great part of thismortality was due to predation with 51% of control lar-vae in the conventional tunnel and 55% in the highlyventilated tunnel. In fungus-treated larvae, both parasit-ism and predation provoked only 3 and 13% mortality,respectively. In contrast, natural (without parasitism andpredation) and fungus-induced mortality that occurredin young larvae was signiWcantly higher in fungus-treated larvae (59 and 51%) than in controls (2 and 22%)(treatment eVect, F D 236.950; df D 1,59; P < 0.001).Cumulative fungus-induced mortality (without preda-tion) occurring in all instars conWrmed the strong eVectof the fungus treatment (93 and 81%, respectively) (treat-ment eVect, F D 159.216; df D 1,59; P < 0.001).

In this experiment, fungus-induced mortalityoccurred mainly in young larvae, whereas predationstarted later, when larvae surviving the fungus applica-tions reached the fourth larval instar. In addition, natu-ral introductions of adults of the entomophagous bug,Macrolophus caliginosus, were observed in greenhousesduring the last 10 days of the Experiment 4.

4. Discussion

Recent studies showed a high control potential of theHyphomycetes, B. bassiana, P. fumosoroseus, and L.lecanii for whiteXies under relatively dry ambient condi-tions in laboratory assays (Vidal et al., 2003; Wraightet al., 1998) and in small-scale Weld trials (Fargues et al.,2003; Wraight et al., 2000), although high humidity con-ditions were considered as an absolute requirement forfungus-induced infection (Drummond et al., 1987;Ekbom, 1979, 1981; Hall and Burges, 1979; Hall, 1985;Osborne and Landa, 1992; Riba and Entcheva, 1984).

Fargues et al. (2003) did not Wnd any change in thepathogenic activity of B. bassiana and L. lecanii towardswhiteXy nymphs in glasshouse tomato crops using a cli-matic management strategy, which provided daily peri-ods of high humidity (>90%) 2 or 3 h shorter in “dry”compartments than in “humid” ones. The authors sug-gested that the high mortality in whiteXy nymphsobserved at moderate humidity in northern Mediterra-nean glasshouses could be explained by the conditionsprevailing in the insect niche, i.e., in the under-leafboundary layer (Boulard et al., 2002). The characteristicsof this leaf boundary layer depend on both aerodynamicresistance and stomatal resistance (Boulard et al., 2002;Pachepsky et al., 1999; Schuepp, 1993; Vesala, 1998). Incommercial Mediterranean greenhouse tomato crops,there are minimal limitations of the plant physiological

activity caused by environmental factors, like lower solarradiation or deWcient water. In contrast, windy condi-tions, frequent in the South of France, were able toinduce substantial changes of the air bulk within thecanopy. In situ measurements showed that tomatoplants more directly or indirectly exposed to wind, likeplants facing the vent openings in the conventional tun-nel and central row plants of the highly ventilated tunnelglasshouses, were submitted to humidity conditionscloser to outside conditions, compared to that measuredin central row plants in conventional tunnels. Despitethe relative disconnection between the conditions of can-opy air bulk and the conditions of the leaf boundarylayer (Boulard et al., 2002; Schuepp, 1993), the microcli-matic heterogeneity of greenhouses (Papadakis et al.,1996; Sase and Takakura, 1984; Yang, 1995) can lead tosome variations of the leaf boundary layer according tothe spatial location of plants within the greenhouse can-opy (Schuepp, 1993). Experimental and simulation dataprovided by Boulard et al. (2004) conWrmed that micro-meteorological characteristics of the leaf boundary layerwere aVected in wind-exposed situations. However, ourresults showed that there was no eVect of the air Xowvelocity on the fungus-induced infection in whiteXynymphs on exposed plants. Apparently, the humidityconditions prevailing in the thin layer (<1 mm) close tothe under-leaf surface, where nymphs are Wxed, were notdrastically aVected by any of the tested situations, interms of both humidity threshold and period of time athigh humidity required for infection (Drummond et al.,1987; Ekbom, 1981; Fargues and Luz, 2000; Luz andFargues, 1999; Milner and Lutton, 1986).

Our results conWrmed the potential of Hyphomycete-based mycoinsecticides for whiteXy control in green-house tomato crops in the northern Mediterranean areaunder usual meteorological conditions. The implementa-tion of operational pest management strategies based onthe use of mycoinsecticides in greenhouses must takeinto account pertinent factors that determine the condi-tions prevailing in the habitat of the targeted whiteXylarvae and not only the overall inside climate nor themicrometeorological heterogeneity inside the canopy.

Acknowledgments

We are very grateful for the technical collaboration ofB. Serrate, J.-M. Thuillier, and H. Vermeil de Conchard(INRA/CBGP) and for the technical assistance of L.Argoud, A. Le Saint, A. Martinez, G. Remaque, and N.Terman. We acknowledge Dr. Mark Goettel from Agri-culture and Agri-Food Canada (Lethbridge ResearchCentre, Alberta) and Dr. William Meikle from the Euro-pean Biological Control Laboratory (USDA/ARS/EBCL, Montpellier, France) for critical comments onthe manuscript. We thank Koppert B.V. for providing

J. Fargues et al. / Biological Control 32 (2005) 461–472 471

the Mycotal for experiments. Mention of a proprietaryproduct does not constitute an endorsement or a recom-mendation for its use. This research was jointly sup-ported by a strategic grant from the French Researchand Technology Ministry and the Région Languedoc-Roussillon, France.

References

Bolckmans, K., Sterk, G., Eyal, J., Sels, B., Stepman, W., 1995. Pre-FeRal, (Paecilomyces fumosoroseus (Wize) Brown and Smith, strainApopka 97), a new microbial insecticide for the biological controlof whiteXies in greenhouses. Med. Fac. Landbouww. Univ. Gent.60, 719–724.

Boulard, T., Mermier, M., Fargues, J., Smits, N., Rougier, M., Roy, J.C.,2002. Tomato leaf boundary layer climate: implication for microbi-ological control of whiteXies in greenhouse. Agric. Forest Meteorol.110, 159–176.

Boulard, T., Fatnassi, H., Roy, J.-C., Lagier, J., Fargues, J., Smits, N.,Rougier, M., Jeannequin, B., 2004. EVect of conWnement on airhumidity in tunnels and in the leaf boundary layer: implications forbiological control of greenhouse crops. Agric. Forest Meteorol.125, 225–239.

Drummond, J., Heale, J.B., Gillepsie, A.T., 1987. Germination andeVect of reduced humidity on expression of pathogenicity in Verti-cillium lecanii against the glasshouse whiteXy Trialeurodes vapora-riorum. Ann. Appl. Biol. 111, 193–201.

Ekbom, B.S., 1979. Investigations on the potential of a parasitic fungus(Verticillium lecanii) for biological control of the greenhousewhiteXy (Trialeurodes vaporariorum). Swed. J. Agric. Res. 9, 129–138.

Ekbom, B.S., 1981. Humidity requirements and storage of the entomo-pathogenic fungus (Verticillium lecanii) for use in greenhouses.Ann. Entomol. Fenn. 47, 61–62.

Faria, M., Wraight, S.P., 2001. Biological control of Bemisia tabaci withfungi. Crop Prot. 20, 767–778.

Fargues, J., Luz, C., 2000. EVects of Xuctuating moisture and tempera-ture regimes on the infection of Beauveria bassiana for Rhodniusprolixus. J. Invertebr. Pathol 75, 202–211.

Fargues, J., Vidal, C., Smits, N., Rougier, M., Boulard, T., Mermier, M.,Nicot, P., Reich, P., Jeannequin, B., Ridray, G., Lagier, J., 2003. Cli-matic factors on entomopathogenic Hyphomycetes infection ofTrialeurodes vaporariorum (Homoptera: Aleyrodidae) in Mediter-ranean glasshouse tomato. Biol. Control 28, 320–331.

Fransen, J.J., 1990. Natural enemies of whiteXies, fungi. In: Gerling, D.(Ed.), WhiteXies: Their Bionomics, Pest Status and ManagementIntercept. Andover, UK, pp. 187–210.

Fruit, L., Nicot, P.C., 1999. Biological control of Botrytis cinerea ontomato stem wounds with Ulocladium atrum. IOBC/WPRS Bull.22, 81–84.

Gervais, A., Lorendeau, J.Y., Pelloux, G., Reich, P., Lagier, J., Pyrrha,P., 1996. Syspil, un système de pilotage intégré pour la conduite duclimat des serres, Actes Du Séminaire De L’AIP Serres. INRA,Avignon France pp. 256–265.

Hall, R.A., 1985. WhiteXy control by fungi. In: Hussey, N.W., Scopes,N. (Eds.), Biological Pest Control, The Glasshouse Experience.Blandford Press, Poole, Dorset, UK, pp. 116–118.

Hall, R.A., Burges, H.D., 1979. Control of aphids in glasshouses by thefungus Verticillium lecanii. Ann. Appl. Biol. 93, 235–246.

Helyer, N., Gill, G., Bywater, A., Chambers, R., 1992. Elevated humidi-ties for control of chrysanthemum pests with Verticillium lecanii.Pestic. Sci. 36, 373–378.

Lacey, L.A., Fransen, J.J., Carruthers, R.I., 1996. Global distribution ofnaturally occurring fungi of Bemisia, their biologies and use as bio-

logical control agents. In: Gerling, D., Mayer, R. (Eds.), Bemisia1995: Taxonomy, Biology, Damage, Control and Management,Intercept. Andover, UK, pp. 401–433.

Luz, C., Fargues, J., 1999. Dependence of the entomopathogenic fun-gus, Beauveria bassiana on high humidity for infection of Rhodniusprolixus. Mycopathologia 146, 33–41.

Milner, R.J., Lutton, J.J., 1986. Dependence of Verticillium lecanii(Fungi: Hyphomycetes) on high humidities for infection and sporu-lation using Myzus persicae (Homoptera: Aphididae) as host. Envi-ron. Entomol. 15, 380–382.

Osborne, L.S., Landa, Z., 1992. Biological control of whiteXies withentomopathogenic fungi. Fla. Entomol. 75, 456–471.

Pachepsky, L.B., Ferreyra, R.A., Colling, D., Acock, B., 1999. Transpi-ration rates and leaf boundary layer parameters for peanut ana-lyzed with two-dimensional model 2D leaf. Biotronics 28, 1–12.

Papadakis, G., Mermier, M., Meneses, J.F., Boulard, T., 1996. Mea-surement and analysis of air exchange rates in a greenhouse withcontinuous roof and side openings. J. Agric. Eng. Res. 63, 219–228.

Ravensberg, A.C., Malais, M., van der Schaaf, D.A., 1990. Applicationsof Verticillium lecanii in tomatoes and cucumbers to controlwhiteXy and thrips. IOBC/WPRS Bull. 13, 173–178.

Riba, G., Entcheva, L., 1984. InXuence de l’hygrométrie ambiante surl’agressivité comparée de plusieurs Hyphomycètes entomopathogè-nes à l’égard de l’aleurode des serres Trialeurodes vaporariorum(Westw.). Proc. Acad. Agric. France 70, 521–526.

Sase, S., Takakura, T., 1984. Wind testing on airXow and temperaturedistribution of a naturally ventilated greenhouse. Acta Horticult.148, 329–336.

Schuepp, P.H., 1993. Leaf boundary layers. New Phytol. 125, 477–507.Smith, P., 1993. Control of Bemisia tabaci and the potential of Paecilo-

myces fumosoroseus as a biopesticide. Biocontrol News Inf. 14, 71–78.

SPSS, Inc., 1997. SIGMASTAT User’s Guide, version 2.03, SPSS Inc.,Chicago, IL.

van der Pas, R.K., Ravensberg, W.J., de Braver, A.C., van Buysen, A.C.,Malais, M., 1996. A comparison between Mycotal (Verticilliumlecanii) and Aschersonia aleyrodis for the control of whiteXy. IOBC/WPRS Bull. 19, 200–203.

van Lenteren, J.C., Noldus, L.P.J.J., 1990. WhiteXy-plant relationships:behavioural and ecological aspects. In: Gerling, D. (Ed.), White-Xies: Their Bionomics, Pest Status and Management Intercept.Andover, UK, pp. 47–89.

van Lenteren, J.C., van Roermund, H.J.W., Sütterlin, S., 1996. Biologi-cal control of Greenhouse WhiteXy (Trialeurodes vaporariorum)with the parasitoid Encarsia formosa: How does it work? Biol.Control 6, 1–10.

Vesala, T., 1998. On the concept of leaf boundary layer resistance forforced convection. J. Theor. Biol. 194, 91–100.

Vidal, C., Fargues, J., Rougier, M., Smits, N., 2003. EVect of air humid-ity on the infection potential of hyphomycetous fungi as mycoin-secticides for Trialeurodes vaporariorum. Biocontrol Sci. Technol.13, 183–198.

Wraight, S.P., Carruthers, R.I., Jaronski, S., Bradley, C., Galaini-Wraight, S., Britton, J., Underwood, N., Sattler, A., Garza, J., 1994.Laboratory and Weld eYcacy of Paecilomyces fumosoroseus andBeauveria bassiana against the silverleaf whiteXy, Bemisia argentifo-lii. In: Proc. VIth Intern. Coll. Invertebr. Pathol. Microbial Control,vol. 2. Montpellier, France, pp. 302–303.

Wraight, S.P., Carruthers, R.I., Bradley, C.A., Jaronski, S.T., Lacey,L.A., Wood, P., Galaini-Wraight, S., 1998. Pathogenicity of theentomopathogenic fungi Paecilomyces spp. and Beauveria bassianaagainst the Silverleaf WhiteXy, Bemisia argentifolii. J. Invertebr.Pathol. 71, 217–226.

Wraight, S.P., Carruthers, R.I., Jaronski, S.T., Bradley, C.A., Garza,J.C., Galaini-Wraight, S., 2000. Evaluation of the entomopatho-genic fungi Beauveria bassiana and Paecilomyces fumosoroseus for

472 J. Fargues et al. / Biological Control 32 (2005) 461–472

microbial control of the silverleaf whiteXy, Bemisia argentifolii.Biol. Control 17, 203–217.

Wright, J. E., 1992. WhiteXies: Development of Naturalis-L, abiorational mycoinsecticide for control. In: Herber, D. J., Rich-ter, D. A. (Eds.), Proc. Beltwide Cotton Conf., vol. 2, pp. 887–888.

Wright, J.E., 1995. Naturalis-LTM: a biological product (Beauveria bas-siana JW-1) for control of crop and greenhouse insects. In: Servizi,M.A.F. (Ed.), Microbial Control Agents in Sustainable Agriculture.Servizi, Torino, Italy, pp. 109–115.

Yang, X., 1995. Greenhouse micrometeorology and estimation of heatand water vapour Xuxes. J. Agric. Eng. Res. 61, 227–238.