HISTOLOGICAL STUDIES ON THE STYLET PATHWAY, FEEDING SITES AND NATURE OF FEEDING DAMAGE BY PLANOCOCCUS CITRI (RISSO) (HOMOPTERA: PSEUDOCOCCIDAE) IN SWEET ORANGE

Abstract

HISTOLOGICAL STUDIES ON THE STYLET PATHWAY, FEEDING SITES AND NATURE OF FEEDING DAMAGE BY

PLANOCOCCUS CITRI (RISSO) (HOMOPTERA: PSEUDOCOCCIDAE) IN SWEET ORANGE.

Histological studies on the stylet pathway, feeding sites and cell damage caused by the citrus mealybug, Planococcus citri (Risso), on sweet orange (Citrus sinensis (L.) Osbeck) fruit and leaves are described. The frequency of stylet pathways that were exclusively intercellular did not differ significantly from those that were both inter- and intracellular. Stylet track terminations were significantly more frequent in the phloem and its proximity than elsewhere, indicating that the phloem was the preferred feeding site in both fruits and leaves. None of the observed stylet tracks had multiple branches. The majority of plant cells surrounding the stylet tracks showed no detectable damage; only in the fruit did some cells appear slightly enlarged and had a different pigmentation, suggesting that the damage was caused by diffusion of saliva from the stylet. The pierced cells appeared otherwise healthy.

Key words: feeding behaviour