Proceedtngs of the 7th IntertUltuYnal Worhng Conference an Stored-product Protection - Volume 2

Pests in tobacco storehouses and their control in China

Cheng Xmgsheng, WeI chongsheng and Wang Fangxiao'

Abstract

Dunng storage tobacco leaves are often subject to manykinds of pests, thus suffer losses both m weights andquahty Investigations demonstrate that there exist as manyas 79 pest species m Chmese tobacco leaf storehouses, thesespecies belong to 7 orders and 31 families Among them,tobacco moth (Ephest~a elutella Hubner) and cigarettebeetle (Lastoderma serricome Fabncius ) are the mostwidespread and harmful, and Tenebroides mauruomicusL., Attagenus piceus Ohver , Triboliurn. caslaneumHerbst, L~POSCelLS bost17Jchophilus Badonnel sometimesalso presents large quantity and causes certam damages.Chemical treatments are the principal method m

controllmg the pests The pyrethnns and DDVP aregenerally used to treat empty storehouses. or to kill thetobacco moth larvae crawlmg out from tobacco to be able tohve through the Winter Some factones utilize methylbromide and phosphine for furmgation In recent years, Ithas been possible to make use of methoprene due to theintroduction of the threshmg and redrymg Today, there are'already three factones that adopt this pesticide that hasproved to be a successful one. Another, serncomne ISintroduced to predict CIgarette beetle occurrence.Furthermore, the mcreasmg extent of regroupmg mCIgarette mdustryand the technological switch from arnfrcialfermentation to natural aging cause the growing amount ofstored tobacco leaves. The chmbmg pnces of tobacco leavesmade tobacco fuushed products more expensive TheChmese factones are mcreasmgly aware of the Importance ofpests control in tobacco storehouses and this work shall see agreat development m Chma.

Introduction

Chma IS an important tobacco producer With ItS yields ofleaves and CIgarettes rankmg fIrst m the world. Thereforetobacco mdustry exerts much mfluence on the economy ofsuch a developmg country. As well as at field growth stage,leaves durmg storage are also subject to various pests andconsequently lose weight and Usablhty. In this article we

1 Hefel Institute of Econonucs and Technology. Hefel, 230052,Chma

present the general SItuation about occurrence, damage andcontrol of the pests in Chma.

Occurrence of Pests ofStored Tobacco Leaves

Pests discovered in tobacco leaf storehouses, as mdicated anmvestrgation m 20 factones of nearly 10 provinces, mcludeas many as 79 species. of which 73 belong to 28 fanuhes, 5order of insects: 1 to a farruhes, an order of Arachmda.Tobacco beetles and tobacco moths are most Widespread andmost harmful Tenebrouies mauriianicus L, Attagenuspiceus Ohvier , Tribolium. caeianeuni Herbst, andLiposceue brotrychophLlus Badonnel also occur in certamregions m relatively large numbers and cause certain losses.

Cigarette beetle (Lasioderma serricorne Fabricius)

A lot of studies demonstrated that 20 - 30°C and RH 70-80% are most suitable for the survival and reproduction ofthe species. Too high or too Iowa temperature or humidityinhibits ItS growth and development. China IS broad and ItSchmate vanes markedly from south to north areas South ofthe Yangtze RIver belongs to subtropical zone, wheretemperatures are much higher m wmter and humidity keephigher all the year than m the northern part of Chma Inconsequence, CIgarette beetles occur senously in thesouthern areas For example, in Hefei , Anhui Provimce,the number of generations per year IS 2 - 3; m Changsha,Hunan Provmce , 3-4; m Xiamen, Fujian Province, 4-5By contrast, m areas north of the Yellow RIver, cigarettebeetles can not survive through the Winter Although theannual accumulated temperatures are enough for severalgenerations, It ISrare for them to occur m great quantities.Only m a few Circumstances, e g , when temperatures mspnng or m summer are relatively high and adequate fortobacco beetles, pests earned on leaves transported fromsouth Willreproduce qmckly and pose damages.It was also found, accordmg to the mvestigation, that

CIgarette beetles occurred more severely on the leaves thathad been stored for 12 - 24 months Mter 24 months ofstorage, as a result of overalcohohzation and deterioration ofsome phYSIcaland chemIcal properties of the leaves, growthand development of cigarette beetles was instead mverselymfluenced and theIr population denSIty decreased to someextent For mstance, the results of our studies in Hefeishowed that for mIddle class leaves at one year, two years or

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Proceedmqs of the 7th International Worhng Conference on Stored-product Protection - Yoiume 2

three to four years m storage, the population densrties ofcigarette beetles were 32.4 kg - 1, 197. 6kg - 1 and 980kg-I

respectively. After being stored for 4 years actually nobeetle was found on the leaves. Besides, SIzes of populationsvary WIth production regions or grades of leaves. On leavesproduced m Yunnan, Guizhou and other areas south of theYangtze RIver, on fair class and supenor leaves, CIgarettebeetles occur severely.

Tobacco moth (Ephessia elutella Hubner)

Tobacco moth IS another pest with large sizes ofpopulation. It IS found all over the country. The number ofgeneration IS 3 in Hubei and Anhui, 3 - 4 m Guizhou, 2 inHenan. Temperatures and humidity mfluence much ItSdevelopment. Tobacco moth larvae show weaker cold-hardmess than CIgarette beetles and can not survive throughthe wmter in northern part of ChmaThe occurrence of tobacco moth also bears relations to

such factors as leaf grades, stormg locations, stonngpenods, leaf moisture content etc. The adults havepropensities in laying eggs, prefernng fair class and supenorleaves to mfenor leaves. Population densities are higher ontobacco bales in the warehouses than on leaf stacks m theopen. As to storage periods, the number of tobacco moths ISthe biggest at two years of storage The higher mositurecontent of the leaves IS, the more eggs there are on theleaves. In accordance With our survey m three tobaccofactories m Anhui Province, the average population densrtiesof tobacco moth larvae m the three factones are 3.24 kg - I ,3.38kg-I and 7.74kg-I respectively.

Other pests

In addition to the aforesaid two species, other commonpests are Tenebroides mauriunucus Linnaeus, Triboliurn.caslaneum Herbst, Attagenues piceus Olrvter , Liposcelisbostrychophilus Badonnel. But their SIzeS of populations aregenerally small and theIr damage to tobacco leaves ISrelatively mmor. For example, our mqUlry mto severaltobacco factones m AnhUl Provmce showed that red flourbeetle and black gram beetle only accounted for 0.41 % and0.39 % of the total pest number m the storehouses.

Damage by Pests of Stored Tobacco

Tobacco IS a speCial kmd of consumer goods. People smokmgCIgarettes Wish a certain amount of mcotme to satisfy theIrphYSIcal reqUIrements, and WIsh good taste and pleasantsmell m the fume as well. Tobacco leaf IS the pnnclpal

matenal m manufactunng CIgarettes. Makmg high-gradeCIgarettes need high quality leaves. Thus, damage by pestsmeans not only leaf weight loss. What IS worse, pests makecavities wlule feedmg and reduce YIeld of cutting and leavebehmd a lot of feces and dead bodies wluch pollute leaves andspoil leaf taste

Leaf weight losses

The Chmese General Tobacco Company has orgamzed twonationwide surveys of the damage caused by stored tobaccopests. The results were as follows: (1) Leaves contmuallylost weight dunng storage (2) Weight loss was especiallysharp withm the first two years, and then slowed down. (3)The average weight loss percentages m the whole countrywere 1.58% for fair class leaves and 1.81 % for supenorleaves, at one year of storage. (4) Weight loss percentagesmay vary from area to area, smce pests show taxis towardscertam production districts (Table 1) It can be seen fromTablel , that leaves produced south of the Yangtze RIver hadhigher population densrties and rates of damage ThIS canactually be explamed by the differences in leaf quahties thatleaves grown m areas south of Yangtze RIver are nch inchemical compositions and have large water capacity andthus can be served as flavonng tobacco, while leavescultivated in northern part, which have high fiber contentand can be mamly used as fillers to which pests show lesstaXIS and slower population growth speed. (5) Stonnglocations also affect damage degree to the same class ofleaves (Table 2). For the M - 3 leaves produced in Henan orYunnan, havmg been stored for one year in some differentplaces, the weight losses were the lowest in Shengyang, thehighest m Xiamen, and displayed a tendency of aggravationof pest damage or weight loss from north to south.Calculatmg on the baSIS of the total amount of stored

leaves in the whole country, of the distnbution of storedleaves, and of damage rate, Chma loses 32.8 million kg ofleaf weight every year dIrectly because of the pests, or55.3352 mIlhon dollars, whIch IS surpnsmg

Influence on yields of cutting

Smce pests feedmg on leaves provoke a lot of caVIties onthem, defect cut tobacco augment whereas YIeld of cuttmgreduce The reduction degree of YIeld of cuttmg IS positivelycorrelated WIth pest population denSIty. Accordmg to anmvestIgatIon, the reduction rate averaged 2.5 % m theareas south of Yangtze RIver and 1 - 1.5 % m the northernregIOns.

Table 1. Pest population denSIties and leaf weIght loss of faIr class leaves of dIfferent production dlstncts (1991).

denSIty (kg-I)weIght loss (%)

HeIlongjIang Shanxi Henan Hunan Yunnan5.8 21.4 29.4 157.6 139.01.14 1.53 1.47 1.84 2.19

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Proceedmae of the 7th lnternatumal Workt'ng Conference on Stored-product Protection. - Yoiume 2

Table 2. Effects of stormg locations on rate of damage by pests.

Henan M-3 Henan M-3 Yunnan M-3 Yunnan M-3Density (kg-I) Damage rate Density (kg-I) Damage rate

Xuzhou 22.3 1.73 45.0 1.10

Chongqmg 26.0 1.15 438.8 2.26

Xiamen 38.2 2.27 68.6 4.76

Shengyang 0 0.25 0.5 0.14

Causes of the severe occurrence of storehouse pests

In the light of some literatures, weight loss percentage indifferent parts of the world is around 1% on an average. InChma the figure is more than 1. 5%, because of: (1) Poorstoring conditions and insufficient stonng capacities ofstorehouses. For some histoncal reasons the Chmesetobacco factories are numerous but small. Therefore thefactones allocate lmuted financial resources m mtroducing orimporting advanced cigarette makmg equipment. Themvestments on storehouse construction are so few thatstoring conditions are poor and stonng capacities areinsufficient. Presently most factories south of Yangtze Riverstore their leaves in the warehouses, lacking seahngconditions and other pest control facihnes being bad. Thebulk of factories north of Yangtze River store leaves m theopen air. The result of the insufficient stonng capacities,leaves of different penod laid in the mixed way was that thepests cross mfesting. (2) Packing matenal not up to pestcontrol standards. In Chmg, tobacco leaves are mostlypacked with gunny bags, few being packed with plastic bagsin combination with paper box packing. Compared Withhogshead packing used abroad, our method shows noprophylactic effects to tobacco beetle and tobacco moth.Such being the case, it is very easy for pests to infest andreproduce. (3) Lack of strict exammation of pest situationbefore allocation and transportation of leaves, which ISfavorable to pest diffusion. In making CIgarettes, differenttobacco leaves have to be blended. Factories must purchasecertam kinds of leaves from different places of the country.Without stnct examination of pest SItuation, pests may bebrought m with leaves and spread. For instance, m thenorth-eastern region of Chma it IS very cold in winter andpests in the storehouses can hardly hve through the winter.But sometimes at the transition moment from spring tosummer, pests do occur only because leaves introduced fromsouth carried pest sources and then all the leaves in thestorehouses got mfested (4) Laying stress on ehmmationbut takmg prevention lightly. In controllmg pests ofstorehouses, factories chiefly rely on chemical methods.However, limited by poor conditions and shortage ofquahfied technicians, only a small proportion of the factonescould use fumigating techniques m the past, and the

majority only sprayed DDVP, deltarmenm or otherpyrethrins to extermmate surface insects WIthoutsatisfactory results.

Current Control Strategies andthe Future Development

In recent years, owing to the progress of China's economicreform, the degree of growmg m tobacco industry hasaugmented, and technologically there is a SWItch fromartificial fermentation to natural alcoholization As a result,the amount of stored leaves has mcreased. Meanwhile therismg pnces of leaves enlarge the proportion of leaves in thetotal costs of CIgarette finish products. Under suchcircumstances, the relevant factones pay more and moreattention to pest control in storehouses. Measures taken areas follows:1. Reinforce storehouse construction and normahzestorehouse management.The Chmese tobacco mdustry administrative departments

have set specific requirements and appropriate standards forstorehouse construction. Now m the provinces south ofYangtze River there are practically no more openwarehouses In Hubei Province alone some 120, 000m2 ofstandard storehouses were built from 1996 to 1997, and thestonng capacity has been mcreased by 384 milhon kg,moreover, the newly built storehouses hold anti-pest gauzenets and can be sealed for furrugatmg. Regardingmanagement, new and old leaves are now put awayseparately; examination of pest SItuation IS mandatorybefore leaf transportation; definite speculations have beenlaid down in routme conservation of leaves.2. Introduce newly tobacco Infestation control method toensure safe stormg of leaves.Methoprene is a kind of msect parahormone OH). Having

fed on leaves treated with lOmglkg methoprene, larvae ofcigarette beetle or tobacco moth can not develop mto normalpupae before dymg. So far three Chmese factories haveintroduced the technique and it has proven to be successful.But since the chemical can only be used on threshing andredrying lmes, its spread is much restricted. Yet China Willset up about 100 threshmg and redrying hnes m its differentparts after the year 2000. ThIS movement, as we believe,

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Proceedings of the 7th hiternatumol Workmg Conference on Stored-product Protectwn - Volume 2

WIll promote a wider use of methoprene. As for how to useother chemicals, many factories take DDVP anddeltarmethrin to treat empty storehouses, or to kill tobaccomoth larvae crawling out from tobacco bale to hve throughwmter Some factories choose methyl bromide and hydrogenphosphide to fumigate storehouses, in order to mhibrt thedevelopment of storehouse pests, which IS a success, too.Sernconme is also used to predicate the outbreak of CIgarettebeetle by some factones.It deserves to be mentioned that some Chinese factones,

while treatmg cured leaves, seal them with plastic coversand put in oxygen-scavengmg cherrucals. Cured leaves, ofwhich water content IS 18% or so, are easy to go mouldyand to get mfested by pests. Tills can be avoided beforeredrymg by the above-mentioned method.Since tobacco mdustry carries weight on the Chmese

economy, the Chinese government attaches Importance toItS progress, e g., found special scientific researchmstrtutions and schools; create the specialty of tobaccostonng, in the hope of enablmg students to grasp knowledgeof routine management of storehouses, to master tobaccoleaf production conservation and pest control techniques.Trammg of this type of specialists WIll greatly change thepresent SItuation of storehouse technician shortage and Willcertamly facilitate the control of tobacco storehouse pests.

References

Chen Xiun, Gao Lianzhao 1995. Tobacco storehoues pestsand control. Guizhou, Guizhou Science and TechnologyPubhshmg House, 195. (In Chmese)

Chen Yongruan, Peng Oinyun. 1995. Ecology ofLasioderma serricorne (F.) and Its control Journal ofHunan Agncultural University. Vol 21(5) 467 - 471. (InChinese)Cheng Xmsheng, Lu Jiasen. 1997. Contact activity ofmethomyl, acepha te, dichlorvos and trichlorfon to tobaccobeetle larva Pesticide. Science and Admmistration, Vol. 18(4) 23 - 24. (In Chinese)Gong Xmwen, Meng Guohng, LI Chuangren. 1995.Adevances m the study of cigarette beetle. Journal ofHubel Agricultural College. Vol. 15 (3) 235 - 240. (InChinese)Hunan Agricatural College. 1996. Chmese tobacco insectstudy-theory and practice. Beijing, China AgariculturalPubhshing House, 248 (In Chinese)Ryan L.. 1995. Post-harvest tobacco infestation control.London. Chapman and Hall, p155. (In Chmese)Wang Mingjie, Zhang xiaoxi. 1995. Studies on time-specificlife table of laboratory population of CIgarette beetles,Lasuxlerma serricorne (F.) . Journal of NanjmgAgricultural University. Vol 18(4), 52-56. (In Chinese)WeI Chongsheng, Wang Fangxiao. 1994. A list of storagetobacco pests and natural enemies in China. Journal ofAnhui Agncultural SCIences. Vol: 22 supplement, 8 - 10.(In Chmese)Wu Zlushan, Chen Jiahua. 1994. Preliminary investigationson tobacco storage pests m Fujian. China Tobacco. Vol 15(1), 31- 34. (In Chinese)#*~~. 1980. '!t:.t.:Lt''"C~!k(77..A~ t..- rJv)0)~~'::'7 t '"C. utt.:"f~?iJf1l. 83:108-117.

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