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Subtropical Plant Science, 55: 18-21.2003 Response of Field-Collected Strains of Tobacco Budworm
(Lepidoptera: Noctuidae) to Permethrin in the
Lower Rio Grande Valley, TX, USA and Across Mexico
J. L. Martinez-Carrillo1 and D. A. Wolfenbarger2
1CIRNO-INIFAP, Apartado Postal #515, Ote. Col. Campestre, Cd. Obregon, Sonora, Mexico 85760 255 Calle Cenizo, Brownsville, TX 78520 ABSTRACT
LD50 values of permethrin for 32 strains of tobacco budworm, Heliothis virescens (F.) collected from cotton and
tomatoes in Mexico, and the Lower Rio Grande Valley, TX, (LRGV) in the United States of America, (USA) from 1981 to
1982 and 1990 to 1996 ranged from 0.0088 to 0.9 µg/larva. A resistance threshold of >0.2 µg permethrin/larva was proposed.
Most (72%) of the strains were susceptible to permethrin. The threshold resistance was exceeded from 1989 to 1991 in
northwestern Mexico and in 1992 in north central Mexico. In Valle del Yaqui, Sonora, populations of strains exceeded the
resistant threshold from 1989 to 1990 and then reverted to susceptibility from 1991 to 1996.
Los valores de DL50 de permetrina para 32 cepas del gusano de la yema del tabaco, Heliothis virescens ( F ), colectadas
en algodón y en tomate en México y en el Bajo Valle del Río Grande (LRGV), Texas en Estados Unidos (E.U.) de 1981 a 1982
y de 1990 a 1996 variaron de 0.0088 a 0.9 µg/larva. Se propuso un umbral de resistencia de 0.2 µg de permetrina/larva. La
mayoría de las cepas (72%) fueron susceptibles a la permetrina. El umbral de resistencia fue sobrepasado de 1989 a 1991
en el noroeste de México y en el 1992 en el área norte del centro de México. En el Valle del Yaqui, Sonora, las poblaciones
de las cepas sobrepasaron el umbral de resistencia de 1989 a 1990 volviéndose de nuevo susceptibles de 1991 a 1996.
Key Words: Insecticides, resistance When laboratory evaluations show that LD50s of an susceptibility to permethrin was elucidated from data shown insecticide have increased after application in cotton fields here and the literature from four locations in Sonora and Baja over a period of time and continue to increase it is suspected that resistance to that insecticide has developed. Permethrinhas been used on cotton by producers for control of the tobacco MATERIALS AND METHODS
budworm, Heliothis virescens (F.) in the Lower Rio GrandeValley, Texas and Mexico since 1974 [Davis et al. 1975, Technical permethrin (93%) was obtained from FMC Wolfenbarger et al. 1977 and 1984 and Wolfenbarger and Harding 1982]. No resistance to permethrin had been reported Insect collections: Ten to 30 eggs and larvae of the test
in northeastern Mexico or the LRGV, TX (Wolfenbarger et al.
insects were collected from cotton in the LRGV of TX (USA) 1984). In 1987 the tobacco budworm showed resistance to this and northeastern, north central and northwestern Mexico from insecticide in northwestern Mexico [Martinez-Carrillo et al.
1981 to 1998 [Table 1]. Insects were collected from a field nearest the indicated town in the north central and northeastern With published information on response of strains to Mexico and the LRGV of TX and delivered to the laboratory at permethrin and the results reported here we wanted to propose Brownsville or Weslaco, TX, USA. At each location in a resistance threshold for this pest on cotton in the LRGV of Caborca, Hermosilla, Guaymas and Valle del Yaqui, Sonora, TX and northwestern, north central and northeastern Mexico.
and Mexicali, Baja California eggs or larvae were collected The resistance threshold is an arbitrarily selected LD50 which from three fields of cotton or tomato, Lycopersicum separates resistant from susceptible populations. Using this esculentum Mill. [Martinez-Carrillo 1991). threshold, resistance, susceptibility and reversion to Eggs and larvae were reared to pupation on artificial diet susceptibility were determined for each strain. Reversion to [Shaver & Raulston 1971) at 27± 2º C, 60 to 80% rh and 12:12 Subtropical Plant Science, 55: 18-21.2003 h of light : dark [Raulston and Lingren 1972). As moths generation one for an LD50 value and the strain was discarded emerged, 5 to 15 pairs were placed in a 3.78 L cardboard or enough larvae were treated in generation two to complete the container and fed 5% sugar-water. Each additional 15 pairs LD50 from both generations. Totals of larvae for each dose from were placed in another container and handled similarly. Cloth both generations were used to determine the LD50.
covers that provided oviposition sites were changed daily and Topical treatments.
held in sealed 336 g paper cups until eggs hatched. Upon maintained in technical grade acetone. Three to 10 doses, as eclosion neonate larvae were placed singly on artificial diet in µg/larva, of 0.000059, 0.00048, 0.00096, 0.0076, 0.015, 0.031, 30 ml cups with cardboard caps and held for testing.
0.62, 0.12, 0.24, 0.48 0.96 and 1.92 permethrin were used to When possible all strains were treated with permethrin treat all available third stage larvae of each strain each day with within one generation. We either treated enough larvae in procedures for the topical application technique (Anonymous Table 1. Toxicity of permethrin to larvae of the tobacco budworm collected from cotton in Mexico and the Lower Rio Grande
Valley, TX, 1981-1982, and 1989-1996.
Subtropical Plant Science, 55: 18-21.2003 1970). When larvae on the diet were 3 to 7 d old and weighed Using this threshold 72% of the strains were susceptible. 22 ± 6 mg (from 16 to 28 mg) they were treated using a micro- The range of number of larvae tested and percentage of applicator (ISCO, Inc., Lincoln, NE). First d of fourth stage strains within the range were <100=9%, 101-200=25%, weigh 30 to 32 mg. Each day of treating was considered to be 201-300=47%, 301-400=13% and 401-700 = 6%.
a replicate and, depending on availability, 4 to 100 larvae/dose Percentages of larvae used for each strain treated followed a were treated in each replicate. Larvae of different strains grew at different rates so different numbers of larvae were treated in Slopes of regressions showed 22%, <1, 75% >1.1 to 2 and each replicate. Larvae were weighed daily within the range of 3%, >2. The flatter slopes are considered to have more factors weights indicated. Larvae that weighed <16 mg were discarded after eight d. Mortalities were taken after 48 h. Larvae were Northwestern and North Central Mexico. In 1981, LD50
considered dead when they did not respond when probed with values of 11 collections ranged from 0.0088 (Valle de Yaqui, Sonora,) to 0.12 µg/larva (Felipe Carrillo Puerto, Michoacan], LD50 values, the 95% confidence interval (CI) as µg/larva a 15 fold difference. Five LD50 values were determined for and slope ± standard error (SE) were determined by [SAS strains collected from Torreon, Caborca, Guaymas, and 1988). Total number of larvae treated and total number killed Mexicali, Mexico: all strains were susceptible.
by each dose in both generations were used in the statistical LD50 values exceeded the resistance threshold from 1987- analysis. LD50 values with overlapping CI values were not 1993 in Valle del Yaqui, 1987-1988 in Hermosilla, 1985-1988 significantly different. If the “t” at P <0.05 for the ratio of in Caborca, and 1986-1989 in Mexicali (Martinez-Carrillo slope/SE was <1.96 the regression was not significant and did 199l). Six to nine years after resistance was determined, there not differ from 0. Results were summarized by insecticide.
was reversion to susceptibility to permethrin in Valle del Yaqui LD50 values were ranked from highest to lowest each year from 1994 to 1996 (Table 1) as there was in 1984-1985, 1985- 1986 and 1985 in populations in Mexicali, Hermosillo and The combination of the three strains from northwestern Caborca, respectively (Martinez-Carrillo 1991). Mexico allowed a large supply of larvae for treating in the first In Valle del Yaqui in 1990 and 1991 LD50 values of generation. Control larvae to determine natural mortality were permethrin determined at the beginning of the season (Table 1) not needed nor used in these combined collections. Larvae of and at the end of the season were not significantly different.
this species from field collections rarely die from natural All four populations were resistant. Populations were also causes. Control larvae were used for three of the single field resistant to permethrin in 1992 and 1993. Then there was a collections in generation two from northeastern Mexico and reversion to susceptibility by the populations sampled from the LRGV, USA because a few neonate to second stage larvae died from natural causes in generation one. When control In 1992 the LD50 value of 0.9 µg permethrin/larva from a larvae were not used 0.0000059 µg/larva was used because it collection from Torreon, Coahuila, was the greatest of the 32 does not kill >1%. The standard for maximum mortalities of values determined (Table 1). After a decade of use in 1991 and untreated control larvae is 10%. Following treatment and mortality determinations, survivors were pooled and reared to Northeastern Mexico and LRGV, TX, USA. In 1981
three strains from the LRGV, TX were susceptible topermethrin (Table 1). In 1982 a collection from Estacion Cuauhtemoc, Tamaulipas, was susceptible. In 1991-1992 collections from LRGV in Rio Bravo, LD50 values (32) of permethrin with significant Tamaulipas, Mexico, were susceptible (Table 1). The regressions ranged from 0.0088 to 0.9, a 102 fold difference collections from Estacion Cuauhtemoc in 1991 and 1994 in the (Table 1). The frequency distribution of LD50 values of 0.0088 tropical area of northeastern Mexico exhibited resistance to to 0.03, 0.031 to 0.099, 0.1 to 0.19 and >0.20 µg/larva were permethrin (Teran- Vargas 1994). In 1992 a strain from field 4, 25%, 22%, 25% and 28%, respectively. LD50 values were La Blanca, TX, LRGV, was resistant to permethrin. That same equally distributed over the 100 fold range. Factors for year three strains collected from three other fields near La response were equally distributed among the strains in both Blanca were susceptible. There were more resistant strains to permethrin in the early 1990s than in the early 1980s in the Field control data was shown by Wolfenbarger and Harding (1982) using permethrin in field plots against the In 1987 and 1993 LD50 values of 0.89 and 3.83 µg tobacco budworm from the LRGV. At 0.11 kg(AI)/ha, in 1977 permethrin/larva, respectively, were shown in Uvalde, TX and 1981, percentage control was 39% and 48% while in 1978 (USA), in the Winter Garden area 400 km north of the LRGV and 1979 percentage control was 70% and 87%, respectively.
[Sparks et al. 1988 and Wolfenbarger and Vargas-Camplis No trend for control or the failure to control populations was 1997). Both strains were resistant to permethrin. These LD50 shown in the four years the field tests were conducted. LD50s values are in contrast to our results. If all our LD50 values were were not determined from any collection from any of these similar to those in the Winter Garden area all of the strains plots. A review of all LD50 values found in the literature for Mexico and the LRGV, TX and the results shown here suggests Resistance to permethrin was more prevalent by the strains a proposed resistance threshold of >0.2 µg/larva for this insect.
of this insect in the Winter Garden area, northwestern Mexico, Subtropical Plant Science, 55: 18-21.2003 northeastern Mexico and the LRGV. An LD50 of permethrin in Obregon, Sonora, Mexico (retired) and J. Vargas-Campos, north central Mexico exhibited resistance in 1992, but the LD50 INAFAP, Campo Agricola Experimental, Rio Bravo, Tamaulipas Mexico, for sending or bringing egg and larval Natural mortalities of all larvae of the tobacco budworms collections to Brownsville or Weslaco, TX. in all collections prior to treatment are minimal for neonatethrough second stage larvae. None of the collections exceeded REFERENCES CITED
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Martinez-Carrillo, J. L. 1991. Montoreo de Resistance a Untreated controls were not needed to estimate natural piretroides en gusano tablacero, Heliothis virescens, en el mortalities for these 32 field collections.
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(Dugger, P. and D. Richter). Cotton Insect Research and In the 1990s >95% of the cotton in Mexico was planted in Control Conference, Nashville, TN. National Cotton subtropical and temperate areas. In the 1990s no cotton was planted in western Mexico. Heterogeneity for response to Wolfenbarger, D. A., J. A. Harding and J. W. Davis, Jr. 1977.
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dichloroethenyl)-2, 2-dimethylcyclopropanecarboxylate Numerous mechanisms for resistance factors can be offered for against boll weevils and tobacco budworms. J. Econ.
this insect, but the variation in these factors from insect to Wolfenbarger, D. A. and J. A. Harding. 1982. Effects of pyrethroid insecticides on certain insects associated with ACKNOWLEDGMENTS
Wolfenbarger, D. A., J. A. Harding and S. H. Robinson. 1984.
Thanks are extended to J. R. Raulston, USDA-ARS.
Tobacco budworm (Lepidoptera: Noctuidae): Variation in Weslaco, TX (retired); R. Bujanos-Muniz, INAFAP, Campo response to methyl parathion and permethrin in the Agricola Experimental, Celaya, Guanajuato, Mexico; A. P.
subtropics. J. Econ. Entomol. 77: 701-703.
Teran-Vargas, INAFAP, Campo Agricola Experimental, Wolfenbarger, D. A. and J. Vargas-Camplis. 1997. Tobacco Estacion Cuauhtemoc, Tamaulipas, Mexico; J. N. Norman, Jr., budworm: response to pyrethroid insecticides in the Winter Texas Agriculture Extension Service, Weslaco TX; L. Guerra- Garden area and in the Lower Rio Grande Valley.
Sobravilla, INAFAP, Campo Agricola Experimental, Cuidad Resistant Pest Management Newsletter. 9:39-42.

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