ScienceAsi 31 (25): 151-158 Insecticide Resistnce of the Green Rice Lefhopper, Nephotettix cincticeps, to the Systemic Insecticides Used for Seedling-Box Appliction Jirpong Jirin,* Nouki Kojim nd Toru Ngt c Uon Rtchthni Rice Reserch Center, P.O. Box 65, Mung, Uon Rtchthni 34,Thilnd. Tsuku Interntionl Centre, 3-6 Koydi, Irki 35-74, Jpn. c Fculty of Agriculture, Irki University, Ami, Irki 3-393, Jpn. * Corresponding uthor, E-mil: jirpongj@ricethilnd.org Received 3 Sep 24 Accepted 13 Dec 24 ABSTRACT: The mortlity nd feeding inhiition of the green rice lefhopper (GLH), Nephotettix cincticeps Uhler, to four systemic insecticides, nmely imidcloprid, crtp, propphos nd disulfoton, were determined y prfilm method. The three locl popultions of GLH with different resistnce levels to orgnophosphtes (OPs) were compred with respect to LC nd FI otined y this testing method. Feeding inhiition t sulethl doses ws most remrkle, with imidcloprid followed y crtp with no regrd to resistnce levels, while feeding inhiition y propphos nd disulfoton ws oserved only with the OPs resistnt GLH. The residul period of imidcloprid grnule (2%) nd crtp grnule (4%) pplied to the seedling-ox were determined in terms of mortlity nd feeding inhiition. Imidcloprid gve the longest residul period of lethl ction nd feeding inhiitory ction. The GLH popultion ws remrkly reduced in the imidcloprid treted plot compred to the untreted plot, while reduction in popultion density ws not oserved in the crtp treted plot. KEYWORDS: feeding inhiition, insecticide resistnce, Nephotettix cincticeps, prfilm method, seedling-ox ppliction. IODUCTION Insecticide resistnce is prolem in ll insect groups tht serve s vectors for cusing plnt diseses, including rice virus diseses. The green rice lefhopper (GLH), Nephotettix cincticeps Uhler, is considered to e one of the devstting insect pests tht hs dpted to series of insecticides used for its control. GLH not only feed on rice plnts, directly cusing yield reduction, ut they lso trnsmit viruses which cuse severe diseses of rice 6. Pest control in Jpn, s in most rice producing countries, hs lrgely relied on insecticides. GLH hs lso long een controlled y insecticides since the introduction of synthetic insecticides fter World Wr II. Extensive use of insecticide hs contriuted to the development of insecticide resistnce in mny field popultions of this species 8. Resistnce of GLH to orgnophosphte insecticides first ppered in Shikoku Islnd in 1961 5. Mny GLH locl popultions resistnt to crmtes nd orgnophosphtes (Ops) hve een reported 4,13. A similr sitution in other groups of insecticides to GLH round Jpn hs continuously een reported 1,12. To overcome the development of insecticide resistnce, miniml use of insecticides is the most importnt point 12. Mechnicl trnsplnting is currently widely used in Jpn. Grnule insecticides re pplied in the seedlingox efore trnsplnting. The insecticides re emedded into the pddy soil ner the root zone nd esily sored y the rice plnt. In this tretment, the systemic insecticides re imied orlly y sucking insects through the plnt tissues, so it is pproprite to estimte insecticide susceptiility through the sme dministrtion wy s the ctul ppliction route of systemic insecticides. In ddition, in this tretment, the insects my void contct with some systemic insecticides y ehvioristic resistnce, which is expected to e more promising strtegy for controlling virus diseses trnsmitted y the vector insects 9,18,19. Considering this viewpoint, we developed specific testing method to determine n insect s susceptiility to systemic insecticides which exert two functions, lethl ction nd feeding inhiitory ction. In this experiment, the occurrences of insecticide resistnce to these systemic insecticides were ssessed nd the residul period of the widely used systemic insecticide, s seedling-ox ppliction, ws determined. MATERIALS AND METHODS Insects The GLH used in this study were collected from
152 ScienceAsi 31 (25) three loctions in Jpn: The Tniym popultion () ws collected from n re intensively treted y insecticide in Kgoshim city, Kgoshim prefecture in 1998. The Tsuku popultion () ws collected Tniym popultion () Ntori popultion () Tsuku popultion () Fig 1. Loction of the three res in Jpn, where the three strins of GLH were collected. The Tniym popultion ws collected from n re intensively treted y insecticide. The Ntori popultion ws collected from less treted re. The Tsuku popultion ws collected from rice field in Tsuku. from Irki prefecture in 2. The Ntori popultion () ws collected from less treted re in Ntori city, Miygi prefecture in 1998 (Fig 1). The nd strins were supplied y Kgoshim Prefecturl Experiment Sttion nd Miygi Prefecturl Experiment Sttion, respectively. The insect colonies were estlished from three locl popultions in plstic cge (34 26 34 cm) nd plced in rering room t 25 C, nd kept under light for 14 h nd in the drk for 1 h t Tsuku Interntionl Centre (TBIC). The insects were mintined on the rice vriety Akitkomchi, which hs no mjor resistnce genes for GLH. Insecticides Four insecticides commonly used for seedling-ox ppliction in Jpn were used in this study. Imidcloprid [1-((6-chloro-3-pyridinyl)methyl)-N-nitro-2- imidzolidinimine] is systemic insecticide chemiclly relted to the tocco toxin, nicotine, cting on the nervous system. Crtp hydrochloride [S,S -(2- (dimethylmino)-1,3-propnediyl) dicrmothiote] is nereistoxin nlogue insecticide. Propphos [4- methylthiophenyl dipropyl phosphte] is n orgnophosphorus insecticide commonly used ginst lefhopper nd plnthopper since 1986. Disulfoton [O,O-diethyl S-(2-(ethylthio)) ethyl phosphoro dithiote] is n liphtic orgnothiophosphte insecticide which ws first used in seedling-ox ppliction. Reduction in its efficcy ws reveled in the lter hlf of the 196s in the Kyushu res nd it ws replced y propphos nd crtp. Concentrtion-Mortlity nd -Feeding Inhiition Biossys (Prfilm Method) Crtp, propphos, disulfoton nd imidcloprid were of technicl grde with purity greter thn 99% nd otined from Wko Pure Chemicl Industries, Ltd., Jpn. The fifteen serils dilutions of insecticide concentrtions (-8 ppm) for ech insecticide were prepred. Three insecticides, nmely imidcloprid, crtp nd propphos, were dministered to the insects s solution diet contining 2.5% sucrose, wheres disulfoton ws dministered s 2.5% sucrose solution contining Tween 6, through n rtificil memrne of stretched thin prfilm 11. A totl of 5 mle dults were nesthetized with cron dioxide nd trnsferred into plstic vil (3 cm in dimeter nd 3 cm in height). The vil ws covered with stretched prfilm nd.3 ml droplet of the diet contining the log concentrtion of the insecticides ws plced on the prfilm, then the droplet ws sndwiched with nother stretched film. The vils were plced t 25 C in 14-h light nd 1-h drk periods, over 6% RH. The experiment ws conducted with 3 replictes. The mortlity of the insects ws recorded t 24 or 48 h fter tretment. The insect mortlity t ech concentrtion of the insecticides ws corrected y the mortlity of the control sucrose solution ccording to Aott 1. Dt were sujected to proit nlysis for ech concentrtion-mortlity experiment 2 nd LC vlues were clculted. After 48 h, the insects were removed nd the weight of honeydew in ech vil ws determined using.1-mg sensitivity electronic lnce (ER-12A). The feeding rte (F) ws clculted s follows: F = W 1 -W 2 (where W 1 is the first weight nd W 2 is the reweighing fter desicction). The percentge of reduction in honeydew excretion ws clculted on the sis of control nd then converted into proit for clculting FI (% feeding inhiition concentrtion s ppm). Residul Period of Systemic Insecticides Applied s Seedling-Box Tretment One hundred grms of pre-germinted seed of Akitkomchi ws sown in seedling-ox (3 6 2.5 cm). The grnulr insecticides, imidcloprid (Admire 2% Grnulr) nd crtp (Pdn 4% Grnulr), were pplied to the seedling-ox prior to trnsplnting t the recommended rte for controlling GLH. The treted rice seedlings were trnsplnted into rice field with trnsplnting mchine. The control plnts were left untreted with insecticides. The experimentl plots (4 12 m) were immeditely surrounded y plstic
ScienceAsi 31 (25) 153 Tle 1. Toxicity of four systemic insecticides to dult mle GLH fter 48 h y prfilm method. Insecticide LC (ppm) Slope* Slope Slope imidcloprid.3.62.8.56.8 2.4 crtp 9.86 1.49 4.44 2.54 2.64 1.43 propphos 2.53.9 4.69.62.18 1.61 disulfoton 529.2.78 21.98.61.81.49 *Slope of regression line., nd represent GLH popultions collected from Tsuku, Tniym, nd Ntori respectively. to the lortory t 7 dy-intervls. Eight hills were smpled from ech plot. Only one tiller from ech hill ws selected for romocresol green-treted filter pper in plstic cup which ws minimlly modified from Pthk nd Heinrichs 14. Four tillers from ech hill were selected for the prfilm schet method 15 t 7 DAT. Plnts were infested with 5 newly emerged dult mles of GLH. The mortlity ws recorded fter 24 h nd 48 h nd the feeding rte ws recorded fter 24 h, t the regulted temperture. The feeding rte ws mesured y honeydew production re on filter pper treted with.4 w/v % romocresol green solution (Wko Pure Chemicl Industries, Ltd., Jpn) in the plstic cup t 7-63 DAT nd in prfilm schet t 7-84 DAT. The numers of lefhoppers in the treted plots were counted. Sticky ords (18 25 cm) were used to collect the insects from hills in ech treted plot. The dt ws nlyzed with ANOVA. % Mortlity % Feeding inhiition imidcloprid imidcloprid.1.1 1.1.1 1 crtp crtp.1 1.1 1 propphos propphos.1 1.1 1 disulfoton disulfoton.1 1.1 1 Log insecticide concentrtion (ppm) GLH- GLH- GLH- Fig 2. Concentrtion-mortlity nd -feeding rte reltionship in mle dult GLH. For, nd refer to Tle 1. Legends:
154 ScienceAsi 31 (25) RESULTS Concentrtion-Mortlity nd -Feeding Inhiition Biossys (Prfilm Method) Insecticide Susceptiility The LC vlues of imidcloprid, crtp, disulfoton nd popphos to GLH popultions re shown in Tle 1. There were lrge vritions etween LC vlues of insecticides in ech insect strin. The LC of most insecticides for the strin ws the smllest nd those for the strin ws significntly lrger thn tht for ll strins except the LC vlue of imidcloprid. The order of resistnce level of GLH to crtp, disulfoton nd popphos ws, >>, ut the order ws different for imidcloprid (Tle 1, Fig. 2). The LC vlues of disulfoton, propphos nd crtp for the strin were 6, 1, nd 3 times lrger thn for the strin, while those for the strin were 14, 2 nd 2 times lrger thn for the strin, respectively. The strin showed resistnce to propphos nd disulfoton (LC vlues 2 nd 529 ppm), while these insecticides remined effective for the strin (LC vlues.18 nd.81 ppm). From the prfilm method, imdcloprid ws shown to e more effective ginst four insect strins thn crtp, propphos or disulfoton. The insecticide susceptiilities to imidcloprid were not different etween ny of the insect strins. The LC of nd were 2 times lrger thn tht of. Imidcloprid chieved % corrected mortlity t the concentrtions 1.56,.78 nd 1.56 ppm for,, nd, respectively (Fig. 2). Feeding Inhiition The FI vlues of imidcloprid, crtp, disulfoton nd popphos to GLH re shown in Tle 2. Identiclly to the lethl concentrtions, the FI vlue for the strin ws significntly lrger thn those for ll strins except the FI vlue of imidcloprid. The FI vlues for were the smllest (Fig. 3). Though the LC vlue of propphos for ws lrger thn y 1, times, the FI vlues still remined similr to ech other t low concentrtions (5.4 nd 1.2 ppm). Tle 2. Feeding inhiition of four systemic insecticides in dult mle GLH fter 48 h y prfilm method. Insecticide FI (ppm) Slope* Slope Slope imidcloprid.2 1.8.3 1.23.1.35 crtp 2.728 1.11 1.849 1.31.675 3.64 propphos 5.434 1.28 4.873.87 1.224.42 disulfoton 93.188 1.59 35.184.61 9.966.81 *Slope of regression line., nd represent GLH popultions collected from Tsuku, Tniym, nd Ntori respectively. %Feeding inhiition nd mortlity 14 12 8 6 4 2.1.1 1 16 14 12 8 6 4 2.1.1 1 12 8 6 4 2.1.1 1 Log insecticide concentrtion (ppm) %Mortlity Fig 3. Reltionship etween %feeding inhiition nd mortlity of GLH treted with imidcloprid using the prfilm method., nd refer to Tle 1. Verticl rs indicte stndrd devition. Legends: %Mortlity The feeding rtes of, nd for imidcloprid were reduced to more thn 9% of the control t the concentrtions.2,.1 nd.1 ppm, respectively. This result indicted tht imidcloprid nd crtp showed chrcteristics s n ntifeednt for ll GLH strins, nd propphos nd disulfoton showed chrcteristics s n ntifeednt only for the strin. The LC /FI rtios of, nd colonies were c 15, 27 nd 8 for imidcloprid, while those for crtp were c 4, 2 nd 4 respectively. Reltionship etween the feeding inhiition nd mortlity The reltionship etween the feeding inhiition nd the mortlity curve of ech insect strin is shown in Figs. 3-6. According to this the feeding inhiition occurred t concentrtions sustntilly lower thn the lethl concentrtions, nd imidcloprid nd crtp showed pronounced chrcteristic s n ntifeednt
ScienceAsi 31 (25) 155 16 14 12 8 6 4 2.1.1 1 1 2 18 16 14 12 8 6 4 2.1.1 1 1 %Feeding inhiition nd mortlity 14 12 8 6 4 2.1.1 1 1 14 %Feeding inhiition nd mortlity 14 12 8 6 4 2.1 1 1 14 12 12 8 6 4 2.1.1 1 1 8 6 4 2.1 1 1 Log insecticide concentrtion (ppm) Log insecticide concentrtion (ppm) %Mortlity %Mortlity Fig 4. Reltionship etween %feeding inhiition nd mortlity of GLH nd treted with crtp using the prfilm method., nd refer to Tle 1. Verticl rs indicte stndrd devition. Legends: %Mortlity Fig 5. Reltionship etween %feeding inhiition nd mortlity of GLH nd treted with propphos using the prfilm method., nd refer to Tle 1. Verticl rs indicte stndrd devition. Legends: %Mortlity for ll GLH strins. The feeding inhiition of propphos occurred only for the strin ut it occurred t higher concentrtions thn imidcloprid or crtp. The corrected mortlity for the strin ws % t 2 ppm of propphos, ut the feeding rte ws reduced to % t 5.4 ppm. The ntifeednt chrcteristics of propphos on the nd strins were not ovious. In the strin, % reduction in feeding rte occurred t lower concentrtion thn the % corrected mortlity in imidcloprid nd crtp, ut not in propphos nd disulfoton t 48 h. For disulfoton, feeding inhiition occurred in t the high concentrtion (93 ppm). Identiclly to tht occurring in propphos, no ntifeednt chrcteristic occurred in or strins. Residul Period of the Systemic Insecticides Toxicity of Insecticides The toxicity of two systemic insecticides, imidcloprid (Admire grnule) nd crtp (Pdn grnule), to GLH, pplied in seedling-ox (g/ox; the recommended rte to control GLH) efore trnsplnting is presented in Fig. 7. Of the two insecticides, imidcloprid hd persistence ginst most insect strins, with more thn 8% mortlity during the first two weeks, while crtp ws less effective. With crtp the mortlity ws less thn 2%, even y the first week fter trnsplnting. The mortlity of most insect strins on imidcloprid-treted plnts dropped elow % t the heding stge. There ws no significnt correltion etween insect mortlity on crtp-treted plnts nd the dys fter tretment (DAT), ut significnt correltion ws recognized on imidclopridtreted plnts (Fig. 7). Effect of Insecticides on Feeding Rte Feeding rte s indicted y re of honeydew excretion on filter pper ws mesured nd nlyzed.
156 ScienceAsi 31 (25) %Feeding inhiition nd mortlity 14 12 8 6 4 2.1.1 1 1 12 8 6 4 2 1 1 2 18 16 14 12 8 6 4 2.1 1 1 Log insecticide concentrtion (ppm) %Mortlity Fig 6. Reltionship etween %feeding inhiition nd mortlity of GLH nd treted with disulfoton using the prfilm method., nd refer to Tle 1. Verticl rs indicte stndrd devition. Legends: %Mortlity On imidcloprid- nd crtp-treted plnts, the feeding rtes of most insect strins were lower thn those of the control. Increse in feeding rte ws slow on plnts treted with imidcloprid. A significnt correltion etween the feeding rte nd the DAT ws recognized in imidcloprid-treted plots for ll insect strins, ut ws not found in crtp-treted plots. Imidcloprid ws still ffecting the feeding rte of the insect until the flowering stge (8 DAT) (Fig. 7). - r =.53 - % Mortlity % Honeydew excretion r = -.71* r = -.85** r = -.68* Fig 7. Effects of two systemic insecticides, imidcloprid nd crtp, pplied in seedling-ox efore trnsplnting, on mortlity nd feeding rte of GLH., nd refer to Tle 1. Verticl rs indicte stndrd devition. Legends: imidcloprid crtp plot, indicting tht the insect popultions were reuilt in the crtp nd untreted plots. There ws no significnt difference in numer of GLH etween the crtp nd the untreted plots. Most of the insects found in the imidcloprid plot were dults. There were smll numer of nymphs in the imidcloprid plot (Fig.8). DISCUSSION r =.48 r = -.23-2 2 r =.46 r =.69* 2 r = -.59 Dys After Tretment (DAT) r =.28 Imidcloprid crtp r =.82** r =.53 Effect fect of Seedling-Box Appliction on Insect s Popultion in the Field We surveyed the popultion of the GLH in the experimentl field plots t 85 DAT using sticky ord. The smll rown plnthopper (Lodelphx stritellus), white cked plnthopper (Sogtell furcifer) nd GLH were found. The nymphl density of oth plnthopper nd GLH in the crtp plot nd the untreted plots were higher thn in the imidcloprid Better understnding of the effects of insecticides on insect pests nd the rice plnt my provide n insight into the evlution of effects of insecticides nd strtegies to control or mnge resistnt insect pests. Vrious methods hve een developed nd used to evlute the susceptiility of GLH to insecticides. Conventionl topicl ppliction or the AChE sensitivity method re widely used to evlute the toxicity of insecticides to GLH, ut there hve een few studies on
ScienceAsi 31 (25) 157 A B No. of insect/ hills 14 12 8 6 4 2 c Plnthopper Lefhopper 14 12 8 6 4 2 c PH-Nymph c PH-Adult GLH-Nymph GLH-Adult Control Imidcloprid crtp Fig 8. Popultion density of plnthoppers (PH) nd GLH (A) nd numer of nymphs nd dults of PH nd GLH (B) in the rice field plots t 85 dys fter trnsplnting. Vlues re expressed s mens±se. The rs with the sme letter re not significntly different (P>.5). Legends: Control Imidcloprid crtp how to evlute oth the feeding rte nd the toxicity of systemic insecticides. Bsed on the results of the prfilm method in this study, crtp ws effective for ll insect strins,,, nd. However, in field tests the mortlity nd honeydew excretion on rice plnts collected from crtp-treted plots were not different from the untreted plots even 1 or 2 weeks fter tretment. Becuse of the low effects of crtp (pplied t g of Pdn 4% grnulr per seedling-ox) residue on rice plnts, the feeding rte nd mortlity of the insects were not ffected, nd the GLH ws le to uild up their popultion in the crtp-treted plots. Imicloprid showed pronounced chrcteristics oth in mortlity nd feeding inhiition t low concentrtions for ll insect strins. The LC nd FI were smller thn crtp. 9% mortlity ws oserved for ll insect strins until 21 DAT nd imidcloprid lso cused reduction of feeding fter the lethl effect diminished. Like other insecticides in neonicotinoids clss, imidcloprid cts on the nervous system nd moleculr trget sites is the insect nicotinic cetylcholine receptor 21. The sulethl neurotoxicnt cn ffect insect ehviour. The effects of sulethl doses of the insecticide were occurred when insufficient molecules to cuse deth reched the sites of insecticidl ction 3. It my cts s feeding deterrent like the resistnt vriety interfering nutrient sorption from the plnt tissues. Becuse of the long persistence of imidcloprid in the soil, its hlf-life ws 17 dys-1 yer in US or 36-43 dys in Indi 3,17. At the recommended rte, 2g/h of imidcloprid y seedling-ox ppliction, the residue in rice plnt (.1 ppm) ws 65 DAT 7. The present study lso showed tht the residue effect of imidcloprid on the rice plnt could suppress the feeding ctivity of GLH nd this effectiveness remined until the flowering stge of Akitkomchi t TBIC. The LC vlues of propphos nd disulfoton for the strin collected from n intensively treted re in southern Jpn exceeded 2 nd ppm, respectively. The strin showed moderte resistnce to propphos nd disulfoton when compred with strin collected from less treted re in northern Jpn. The slopes of regression lines of propphos for (1.61) were twice s steep s those for (.9) nd (.62), ut for disulfoton the slopes of regression lines for the (.78) nd (.61) were higher thn those for (.49). However we found tht the feeding inhiitions of propphos nd disulfoton were strong with the OPs resistnce strin,, while it did not occur in nd strins. Antifeednt ctivity of systemic insecticides t sulethl doses hs een considered to e n importnt chrcteristic for protecting treted plnts from virus disese y suppression or interference of feeding of the vector insects. Feeding inhiition y systemic insecticide cn e evluted y the intersection point etween two curves, percentge mortlity nd percentge feeding inhiition, sed on those in control
158 ScienceAsi 31 (25) (Figs. 3-6). The intersection point indicted the property of systemic insecticide s n ntifeednt when tested y prfilm method. A low intersection point (where the feeding inhiition occurred t sulethl concentrtions) is considered to show strong ntifeednt chrcteristic. In contrst, n insecticide giving higher intersection point (the feeding inhiition occurs t or higher thn lethl concentrtions) is considered to give no feeding inhiitory ction 11. When we consider ntifeednt ctivity of some insecticides s strtegy for preventing virus diseses, we should e creful out the negtive function of the insecticides t sulethl concentrtion. Sulethl doses of some insecticides cn stimulte reproductive ctivity of insect pests or increse the susceptiility of plnts to insects 16,2. With this considertion in mind, we hve to e concerned out the effect of the insecticide residue on the rice plnt on the insects fter tretment, especilly when insecticide is pplied to seedling-ox efore trnsplnting. ACKNOWLEDGMENTS This work ws supported y the Tsuku Interntionl Centre (TBIC), nd the Jpn Interntionl Coopertion Agency (JICA). REFERENCES 1. Aott WS (1925) A method of computing the effectiveness of n insecticide. J Econ Entomol 18, 265-7. 2. Bliss CI (1935) The clcultion of the dosge-mortlity curve. Ann Appl Biol 22, 919-24. 3. Cox C (21) Insecticide fctsheet: Imidcloprid. J Pestic Reform 21, 15-21. 4. Hm H nd Iwt T (1971) Insensitive cholinesterse in the Nkgwr strin of the green rice lefhopper, Nephotettix cincticeps Uhler (Hemipter: Cicdellide), s cuse of resistnce to crmte insecticides. Appl Entomol Zool 6, 183-91. 5. Hyshi M nd Hykw M (1962) Mlthion tolernce in Nephotettix cincticeps Uhler. Appl Entomol Zool 6, 2-2. 6. Hiino H nd Cungn RC (1986) Rice tungro-ssocited viruses nd their reltions to host plnts nd vector lefhoppers. Trop Agr Res Ser 19, 173-82. 7. Iwy K (1993) Admire nd pest control. Noyku Kenkyu 39, 3-6. 8. Kto Y, Nomur M nd Miyt T (1999) Negtively correlted cross-resistnce etween N-Methyl crmte nd monocrotophos in green rice lefhopper, Nephotettix cincticeps Uhler. J Pestic Sci 24, 368-9. 9. Kono Y, Ngrshi D nd Ski M (1975) Effects of crtp, chlordimeform nd dizinon on the proing frequency of green lefhopper (Hemipter: Deltocephlide). Appl Entomol Zool 1, 58-6. 1. Miyt T, Ski H nd Sito T (1981) Mechnism of joint toxic ction of Kitzin P with mlthion in the mlthion resistnce green rice lefhopper, Nephotettix cincticeps Uhler (Hemipter: Deltocephlide). Appl Entomol Zool 16, 258-63. 11. Ngt T nd Hykw T (1998) Antifeeding ctivity of conitic cid nd oxlic cid on rown plnthopper, Nilprvt lugens (Stål) nd green rice lefhopper, Nephotettix cincticeps (Uhler). Jpn J Appl Entomol Zool 42, 115-21. 12. Nomur M, Kto Y nd Miyt T (1999) Monitoring of orgnophosphte nd crmte resistnce nd identifying comintion of insecticides showing negtively correlted cross resistnce in the green rice lefhopper (Nephotettix cincticeps Uhler) (Hemipter: Deltocephlide). Appl Entomol Zool 34, 525-3. 13. Ozki K (1966) Some notes on the resistnce to mlthion nd methyl prthion of the green lefhopper, Nephotettix cincticeps Uhler (Homopter: Cicdellide). Appl Entomol Zool 1, 189-96. 14. Pthk PK nd Heinrichs EA (1982) Bromocresol green indictor for mesuring feeding ctivity of Nilprvt lugens on rice vrieties. Philipp Entomol 5, 195-8. 15. Pthk PK, Sxen RC nd Heinrichs EA (1982) Prfilm schet for mesuring honeydew excretion y Nilprvt lugens. J Econ Entomol 75, 194-5. 16. Reissig WH, Heinrichs EA nd Vlenci SL (1982) Insecticideinduced resurgence of the rown plnthopper, Nilprvt lugens, on rice vrieties with different levels of resistnce. Environ Entomol 11, 165-8. 17. Srkr MA, Roy S, Kole RK nd Chowdhury A (21) Persistence nd metolism of imidcloprid in different soils of West Bengl. Pest Mng Sci 57, 598-62. 18. Sogw K (1971) Preliminry ssy of ntifeeding chemicls for rown plnthopper, Nilprvt lugens (Stål) (Hemipter: Delphcide). Appl Entomol Zool 6, 215-8. 19. Widirt IN, Hermwn W, Oy S, Nkjim S nd Nksuji F (1997) Antifeednt ctivity of Androgrphis pnicult (Acnthcee) ginst the green rice lefhopper, Nephotettix cincticeps (Hemipter: Cicdellide). Appl Entomol Zool 32, 561-6. 2. Wu J, Xu J, Yun S, Liu J, Jing Y nd Xu J (21) Pesticideinduced susceptiility of rice to rown plnthopper Nilprvt lugens. Entomol Exp Appl, 119-26. 21. Zhng A,Kyser H, Mienfisch P nd Csid JE (2) Insect nicotinic cetylcholine receptor: conserved neonicotinoid specificity of [3H]imidcloprid inding site. J Neurochem 75, 1294-33.