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 85760255 Calle Cenizo, Brownsville, TX 78520ABSTRACT 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
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
10% in any of the collections. Control larvae were not used inthe first generation of the single larvae collection from Rio
Anonymous. 1970. Standard method of detection of insecticide
Bravo, Tamaulipas in 1981 and San Perlita and La Blanca,
resistance in Heliothis zea (Boddie) and H. virescens (F.).
LRGV in 1982 when five to 11 larvae in each collection did not
Bull. Entomol. Soc. Amer. 16: 147-149.
grow to 16 mg. In generation two 15 to 28 larvae from each of
Davis, J. W., Jr., J. A. Harding and D. A. Wolfenbarger. 1975.
the strains were used as controls. One to three percent of the
Activity of a synthetic pyrethroid against cotton insects. J.
larvae of each collection died. The low dose of 0.0000059
µg/larva killed 0 to 3% in each replicate for each strain.
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.
noreste de Mexico. Southw. Entomol. Suppl. No. 15:59-67.
Raulston, J. R. and P. D. Lingren. 1972. Methods for Large-
Scale Rearing of the Tobacco Budworm. U. S. Dept. Agric,Agriculture Research Service. Production Research
The Tropic of Cancer divides the tropical cotton producing
areas in southern Tamaulipas and western Mexico from the
SAS Technical Report. 1988. Additional SAS/STAT Procedures
subtropical and temperate cotton producing areas in northern
P-179. Release 6.03. SAS Institute, Cary, NC. 252 pp.
Mexico. Northern Tamaulipas includes cotton grown along and
Shaver, T. N. and J. R. Raulston. 1971. A soybean-wheat germ
within 25 km of the Rio Grande River, the LRGV of Mexico.
diet and rearing the tobacco budworm. J. Econ. Entomol.
The subtropical producing areas are planted in February-March.
The tropical areas are planted in June-July. Insect collections
Teran-Vargas, A. P. 1996. Insecticide resistance of tobacco
were made in all these areas. LD50 values were not determined
budworm in southern Tamaulipas, Mexico. 784-785. In
each year for each strain because they were not available.
(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.
permethrin is shown with these regressions. It was a natural
Isomers of (3-phenoxyphenyl) methyl (±)cis, trans-3-(2, 2-
occurrence in collections for all the locations identified here.
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
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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Early the next morning, a plumber’s truck parked near the Pitzker Antiquities shop. The driver was a man in overalls and a painter’s cap. He climbed out of the cab, a wrench in his hand, and “Hi, Marta,” he said. “Are they open?” “Not yet.” Also dressed in worker’s overalls, she was staring through a small telescope that she had pressed against the wall of the truck. “Oh,