Seasonal Occurrence of Heliothis Larvae on Cotton in Louisiana2

The bollworm, Heliothis zea (Boddie), and the tobacco budworm, Heliothis virescens (F.), are becoming increasingly important as cotton pests in Louisiana. Resistance to DDT in H. zea was first detected during 1958 (Graves et al. 1963) and now occurs in all the major cotton-producing areas of the State. However, H. virescens collected from the same fields where H. zea exhibited high levels of resistance to DDT showed no signs of having developed resistance to any of the insecticides used for cotton-insect control (Graves et al. 1964). As a result, the need arose for a thorough evaluation of the relative numbers of the 2 species on cotton throughout the growing season.