ABSTRACT

LD50s of cypermethrin were determined for 14 single pairs of PY-R strain of the tobacco budworm, Heliothis virescens (F). LD50s of profenofos were determined for 25 single pairs of PY-R strain of the tobacco budworm, H. virescens (F). The range of LD50s was 937 and 195, respectively. Differences indicate polygenic factors for resistance. All significant and non-significant regressions of single pairs were resistant to cypermethrin and 36% were resistant to profenofos. Multiple resistance was evident in 18% of the single pairs.