Gw. Elzen, CHANGES IN RESISTANCE TO INSECTICIDES IN TOBACCO BUDWORM (LEPIDOPTERA, NOCTUIDAE) POPULATIONS IN MISSISSIPPI, 1993-1995, The Southwestern entomologist, 22(1), 1997, pp. 61-72
Strains of the tobacco budworm, Heliothis virescens (F.), collected in
Mississippi in 1993 through 1995 were evaluated in bioassays to four
classes of insecticides and Bacillus thuringiensis Berliner. High freq
uencies of resistance were found to cypermethrin, methomyl, and thiodi
carb. Resistance to the organophosphorus insecticide profenofos was fo
und in several strains. Significant resistance to B. thuringiensis Ber
liner was observed in one strain. Possible synergism of a pyrethroid i
n combination with the synergist piperonyl butoxide was observed. Imid
acloprid, representing a new class of insecticide, was found to have o
vicidal and larvacidal activity on H. virescens. Tolerance to imidaclo
prid was present in a field population resistant to carbamates but not
to organophosphorus insecticides, suggesting the possibility of cross
-resistance between carbamates and imidacloprid. Resistance to carbama
tes was clearly present in some populations susceptible to profenofos,
indicating the presence of different mechanisms of resistance for the
two classes of insecticides. Resistance to pyrethroids appears to be
stabilized at a high level.