Effect of endotoxic compounds isolated from Verticillium lecanii on the sweetpotato whitefly, Bemisia tabaci

Toxic products extracted by methanol from intact mycelia of Verticillium lecanii were tested for their toxicity to eggs, larvae, pupae and adults of Bemisia tabaci and additional insects. All stages of B. tabaci were sensitive to the toxin, with larvae showing the highest, and adults the lowest, sensitivity. Using a 0.5% crude toxin preparation, the mortality rate of B. tabaci was 88%, 53.5%, 53.2% and 37% for larvae, eggs, pupae and adults, respectively. High sensitivity of adults, which was characterized by rapid paralysis followed by death, was observed in B. tabaci, Myzus persicae, Aphis gossypii, Acyrthosiphon pisum and Frankliniella occidentalis. Other insects, viz., Heliothis peltigera, Maladera matrida, Carpophilus hemipterus and Ceratitis capitata, exhibited significantly lower sensitivity. The toxin was partially purified by differential extraction with organic solvents and on silica gel H and Sephadex LH 20 columns. Based on the toxin inactivation by saponification and its mobility in a polar solvent on thin layer chromatography, it is suggested that the toxic products might be phospholipids.