Chemical control of white grub Liogenys fuscus (Blanchard 1851) (Coleoptera: Melolonthidae) in cornfields

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1 Received: 1/I/27 Accepted: 29/II/28 Pulished:11/V/28 Aville online t: CHEMICAL CONTROL Chemicl control of white gru Liogenys fuscus (Blnchrd 1851) (Coleopter: Melolonthide) in cornfields ANTÔNIO C. SANTOS 1, ADENEY F. BUENO 2, REGIANE C. O. F. BUENO 3 E SIMONE S. VIEIRA 4 1 Dow AgroSciences Industril Ltd, São Pulo, SP. E-mil: csntos1@dow.com 2 Current ddress: Emrp Soj, Londrin, PR. E-mil: deney@cnpso.emrp.r 3 Escol Superior de Agricultur Luiz de Queiroz ESALQ/USP, Pircic, SP. E-mil: rcdolive@eslq.usp.r 4 Centro Federl de Ensino Tecnológico, CEFET, Rio Verde, GO. BioAssy 3:5 (28) Controle químico do coró Liogenys fuscus (Blnchrd 1851) (Coleopter: Melolonthide) n cultur do milho RESUMO Prgs de solo como o complexo de corós são de grnde importânci ns culturs de milho e soj em váris regiões produtors do Brsil, sendo que Liogenys fuscus (Blnchrd) é espécie mis comum n região Centro- Oeste. Os produtores de milho têm utilizdo inseticids pr controle desss prgs iniciis; entretnto, pouco se conhece sore eficiênci dos diferentes inseticids no controle de L. fuscus. Sendo ssim, o ojetivo do presente trlho foi vlir eficiênci de lguns inseticids, plicdos no solo no sulco de plntio ou em trtmento de sementes, pr o mnejo de L. fuscus n cultur do milho no Estdo de Goiás, durnte s sfrs de 24/25 e 25/26. Durnte sfr 24/25, os trtmentos testdos form clorpirifós 45, 675, 9 e 117 g.h -1, endosulfn 525 g.h -1, fipronil 16 g.h -1 plicdos no sulco de plntio e durnte sfr 25/26 os trtmentos form clorpirifós 45 e 675 g.h -1, fipronil 16 g.h -1 plicdos no sulco de plntio e tmém fipronil 37,5 e 5 g.1 kg de sementes -1 e timetoxm 7 g.1 kg sementes -1 em trtmento de sementes. Os resultdos mostrrm que: clorpirifós (45, g.h -1 ) pulverizdo no sulco de plntio foi suficiente pr o controle de L. fuscus, oservndo-se um estnde de té sete vezes mior e um tmnho de plnt de proximdmente dus vezes mior em relção o trtmento testemunh n sfr 24/25 devido o tque d prg. Resultdos semelhntes form otidos com fipronil (16, g.h -1 ) tmém plicdo no sulco de plntio sendo que mos form superiores o endosulfm n dose de 525, g.h -1 nest sfr. Já n sfr 25/26 não se oservou incremento o tmnho de plnt e estnde devido à plicção dos inseticids, sendo que s plnts não presentrm sintoms de tque d prg. Ness sfr os resultdos presentdos pelos trtmentos de sementes (fipronil 37,5 e 5 g.1 kg de sementes -1 e timetoxm 7 g.1 kg de sementes -1 ) tmém form similres o clorpirifós e fipronil n plicção relizd no sulco de plntio, podendo, portnto ser considerd um outr opção de controle químico pr o mnejo dess prg. Sendo ssim clorpirifós e fipronil plicdos no sulco de plntio lém de fipronil e timetoxm plicdos em trtmento de semente podem ser lterntivs de controle químico de L. fuscus n cultur de milho em condições semelhntes o encontrdo nesses experimentos. PALAVRAS-CHAVE Ze mys L., clorpirifós, endosulfm, fipronil, timetoxm, prgs de solo. ABSTRACT Soil pests such s the white gru complex re of gret importnce in different Brzilin regions, nd Liogenys fuscus (Blnchrd) is the most common species t the Brzilin Western Centrl Region. Corn producers hd lrgely relied on pesticides to keep initil pest outreks under control, however, there is little informtion regrding the efficcy of different insecticides to control L. fuscus. The ojective of this reserch ws to evlute the effectiveness of some insecticides, pplied either to the soil or the seed, in controlling L. fuscus in cornfields in Stte of Goiás during two crop sesons. In 24/25 seson the following chemicls were pplied in furrow: chlorpyrifos (45, 675, 9, nd 117 g.h -1 ); endosulfn (525 g.h -1 ); nd fipronil (16 g.h -1 ). During the 25/26 seson the tretments were chlorpyrifos (45 nd 675 g.h -1 ), fipronil (16 g.h -1 ), oth pplied in furrow, s well s fipronil (37.5 nd 5 g.1 kg of seeds -1 ) nd thimethoxn (7 g.1 kg of seeds -1 ) pplied s seed tretment. The results showed tht chlorpyrifos (45. g.h -1 ) in furrow ws effective to control L. fuscus. Plnt stnd nd plnt size in this tretment were 7-fold nd 2-fold tller thn plnts in the control plots, during the 24/25 seson. Similrly, fipronil 16. g.h -1 pplied in furrow hd positive results, oth outperforming endosulfn 525. g.h -1 in furrow ppliction. However, during the 25/26 seson there ws no enefit regrding plnt stnd or plnt size due to insecticide Sociedde Entomológic do Brsil 1

2 Chemicl control of white gru Liogenys fuscus Sntos et l. ppliction, nd no pest injury ws oserved in the plnts. During this crop seson, results recorded for the seed tretment (fipronil 37.5 nd 5 g.1 kg of seeds -1 nd thimethoxn 7 g.1 kg of seeds -1 ) were lso similr to the chlorpyrifos nd fipronil in furrow tretment, which my e considered to e used s chemicl control procedure. Therefore, under conditions similr to those prevlent during the execution of these trils, in furrow ppliction of chlorpyrifos nd fipronil s well s seed tretment with fipronil nd thimethoxn my e used to control L. fuscus outreks in cornfields. KEYWORDS Ze mys L., chlorpyrifos, endosulfn, fipronil, thimethoxm, soil pests. The occurrence of soil pests hs een incresingly importnt to grin producers in Brzil. Among them, there re severl species of white grus (Cruz et l. 1999) tht cn e devstting griculturl pests y feeding on crop roots often cusing plnt deth or severe injury nd impiring full hrvest potentil. These pests used to e of secondry importnce, however the doption of no-tillge crop mngement with n intensive use of chemicls hs fvored their occurrence nd serious outreks hve occurred, mostly in corn nd soyen fields (Grssen 1993, Vin et l. 21). Moreover, lrvl infesttions re gretly influenced y soil type or texture (Morón 24) nd firous-rooted plnts, such s corn, re susceptile wheres stronger tp-rooted plnts re often more tolernt to injury. There re severl white gru species of economic importnce in Brzil (Oliveir et l. 24). Phyllophg cuyn (Moser) hs een commonly reported dmging different crops roots in Brzil (Oliveir et l. 1992, Oliveir 1997). In the Stte of Rio Grnde do Sul, Phyllophg triticophg (Morón & Slvdori) nd Dilooderus derus (Sturm) hve dmged not only corn ut lso soyens nd whet (Silv 1995, Slvdori 2). In Goiás, species commonly ssocited with crop roots hve een Liogenys fuscus (Blnchrd) (Coleopter: Melolonthide), dmging soyens, corn, nd sorghum (Cost et l. 24). L. fuscus outreks clerly ffected soyen nd corn production in Goiás in 22 nd 23 minly t Edéi nd Leopoldo de Bulhões towns. Economic losses however were not precisely quntified. As well s other pests, such s the stink ugs, white gru outreks might lso e more severe for mize sown off-seson since the popultion increses nd the insects develop during the seson (Wquil et l. 24). Fields plnted erlier (Septemer, Octoer) re less dmged y white grus thn lte sown fields (Decemer) (Oliveir et l. 24). There re different wys of suppressing soil pest popultions using chemicl nd iologicl techniques (Pedigo 22). However, there is not sufficient informtion regrding the efficcy of chemicl control of white grus, minly ecuse these pests used to e of secondry importnce nd lso ecuse reserch works ddressing their control usully require intensive lor nd re difficult to e crried out. Also, informtion out insecticide efficcy over these pests is insufficient, especilly regrding L. fuscus which presents higher incidence in the Western Centrl Region. Growers usully rely on chemicl control only, ut they lso hve een testing different insecticides t different rtes nd methods, ut due to the lck of stndrdized methodology very few results were otined so fr. Therefore, informtion regrding these spects is crucil to provide efficient control of L. fuscus outreks. This reserch ws crried out to evlute some insecticides pplied in furrow nd s seed tretment in order to control L. fuscus popultion in corn fields. Mteril nd Methods Two field trils were conducted in corn fields locted in Edéi, GO, Brzil from 24 to 26. The insecticides tested were chlorpyrifos, endosulfn, fipronil nd thimethoxn. The experiments were crried out in conventionl corn crop mngement. Infesttion ws oserved during n evlution done the dy efore insecticide ppliction. The experimentl design ws Rndomized Complete Block (RCB) with 4 replictions. The first experiment ws sowed in Decemer, 24 with the folllowing thretments: (1) chlorpyrifos 45 g.h -1 (Sre 45 EW, Dow AgroSciences Industril Ltd); (2) chlorpyrifos 675 g.h -1 (Sre 45 EW, Dow AgroSciences Industril Ltd); (3) chlorpyrifos 9 g.h - 1 (Sre 45 EW; Dow AgroSciences Industril Ltd); (4) chlorpyrifos 117 g.h -1 (Sre 45 EW, Dow AgroSciences Industril Ltd); (5) endosulfn 525 g.h -1 (Thiodn 35 CE, Byer CropSciences Ltd); (6) fipronil 16 g.h -1 (Regente 8WG, Bsf S.A.); 7. Control (wter). All tretments were pplied in furrow ove the seed using ckpck CO 2 spryer with constnt pressure. The equipment ws set to deliver 5 L.h -1 similrly to the usul procedure prcticed y frmers. The second experiment ws sowed t Octoer/25 with the folllowing tretments: (1) chlorpyrifos 45 g.h -1 (Sre 45 EW, Dow AgroSciences Industril Ltd); (2) chlorpyrifos 675 g.h - 1 (Sre 45 EW, Dow AgroSciences Industril Ltd); (3) friponil 16 g.h -1 (Regente 8WG, Bsf S.A.); (4) fipronil 37.5 g.1 kg of seeds -1 (Stndk 25 EC, Bsf S.A.); (5) fipronil 5. g.1 kg of seeds -1 (Stndk Sociedde Entomológic do Brsil 2

3 BioAssy 3:5 (28) 25 EC, Bsf S.A.); (6) thimethoxn 7. g.1 kg of seeds -1 (Cruiser 7WS, Syngent Proteção de Cultivos Ltd); (7) Control (wter). Furrow ppliction ws performed s descried for the first experiment. Seed tretment ws ccomplished pplying the insecticides inside plstic g nd using 5 ml of mixture.1 kg of seeds -1. In ll trils, seeds were sowed y hnd, providing good precision regrding the numer of seeds used per plot (5 seeds/meter). Trils were evluted t 45 nd 26 dys fter sowing for the first (24/25 seson) nd second tril (25/26 seson), respectively. Ech evlution ws done in hole 2 cm deep y 2 cm wide, dug long one meter of the centrl plnting row of ech plot (1. x.2 x.2 m), nd crefully serching the removed soil to detect the presence nd count L. fuscus lrve. Before sowing, pre-scouting ws rndomly done t 1 points selected inside field tril res. In ddition to white gru counting, the numer of plnts nd size of 2 plnts/plot were recorded to evlute plnt injury cused y insect feeding. Dt were sujected to ANOVA nd tretment mens were seprted y Tukey test (α = 5%). Results nd Discussion In the first tril, pre-counting smples inside plots found 3 ± 4 nymphs of L. fuscus.meter -1 (.4 m 3 of soil). Becuse tril ws instlled lte in seson (lte Decemer, 24), the mjority of these nymphs were of 3 rd instr. Nymphs t this stge s well s t lter instrs hve greter dmge potentil (Oliveir et l. 24) nd might hve cused the oserved significnt reduction in plnt stnd on control plots (98% of reduction) (Figure 1B). The fct tht white grus re ctive in the soil looking for food, my explin the presence of very few white grus in the control plots t 45 dys fter sowing. Control plots presented very few corn plnts (Figure 1B) with injured root systems tht cused reduced plnt size (Figure 1C). Consequently, due to the lck of food in the control plots, white grus nymphs present in these res might hve migrted to the surrounding plots. Control plots with higher pest infesttion thn treted plots were lso reported y Ceccon et l. (24), suggesting tht the evlution should e conducted previously. Considering tht est time for evlution is still unknown, it might e necessry to test severl periods fter sowing in future experiments. Due to the lck of white grus in the control plot t 45 dys fter plnting, ANOVA ws run only for the insecticide tretments to seprte tretment effects. Results showed tht chlorpyrifos (ll tested rtes) nd fipronil (16 g.h -1 ) were the est tretments outperforming endosulfn (525 g.h -1 ) in furrow ppliction (Figure 1A). Recording plnt numer nd mesuring plnts height might lso e helpful to evlute control efficcy. Tking the numer nd size of plnts into considertion, ll insecticide tretments differed from control ut did not differ mong themselves. Endosulfn (525 g.h -1 ) ws numericlly the worst tretment in oth plnt stnd (Figure 1B) nd plnt size (Figure 1C). Therefore, endosulfn ws in generl the worst in furrow tretment showing the highest numer of white grus (Figure 1A) nd numericlly the lowest plnt stnd nd plnt size mong ll insecticides tested (Figures 1B nd 1C). According to Myo (1986), insecticide efficcy trils for soil pests usully seprte excellent controlling insecticides from low control ones. However, it is not n esy tsk to seprte insecticides with intermedite control levels which might e the cse for endosulfn on this experiment. In the second tril (25/26 seson), precounting smples inside plots found 2 ± 2 nymphs of L. fuscus.meter -1 (.4 m 3 of soil). Becuse tril ws instlled erly in seson (erly Octoer, 25), the mjority of these nymphs were of 1 st or 2 nd instr. Nymphs from erly instrs re sometimes not dmging to plnts tht tolerte some root injury. Usully when crops re sowed erly in the seson (Septemer, Octoer), white grus do not cuse s much dmge s it is seen on crops sowed lte in the seson (Decemer) (Oliveir et l. 24). This is possile explntion why insecticide tretments did not sttisticlly differ from control for oth plnt stnd (Figure 2B) nd plnt size (Figure 2C). Other fctors might lso explin differences found in oth trils. There re other importnt fctors tht interfere on insect outreks such s soil humidity, how deep the insects re in the soil, nd soil temperture, mong others. Differences in these prmeters not controlled in oth trils might lso e responsile for differences in these results. It hs een reported tht soil insects re very difficult to control nd results re sometimes not consistent mong sesons due to still unknown resons (Bueno et l. 27). In the second tril, endosulfn ws not tested ecuse of poor performnce found in the first experiment (Figures 1A, 1B, nd 1C), nd seed tretment ws included. Evluting the results nd oserving tht the insect popultion ws composed mostly y nymphs t erly stges, fipronil (37.5 g nd 5 g.1 kg of seeds -1 ) nd thimethoxn (7 g.1 kg of seeds -1 ) were similr to furrow ppliction (Figures 2A, 2B nd 2C) nd should e considered s promising chemicl options to control L. fuscus outreks. Furrow ppliction of chlorpyrifos nd fipronil, s well s fipronil nd thimethoxn pplied s seed tretment cn e effective lterntives to control L. fuscus outreks t cornfields in the conditions this study ws conducted. Sociedde Entomológic do Brsil 3

4 Chemicl control of white gru Liogenys fuscus Sntos et l. White grus/4 cm 3 of soil A Chlorpyrifos 45 grms/h (in furrow) Chlorpyrifos 675 grms/h (in furrow) Chlorpyrifos 9 grms/h (in furrow) Chlorpyrifos 117 grms/h (in furrow) Endosulfn 525 grms/h (in furrow) Fipronil 16 grms/h (in furrow) Plnt stnd / 5 liner meters B Chlorpyrifos 45 grms/h (in furrow) Chlorpyrifos 675 grms/h (in furrow) Chlorpyrifos 9 grms/h (in furrow) Chlorpyrifos 117 grms/h (in furrow) Endosulfn 525 grms/h (in furrow) Fipronil 16 grms/h (in furrow) Untreted Plnt verge size (meter) Chlorpyrifos 45 grms/h (in furrow) Chlorpyrifos 675 grms/h (in furrow) C Chlorpyrifos 9 grms/h (in furrow) Chlorpyrifos 117 grms/h (in furrow) Endosulfn 525 grms/h (in furrow) Fipronil 16 grms/h (in furrow) Untreted Figure 1. Results on Liogenys fuscus control t 45 dys fter sowing. (A) Men ± SE of L. fuscus nymphs / smple (4 cm 3 ). (B) Men ± SE of plnts in 5 meter of row. (C) Men ± SE of plnt size (m). Mens followed y the sme letter re sttisticlly similr to ech other ccordingly to Tukey s test (α=.5). Edéi, GO, 24/25. Sociedde Entomológic do Brsil 4

5 BioAssy 3:5 (28) White grus/4 cm 3 of soil Plnt stnd / 5 liner meters Chlorpyrifos 45 grms/h (in furrow) Chlorpyrifos 675 grms/h (in furrow) Chlorpyrifos 45 grms/h (in furrow) A Chlorpyrifos 675 grms/h (in furrow) Plnt verge size (meter) B Fipronil 16 grms/h (in furrow) Fipronil 16 grms/h (in furrow) C Chlorpyrifos 45 grms/h (in furrow) Chlorpyrifos 675 grms/h (in furrow) Fipronil 37.5 grms/1kg of seeds Fipronil 5 grms/1kg of seeds Thimethoxn 7 grms/1kg of seeds Figure 2. Results on Liogenys fuscus control t 26 dys fter plnting. (A) Men ± SE of L. fuscus nymphs / smple (4 cm 3 ). (B) Men ± SE of plnts in 5 meter of row. (C) Men ± SE of plnt size (m). Mens followed y the sme letter re sttisticlly similr to ech other ccordingly to Tukey s test (α=.5). Edéi, GO, 25/26. Fipronil 37.5 grms/1kg of seeds Fipronil 16 grms/h (in furrow) Fipronil 5 grms/1kg of seeds Fipronil 37.5 grms/1kg of seeds Thimethoxn 7 grms/1kg of seeds Fipronil 5 grms/1kg of seeds Thimethoxn 7 grms/1kg of seeds Untreted Untreted Sociedde Entomológic do Brsil 5

6 Chemicl control of white gru Liogenys fuscus Sntos et l. References Cited Bueno, A. F., J. Nunes Jr. & L.J. Oliveir. 27. Avlição de inseticids e enxofre no controle de percevejo cstnho e de corós n cultur d soj, p In XXIX Reunião de Pesquis de Soj d Região Centrl do Brsil, Cmpo Grnde, MS, 225p. Ceccon, G., A. Rg, A.P. Durte & R.C. Siloto. 24. Efeito de inseticids n semedur sore prgs iniciis e produtividde de milho sfrinh em plntio direto. Brgnti, 63: Cost, R. B., P.M. Fernndes, M.A Morón, L.J Oliveir, E.A. Silv & R.G. Brros. 24. Bioecologi de corós no sistem de sucessão soj-milho sfrinh, p In O.F. Sriv (ed.). Resultdos de pesquis d EMBRAPA Soj-23: Entomologi. Londrin (n. 245), 56p. Cruz, I, P.A. Vin & J.M. Wguil Mnejo ds prgs iniciis de milho medinte o trtmento de sementes com inseticids sistêmicos. Sete Lgos (EMBRAPA-CNPMS, Circulr Técnic, 31), 39p. Grssen, D. N Corós ssocidos o sistem plntio direto. p In EMBRAPA Centro Ncionl de Pesquis de Trigo (Psso Fundo, RS). Plntio direto no Brsil. Psso Fundo: Aldei Norte/EMBRAPA-CNPT/FUNDACEP FECOTRI- GO/Fundção ABC, 166p. Myo, Z. B Field evlution of insecticide for control of lrve of corn rootworms, p In J.L. Krysn & T.A. Miller. (eds.). Methods for the study pest Dirotic. New York: Springer-Verlg, 26p. Morón, M. A. 24. Insetos de Solo, p In J.R. Slvdori, C.J. Ávil & M.T.B. Silv (eds), Prgs de Solo no Brsil. Psso Fundo, RS, 541p. Oliveir, L. J Ecologi comportmentl e de interções com plnts hospedeirs em Phyllophg cuyn (Moser) (Coleopter: Melolonthide, Melolonthine) e implicções pr seu mnejo n cultur d soj. Tese de doutordo, Instituto de Biologi, Universidde Estdul de Cmpins (UNICAMP), Cmpins, 148p. Oliveir, L. J., B. Sntos & J.R.P. Prr. 24. Corósd-soj, p In J.R. Slvdori, C.J. Ávil & M.T.B. Silv (eds), Prgs de Solo no Brsil. Psso Fundo, RS, 541p. Oliveir, L. J., B. Sntos & L.B. Amrl Coró pequeno d Soj. Londrin: Emrp Soj (Emrp Soj documentos, 51). 4p. Pedigo, L. P. 22. Entomology nd pest mngement. 4th edition. Person Eduction, Inc., Upper Sddle River, New Jersey. 742p. Slvdori, J. R. 2. Coró do trigo. (Emrp Trigo, Documentos, 17) Psso Fundo: Emrp Trigo. 56p. Silv, M. T. B Aspectos iológicos e dnos de Dilooderus derus Sturm, 1826 (Coleopter: Melolonthide) em plntio direto. Dissertção de mestrdo, Escol de Agronomi, Universidde Federl de Snt Mri, Snt Mri, RS, 76p. Vin, P. A., I. Cruz, L.J Oliveir & B.S. Corrê- Ferreir. 21. Mnejo de prgs em grossistem so plntio direto, p In Informe gropecuário Plntio direto n. 22. Wquil, J.M., C.J. Ávil, P.A. Vin, F.H. Vlicente & I. Cruz. 24. Ocorrênci e controle de prgs n cultur do milho no Mto Grosso do Sul Sfrinh. Sete Lgos (EMBRAPA-CNPMS, Circulr Técnic, 46). 12 p. Sociedde Entomológic do Brsil 6