MORTALITY OF FALL ARMYWORM, SPODOPTERA FRUGIPERDA (LEPIDOPTERA: NOCTUIDAE) EGGS, LARVAE AND ADULTS EXPOSED TO SEVERAL INSECTICIDES ON COTTON
Mortality of eggs, first, third, and fifth instars and adults of fall army worm (FAW), Spodoptera frugiperda (J. E. Smith), after exposure to several insecticides on cotton indicated that the FAW is susceptible to most insecticides currently used to control Heliothis spp. Most insecticides tested exhibited ovicidal activity. High mortality of first instar larvae was observed for most treatments, including the biological insecticide, Bacillus thuringiensis (Berliner). More variation in mortality among treatments was observed in third and fifth instars than in first instars. Pyrethroid, carbamate, and organophosphorous insecticides resulted in higher mortality than did B. thuringiensis. Diflubenzuron, an insect growth regulator, was as effective as commonly used insecticides against third and fifth instar larvae when mortality was observed at pupation. Third instar FAW placed on plant tissue from the upper section of cotton plants sprayed in field situations suffered higher mortality than those placed on plant tissue from lower sections in the plant canopy. Inadequate deposition of insecticide in the lower portions of the cotton plant appears to be a limiting factor in control of FAW larvae on cotton.