Tolerance to Cypermethrin and Endosulfan in Field Populations Of

Home , Cypermethrin

INSECTICIDERESISTANCEANDRESISTANCEMANAGEMENT . Tolerance to Cypermethrin and Endosulfan ill Field Populations of the Bollworm (Lepidoptera: Noctuidae) from Texas

L.H.B. KANGA,l F. W. PLAPP, JR.,2 B. F. McCUTCHEN,3 R. D. BAGWELL,4 AND J. D. LOPEZ, JR.5

Department of Entomology, Texas A&M University, College Station, TX 77843-2475 Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021

J. Econ. Entomol. 89(3): 583-589 (1996) ABSTRACT Responses to insecticides in bollworm, Helicoverpa zea (Boddie), males collected from 1988 to 1994 in sex-pheromone baited traps in the Brazos Valley near College Station, TX, varied during each season with tolerance being highest in midseason. Significant tolerance occurred with cypermethrin in 1988 and 1989, and with endosulfan in 1994. Tests in 1994 with profenofos or methomyl showed no significant tolerance to these insecticides. \Ve found significant variations between trap sites in responses of field bollworms to cypermethrin, suggesting that increased tolerance may be a localized phenomenon. Tests with cypermethrin plus piperonyl butoxide indicated significant synergism in bollworms collected from the field, suggesting that enhanced metabolic degradation may be a factor in pyrethroid tolerance in this species. Diagnostic concentrations for monitoring tolerance in field-collected bollworm males were determined for all insecticides tested. The results reported here validate use of the adult vial test to monitor for tolerance to insecticides in the bollworm, and provide information useful for the development of a resistance management strategy intended to ex- tend the efficacy of insecticides used to control the bollworm.

KEY WORDS Helicoverpa zea, insecticide tolerance monitoring, pyrethroid tolerance, endosulfan tolerance

COST EFFECTIVECONTROLof heliothine species Allen et al. 1987; Luttrell et aI. 1987; Plapp et al. has been a major concern in cotton production. 1987, 1990; Elzen et al. 1992; Kanga and Plapp The bollworm, Helicoverpa zea (Boddie), is an 1992; Kanga et al. 1993; Graves et al. 1994). A economically important pest of corn and cotton pyrethroid resistance management strategy for the and sometimes of sorghum, soybeans, and alfalfa tobacco budworm was developed and implement- in the United States. Control is usually achieved ed in many areas of the cotton belt. This strategy with insecticides. Bollworm first developed resis- is based on avoiding pyrethroid use early in the tance to organophosphorus and organochlorine in- season so that the high infestations of tobacco bud- secticides (Wolfenbarger 1971, Sparks 1981). More worm in midseason can be controlled with pyre- recently, tolerance to pyrethroid insecticides was throids. reported in field bollworm (Stadelbacher et al. Bollworm infestations frequently occur in com- 1990, Hsu and Yu 1991). Low level resistance to bination with infestations of tobacco budworm. In- pyrethroids, 5 to la-fold, was clearly shown by secticide rates required to control budworm are Abd-EIghafar et al. (1993) in tests of bollworm col- generally higher than those required for bollworm lected in southeast Arkansas and Illinois. control. These use rates may exert intense selec- Resistance to pyrethroid, organophosphorus, tion pressure on bollworm populations, Therefore, carbamate, and cyclodiene insecticides in the to- the potential for development of resistance in the bacco budworm, Heliothis virescens (F.), has been bollworm presents a very serious threat to the to- widely documented (Plapp and Campanhola 1986; bacco budworm resistance management strategy. A successful resistance management strategy de- ICurrent address: Dt'partment of Entomolo!(Y, University or Ar- pends in part on monitoring responses of cotton izona, Tucson, AZ 85721. pests to the various insecticides used in cotton pro- 2Current addrt,ss: A~rkulture Canada, Vineland Station, ON LOR 2EO Canada. duction, Monitoring should detect changes in sen- ~Currt'nt address: DuPont A~ Products, Stine-Haskell Research sitivity which may occur during the cotton growing Ct'ntt'r. P. O. Box 30, Nt'wark, DE 19714. season. Thus, monitoring can assist in conserving 'Cum'nt address: Macon Ridgc Station, Louisiana State Uni- available major types of insecticides in a resistance vt'rsity, 212 Macon Ridge Road, Winnsboro, LA 71295. :iU.S. Dt'partnll'nt of Agriculture, Agricultoral Hesearch Ser- management program and help avert field control vict', Collt'gt' Station. TX 77840. failures. In this study, we report results of moni-

Table l. Responses (LC ± confidence intervals) of susceptible (8) and field collected (F-year) bollworm males to cypermethrin in 1988, 1989, and 1993

TRc Strain nO Slope:!: SE LCsob LCoob r LCso LCoo Sd 1081 0.84:!: 0.23 0.05 0.57 0.44 (0.01-0.09) (0.29-1.02) F-1988e 3166 0.89:!: 0.97 0.17 1.92 3.40 3.37 0.42 (0.13-0.26) (1.45-2.84) (1.58- 5.90) (1.95-4.66) F-198if 3051 1.59:!: 0.92 0.44 2.77 8.8 4.9 0.34 (0.39-0.49) (2.43-3.25) (5.9-11.21) (3.27- 7.34) F-1993f 750 1.03:!: 0.46 0.09 1.59 1.8 2.9 0.27 (0.04-0.15) (0.5lh3.81) (0.36- 3.84) (0.71-11.6) Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021

o Number of bollworm males tested. Data from multiple <:allections were pooled. b Concentrations are expressed in micrograms of insecticide per vial. C Tolerance ratio (TR) calculated by dividing the LCso or LCoo for the field strain by the LCso or LCoo for the laboratory susceptible strain. d Insects collected in June and September 1988 when insecticide susceptibility was high. e Insects collected in May. July, and August 1988. f Insects collected from May to September. toring bollworm populations for tolerance to sev- tained in 1993 and1994 from the Southern Field eral insecticides in the Brazos Valley near College Crop Insect Management Laboratory, USDA- Station, TX. We also suggest diagnostic concentra- ARS, Stoneville, MS, where the insects have been tions of insecticides for use in resistance monitor- reared on artificial diet for many generations with- ing. out intentional insecticide exposure. For cypermethrin bioassays, we used data obtained with June and September 1988 field-collected bollworm Materials Wid Methods males as a susceptible strain, because insects col- Insecticides. All insecticides were technical lected these months were more sensitive to insec- grade materials (>90% purity) and used as sup- ticides than individuals collected at other times. plied by the manufacturer. We used cypermethrin Insecticide Bioassays. Male bollworms were (FMC, Princeton, NJ), endosulfan (FMC, Phila- removed from pheromone traps and brought to delphia, PA), profenofos (Ciba, Greensboro, NC), the laboratory where they were fed overnight with methomyl (Dupont, Wilmington, DE) and the syn- a cotton pad soaked in 10% sugar water. Moths ergist piperonyl butoxide (PBO) (90%; Fairfield were placed individually in 20-ml glass scintillation American, Frenchtown, NJ). vials coated with a film of insecticide (Plapp et al. Insects. During the cotton growing seasons, col- 1987, Kanga and Plapp 1992). Vials treated with lections of bollworm males from pheromone traps acetone only were used as controls. Vials contain- were made weekly during May, June, July, August, ing moths were held at room temperature (25°C) and September within a 16-km radius in the Braz- and mortality was determined after 24 h exposure. os Valley near Snook, TX, 20 km west of College Adults that were unable to fly a short distance (> 1 Station. A susceptible strain of bollworm was ob- m) when tossed into the air were considered to be

Table 2. Responses (LC ± confidence interval) of laboratory susceptible (8) and field collected bollworm males (field) to different insecticides in 1994

Insect- TRC Strain "a Slope:!: SE LCsob LCoob r icide LCso LC90 Endosulfan S 200 3.29 :!: 1.68 0.27 0.84 6.52 (0.13-0.55) (0.41- 1.68) Field 957 2.07:!: 0.14 0.84 3.45 3.11 4.10 4.19 (0.66-1.02) (2.79- 4.53) (2.74-3.96) (2.74-8.14) Profenofos S 154 6.13 :!: 1.53 4.42 7.15 6.36 (1.41-8.48) (4.43-25.4) Field 792 3.31:!: 0.23 2.52 6.14 0.57 0.86 9.17 (1.76-3.26) (4.6 -10.17) (0.45-0.73) (0.58-1.29) Methomyl S 167 0.18 :!:0.62 0.51 1.23 5.12 (0.16-0.98) (0.50-- 3.13) Field 754 0.15:!: 0.49 0.30 0.94 0.59 0.76 10.65 (0.14-0.43) (0.65- 2.20) (0.46-0.75) (0.51-1.14)

a Number of bollworm males tested. Data from different experiments were pooled. b Con(.'entrations are expressed in microgrdms of insecticide per vial.

C Tolerance ratio (TR) calculated by dividing the LCso or LCoo for the field str.un by the LCso or LCoo for the laboratory susceptible strain. JIIn(' ] 996 KANGA ET AL.: INSECTICIDE TOLERANCE IN BOLLWORMS 58,'5

Tahl" 3. Toxidty of "YI."rlnethrin with or without PRO (500 j.tg per viol) to lahoratory susceptihle Dml field boUworm mol"s coU"cted from Snook, TX, in September, 1993

Cypermethrin alone Cypermethrin with PBO SR" Strains LCso LCso n" Slope:!: SEM nil Slope:!: SEM (95% CI) (95% CIl" (95% CIl" S 98 1.06:!: 0.29 0.07 95 1.09 :!:0.99 0.05 1.40 (0.03-0.10) (0.03-0.08) (1.00-1.78) Fit-ld 153 1.03 :!:0.22 0.17 102 1.07:!: 0.29 0.06 2.83 (0.12--n.26) (0.03-0.09) (2.22--3.60) TRd 2.43 1.20 (95% Cl) (1.91-J.ll) (0.94-1.53)

" Numlwr of tohacco bollworms tested. Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021 " 95% eonndenet> limits shown lJt'neath each LCso. r Sy,wrgism ratio (SR) ca\culated hy dividin~ the LCso for cypermethrin alone hy the LC50 for cypermethrin with PBO. ,J Tolerance ratio (TR) calculated by dividin~ the LC50 for ReId strain by the LC50 for susceptible strain. sllsceptible. From 1988 to 1994, we tested multi- the general linear models procedure of SAS (SAS ple field populations of bollworm to determine the Institute 1985). patterns of responses to insecticides and to estab- lish diagnostic concentrations for use in tolerance Results monitoring. We tested piperonyl butoxide (PBO) as a met- Response of Bollworm to Insecticides. Tests abolic synergist for cypermethrin with susceptible with bollworm males collected in pheromone traps and field strains of bollworm. The amount of PBO in May, July, and August 1988 and from May to used (500 /Lgper vial) was the highest concentra- September 1989 demonstrated significant toler- tion that did not cause any symptoms of poisoning ance to cypermethrin compared with bollworm or mortality during the experimental period. Two males collected in June and September 1988 (Ta- groups of insects were tested at each time. Insects ble 1). Tolerance ratios were 3.4- and 8.8-fold at from the first group were placed individually inside the LCso level in 1988 and 1989, respectively. Tol- glass vials coated with a residual film of synergist erance declined to <2-fold in bollworm males test- for 1 h; those from the 2nd group were placed ed in 1993; this difference was not significant. individually in control vials treated with acetone BoJ]worm males collected in June through Sep- only. After 1 h, both groups of insects were trans- tember 1994 were significantly more tolerant to ferred to vials containing residues of cypermethrin. endosulfan compared with the laboratory strain The experiment was replicated at least 10 times. from Mississippi (Table 2). In contrast, field-col- Statistical Analyses. Concentration-mortality lected bollworm were more susceptible to profen- data were analyzed by probit analysis (Russell et ofos and methomyl than the laboratory strain. The al. 1977). Control mortality was never >5%; data tolerance ratios at the LC.50 and LC90 were 3.1- were corrected for control mortality using Abbott's and 4.1-fold for endosulfan, 0.57- and 0.86-fold for (1925) formula. Data from multiple experiments profenofos, and 0.59- and 0.76-fold for methomyl. were pooled before analyses to capture natural Synergism by Piperonyl Butoxide. Results of variation (Robertson et al. 1995). Differences bioassays of cypermethrin with or without PBO on among populations in responses to insecticides the laboratory susceptible strain and bollworms were considered not significant if the 95% confi- collected in September 1994 had a significant tol- dence interval of the tolerance ratio at the LCso erance ratio of 2.4-fo]d compared with cypermeth- level bracketed 1.0 (Robertson and Preisler 1992). rin alone (Table 3). In contrast, tolerance to cy- Percentage mortality values were arcsine trans- permethrin with PBO in the field strain (tolerance formed and anal)""i:edby a genera] linear models ratio = 1.2) was not statistically different from 1.0. procedure (SAS Institute 1985). Untransferred val- Data indicated a l.4-fold increase in toxicity of cy- ues are presented for clarity. Data on the resis- permethrin to susceptible bollworms pretreated tmlce distribution experiment were tested using with PBO and a statistically significant 2.8-fold in-

TabI., 4. Rt,spol1lleby month of field eoUeeted boUworm moles from Snook, TX, exposed to cypermethrin in 1989

F values by month and treatment Trt>atmt'nt May June July August September

COllen 20.88· 49.84· SUS" 68.51" 11.23" Tmp location 1.96NS O.73NS 2.28" 3.0" 2.08NS

For ("Olwt'ntration df = 3, for trap location df = 8. F tests were conducted using ~enerallinear models procedure [SAS Institute 19115].• , Si/-,'"incant(P < 0.05), NS, not significant. 586 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 89, no. 3

100 50 --0- 0.5 fI8Ivia1 1 fI8Ivia1 A 40-- 2.SfI8Ivia1 80

20 10 o

JUNE JULY AUG SEPT Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021 MAY JUNE JULY AUG SEPT MONTH MONnl

100 70 --0- 0.5 fI8Ivia1 - IfI8Ivia1 B 80 _ B 60_ 2.5J1ll/via1 Ip.g/viaJ. 2.SJLg/Yiai 50 - 5 fI8Ivia1 10 fI8Ivia1 : 40 - ~ 30

" 20 20

10 o JUNE JULY AUG SEPT MAY JUNE JULY AUG SEPT MONTH MONTII

80_ 50 --0- 0.5 fI8Ivia1 c - IfI8Ivia1 40 - 2.5 fI8Ivia1 c 60_- .l - < ...> ~ 40 :::> tit'" 20 • ... 10 - • JUNE JULY AUG SEPT o MAY JUNE JULY AUG SEPT MONTH MONnl Fig. 2. Percentage of survival of field bollworm males exposed to different insecticides in 1994; A, endosulfan; Fig. 1. Percentage of survival of field bollworm males B, profenofos; C, methomyl. exposed to different concentrations of cypermethrin: A, 1988; B, 1989; C, 1993.

= 8, 12; P < 0.007), by month (F = 4.93; df = 4, crease in toxicity for field bollworms pretreated 12; P < 0.006), and to trap-month interaction (F with PBO. These results suggest that enhanced = 1.56; df = 8, 28; P < 0.05). The interaction metabolism may be a component of pyrethroid tol- between month and concentration was not signif- erance in the bollworm. icant (F = 1.61; df = 12, 28; P > 0.05). Responses Response of BoUworm by Trap Location. of bollworm to each concentration were signifi- Analyses of 1989 data on responses of field col- cantly different throughout the season, e,g., the re- lected moths to cypermethrin (Table 4) indicated sponse was dose-dependent (Table 4), Percentage significant differences in response to cypermethrin survival by trap location fluctuated during the sea- between concentrations (F = 124.41; df = 3, 12; son. In May, June, and September, we found no P < 0.001), among individual traps (F = 3.45; df significant differences in percentage survival be- June 1996 KANGA ET AL.: INSECTICIDE TOLEHANCE IN BOLLWOHMS 587

• --0- Susceptible - F..Jd1988 - Fieldl989 A 7 - Fieldl993 --0-- Susceptible - Field

:;; o 0:

4 1.5 .1 '.5 1.5 10 100 Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021

Cyperrn.thrln (1'8/vlll) Pror.nofo. (1'./vlll)

Swccptible Field

:iso 0: 5

4 .1 1.5 It Itt 10

Endosul'.n (J1i',,'al) Melhornyl (I'alvlal) Fill:.3. Hesponsesof pooled field populations of bollworm males and a laboratory susceptible strain exposed to different concentrations of several insecticides. Arrows represent proposed concentrations for tolerance monitoring: A, cypermethrin; B, endosulfan; C, profenofos; D, methomyl. tween locations (i.e., there was no statistical dif- moths collected at other times during the season. ference in levels of pyrethroid tolerance within the Tests with methomyl yielded similar results (Fig. 16-km radius being sampled). However, significant 2C). As with profenofos, data were less variable by differences in percentage of survival between lo- month than with cypermethrin or endosulfan, in- cations were found in July and August, suggesting dicating no increase in tolerance to the insecticide that tolerance to cypermethrin in the bollworm during the Season. may be a highly localized phenomenon. Diagnostic Concentrations for Tolerance Field Monitoring. Percentage of survival of Monitoring. Based on the responses described multiple collections of male bollworms tested with above, we attempted to determine optimum con- cypermethrin in 1988, 1989, and 1993 and then centrations for monitoring adult bollworm toler- exposed to different concentrations of cypermeth- ance to the different insecticides tested. Data for rin is shown in Fig. 1. Analyses of results by month field collected bollworm males treated with each indicated that tolerance to cypermethrin in 1988 insecticide were pooled and compared with re- (Fig. lA) declined from May to June, increased in sponses in susceptible populations. Data with cy- July and August, and declined again in September. permethrin (Fig. 3A) indicated that concentrations In 1989, tolerance of bollworm to cypermethrin of 0.5, 1, and 2.5 J.Lg per vial of cypermethrin are was higher all season th,m in 1988 (Fig. IB). In satisfactory for tolerance monitoring in the boll- 1993, patterns of response to cypermethrin were worm. Responses to endosulfan of laboratory and similar to those in 1988. The level of tolerance was field collected bollworm males (Fig. 3B) suggested much lower than in 1989 (Fig. lC). that concentrations of 1, 2.5, and 5 J.Lg per vial are Survival of multiple collections of male boll- satisfactory for tolerance monitoring. Responses to worms made in 1994 and exposed to different con- profenofos (Fig. 3C) suggested concentrations of centrations of 3 insecticides is shown in Fig. 2. Tol- 2.5, 5, and 10 J.Lg per vial are ideal for monitoring erance to endosulfan increased in midseason tolerance. We propose use of 0.25, 0.5, and 1 /-tg (July-August) and declined in September (Fig. 2A). per vial concentrations for tolerance monitoring to Tolerance to profenofos varied little by month methomyl (Fig. 3D). These concentrations were (Fig. 2B), indicating a lack of buildup of tolerance chosen because they maximize differences in re- during the season. That is, moths collected in July sponses of susceptible and tolerant bollworms to and August were only slightly more tolerant than the insecticides tested. At 2.5 /-tg per vial cyper- 588 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 89, no. 3 methrin, 5 P,g per vial endosulfan, 10 p,g per vial Thus, under present agronomic conditions control profenofos, and 2.5 p,g per vial methomyl, all sus- problems with bollworms are not a serious threat ceptible bollworms will be killed, whereas some to cotton production in Texas. resistant individuals will survive. If only 1 concentration is to be used for each insecticide, these are Acknowledgments probably optimal. We thank D. L. Bull (USDA-ARS, College Station, TX) for reviewing the manuscript. We express our grati- Discussion hIde to C. Hubbard (USDA-ARS, College Station, TX) for assistance in making bollworm collections. We also Our data indicated that significant tolerance to thank, E.M.M. Gardiner for technical assistance. cypermethrin was present in field populations of

bollworm from Texas in 1988 and 1989, but not in Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021 1993. Our data agree with the earlier report of References Cited Abd-Elghafar et al. (1993) on pyrethroid resistance Abbott, W. S. 1925. A method of computing the ef- in Arkansas and Illinois, and suggest that low level fectiveness of an insecticide. J. Econ. Entomol. 18: resistance or tolerance to pyrethroids in the boll- 265-267. worm may be widespread. In our study, pyrethroid Abd-Elghafar, S. F., C. O. Knowles, and M. L. Wall. tolerance decreased at the end of each season. 1993. Pyrethroid resistance in two field strains of These decreases may result from dilution through Helicoverpa ::;ea (Lepidoptera: Noctuidae). J. Econ. interbreeding with susceptible individuals, lower Entomol. 86: 1651-1655. Allen, C. T., W. L. Muller, R. R. Minzcnrnayer, and fitness in tolerant individuals, or reduced repro- J. S. Armstrong. 1987. Development of pyrethroid ductive success as was seen with the tobacco bud- resistance in Heliothis populations in cotton in Texas, worm (Campanhola et al. 1991). Based on these pp. 332-335. In Proceedings Beltwide Cotton Pro- results, development of economically important duction and Research Conferences, National Cotton levels of resistance to cypermethrin in the boll- Council of America, Memphis, TN. worm seems unlikely to occur under current agri- Campanhola, C., and F. W. Plapl), Jr. 1989. Toxicity cultural conditions in Texas. These results may be and synergism of insecticides against susceptible and contrasted with the tobacco budworm, in which pyrethroid resistant neonate larvae and adults of the tolerance has increased steadily from 1986 through tobacco budworm (Lepidoptera: Noctuidae). J. Econ. Entomol. 82: 1527-1533. 1993 (Graves et al. 1994). Campanhola, C., B. F. McCutcben, E. R. Baehrecke, The synergism of cypermethrin by PBO sug- and F. W. Plapp, Jr. 1991. Biological constraints gested enhanced metabolism may be a component associated with resistance to pyrethroids in the tohac- of pyrethroid tolerance in the bollworm. The pre- co budworm (Lepidoptera: Noctuidae). J. Econ. En- dominance of target site resistance to pyrethroid tomol. 84: 1404-1411. in the tobacco budworm (Campanhola and Plapp Elzen, G. W., B. R. Leonard, J. B. Graves, E. Burris, 1989, McCaffery et al. 1989) and the presence of and S. Micinski. 1992. Resistance to pyrethroid, metabolic resistance in Helicoverpa arrnigera Hub- carbamate, and organophosphate insecticides in field ner) (Forrester 1989) suggested that resistance in populations of tobacco budworm (Lepidoptera: Noc- tuidae) in 1990. Econ. Entomol. 85: 2064-2072. the bollwonn may be more closely related to re- J. Forrester, N. 1989. Countermeasures for pyrethroid sistance in H. than to resistance in the arrnigera resistance. Part I: synergists. Aust. Cotton Grower 10: tobacco budworm. 58-61. The variability from trap to trap in cypermethrin Graves, J. B., B. R. Leonard, E. Burris, S. Micinski, tolerance seen in 1989 illustrates the necessity to S. R. Martin, C. A. White, and J. L. Baldwin. perform monitoring at multiple loci. Clearly, data 1994. Status of insecticide resistance in tobacco bud- based on a small number of trap sites may not worm and bollworm in Louisiana, pp. 769-774. In provide an accurate estimate of resistance prob- Proceedings BeItwide Cotton Production and Re- lems in a particular area. The pattern of responses search Conferences, National Cotton Council of America, Memphis, TN. to endosulfan observed in 1994 were very similar Rsu, E. L. and S. J. ¥u. 1991. Insecticide resistance to those observed earlier with cypermethrin. Tol- in the com eaTWorm, Heliothis::;ea (Boddie). Resistant erance in the bollworm to endosulfan, coupled Pest Management 3: 18. with the absence of tolerance to profenofos and Kanga, L.R.B., and F. W. Plapp, Jr. 1992. Devel- methomyl, suggests that organophosphorus and opment of a glass vial technique for monitoring resis- carbamate insecticides may be more useful than tance to organophosphate and carbamate insecticides endosulfan for managing bollworm populations. in the tobacco budworm and the boll weevil, pp. 731- Overall, our results suggest that tolerance to in- 734. In Proceedings Beltwide Cotton Production and secticides is already present in the bollworm, but Research Conferences, National Cotton Council of America, Memphis, TN. only at low frequencies. Tolerance does not appear Kanga, L.R.B., F. W. Plapp. Jr., M. L. Wall, and G. to be a serious problem because of the decline that W. Elzen. 1993. Monitoring for resistance to non- occurs at the end of each season. Apparently, the pyrethroid insecticides in the tobacco budworm, vol. cost of tolerance to insecticides in the bollworm is 2, pp. 802-807. In Proceedings Beltwide Cotton Pro- sufficiently severe that tolerance frequencies de- duction and Research Conferences, National Cotton crease rapidly when selection pressure is removed. Council of America, Memphis, TN. June 1996 KANGA ET AL.: INSECTICIDE TOLERANCE IN BOLLWORMS 589

Luttrell, R. G., R. T. Roush, A. Ali, J. S. Mink, M. R. Tabashnik [eds.], Pesticide resistance in arthropods. Reid, and G. L. Snodgrass. 1987. Pyrethroid re- Chapman & Hall, New York. sistlIDce in field populations of Heliothis virescem Robertson, J. L., and H. K. Preisler. 1992. Pesticide (Lepidoptera: Noctuidae) in Mississippi in 1986. J. bioassays with arthropods. CRC, Boca Raton, FL. Econ. Entomol. 80: 985-989. Robertson, J. L., H. K. Preisler, S. S. Ng, L. A. Hi- McCaffery, A. R., E. J. Little, R. T. Gladwell, G. T. ckle, and W. D. GeIerntcr. 1995. Natural varia- Holloway, and C. H. Walker. 1989. Detection and tion: A complicating factor in bioassays with chemical mechanisms of resistance in Heliothis virescens, pp. and microbial pesticides. J. Econ. Entomol. 88: 1-10. Russell, R. M., J. L. Robertson, and N. E. Savin. 207-211. In Proceedings Beltwide Cotton Production 1977. POLO: a new computer program for probit and Research Conferences, National Cotton Council analysis. Bull. Entomol. Soc. Am. 23: 209-213. of America, Memphis, TN. SAS Institute. 1985. SAS users' guide: statistics, ver- Plapp, F. W., Jr., and C. Campanhola. 1986. Syner- sion 5. SAS Institute, Cary, NC. gism of pyrethroid by chlordimeform against suscep- Sparks, T. C. 1981. Development of insecticide resis- Downloaded from https://academic.oup.com/jee/article/89/3/583/2216363 by guest on 01 October 2021 tible and resistant Heliothis, pp. 167-169. In Proceed- tance in Heliothis zea and Heliothis virescens in North ings Beltwide Cotton Production and Research America. Bull Entomol. Soc. Am. 27: 186-192. Conferences, National Cotton Council of America, Stadelbacher, E. A., G. L. Snodgrass, and G. W. EI- Memphis, TN. zen. 1990. Resistance to cypermethrin in first gen- Plapp, F. W. Jr., G. M. McWhorter, and W. H. Vance. eration adult bollworm and tobacco budworm (Lepi- 1987. Monitoring for resistance in the tobacco bud- doptera: Noctuidae) populations collected as larvae on worm in Texas in 1986, pp. 324-326. In Proceedings wild geranium, and the second and third larval gen- Beltwide Cotton Production and Research Confer- erations. J. Econ. Entomol. 83: 1207-1210. ences, National Cotton Council of America, Memphis, Wolfenbarger, D. A., M. J. Lukefahr, and H. M. Gra- TN. ham. 1971. A field population of bollworms resis- Plapp, F. W. Jr., C. Campanhola, R. D. Bagwell, and tant to methyl parathion. J. Econ. Entomol. 64: 755- B. F. McCutchen. 1990. Management of pyre- 756. throid-resistant tobacco budworms on cotton in the Received for publication 13 March 1995; accepted 1 United States, pp. 237-260. In R. T. Roush and B. E. December 1995.