REPELLENCE, MORTALITY AND OVIPOSITION OF Trialeurodes vaporariorum (West.) WITH ALKALOIDS OF Erythrina americana Mill.

Abstract

Trialeurodes vaporariorum (West.), or greenhouse whitefly, is a phytophagous insect that causes economically important damage to plants. It is controlled, alternatively, with plant extracts such as those of Erythrina americana Mill., whose seeds contain alkaloids. The objective of this study was to evaluate the activity of the methanol extract, fractions and alkaloids of this material applied on bean leaflets on repellence, mortality and oviposition of T. vaporariorum adults. Repellence was quantified on 20-day-old bean leaflets submerged in the treatments as the number of insects on the leaflets after 3, 24, 48 and 72 h. Mortality and inhibition of oviposition was determined at 24 h by the number of dead insects and the number of eggs on 20-dayold bean plants sprayed with the treatments. The results were analyzed with ANOVA and the Tukey test, or the KurskalWallis test and the Mann-Whitney U, and Probit was carried out. The methanol extract at a concentration of 0.22 to 1.28 mg mL-1 caused 50% repellence and mortality but did not impede oviposition. The liberated alkaloids at concentrations of 0.05 to 1.75 mg mL-1 produced 50% repellence and mortality, but a higher concentration is required to inhibit oviposition. Liberated alkaloids at concentrations of 0.72 to 1.06 mg mL-1 caused 50% repellence, mortality and inhibition of oviposition. The alkaloids b-erythroidine and erysodine, in terms of repellence and mortality, showed the same activity as the free and liberated alkaloids. b-erythroidine stimulated oviposition and erysodine inhibited it by 70%. The methanol extract and fractions, as well as the alkaloids b-erythroidine and erysodine produced repellence, mortality and inhibited oviposition on bean plants. Therefore, they can be used for crop protection.