EFFECT OF ENDOTOXIC COMPOUNDS ISOLATED FROM VERTICILLIUM-LECANII ON THE SWEET-POTATO WHITEFLY, BEMISIA-TABACI

Toxic products extracted by methanol from intact mycelia of Verticilli um lecanii were tested for their toxicity to eggs. larvae, pupae and a dults of Bemisia tabaci and additional insects. All stages of B. tabac i were sensitive to the toxin, with larvae showing the highest, and ad ults the lowest, sensitivity. Using a 0.5% crude toxin preparation, th e mortality rate of B. tabaci was 88%, 53.5%, 53.2% and 37% for larvae , eggs, pupae and adults, respectively. High sensitivity of adults, wh ich was characterized by rapid paralysis followed by death, was observ ed in B. tabaci, Myzus persicae, Aphis gossypii, Acyrthosiphon pisum a nd Frankliniella occidentalis. Other insects, viz., Heliothis peltiger a, Maladera matrida, Carpophilus hemipterus and Ceratitis capitata, ex hibited significantly lower sensitivity. The toxin was partially purif ied by differential extraction with organic solvents and on silica gel H and Sephadex LH 20 columns. Based on the toxin inactivation by sapo nification and its mobility in a polar solvent on thin layer chromatog raphy, it is suggested that the toxic products might be phospholipids.