Natural factors affecting the whitefly infestation on cassava

Abstract

The objective of this study was to determine the effects of predators, parasitoids, leaf chemical composition and levels of leaf nitrogen and potassium, total rainfall, mean temperature, sunlight and relative humidity on the attack rate of the whitefly Aleurothrixus aepim (Goeldi) on the cassava plants Manihot esculenta Crantz. It was observed a negative correlation between nymphs of whitefly and mean temperature and nymphs and adults with total rainfall. There were observed relationships between Aelothripidae with eggs, nymphs and adults of whitefly; Encarsia sp., spider Araneidae and Syrphidae with adults of whitefly; and Hyaliodes vitreus with nymphs of whitefly. Ants of the genus Crematogaster were observed associated to nymphs of this whitefly. The peaks 25.503 and 47.763min. (retention time) correlated with whitefly adults. Even though different factors, such as ecological and physiological conditions of plants, besides parasitoids and predators, can affect population fluctuation of the whitefly; the most important one for this insect seems to be the plant phenology (leaf senescense).