Distribution of Citrus Bud Mite (Acari: Eriophyidae) within Lemon Trees

Abstract

The percentage of lemon axillary buds infested by citrus bud mite, Aceria Sheldoni (Ewing), varied with the age of twigs. Infestation declined sharply between buds on twigs that were mostly green and just beginning to develop bark (twig age 3) and buds on twigs where bark formation was more advanced and less than half of the surface was still green (twig age 4). The relative infestation of buds on young twigs (ages 0-3) varied between two groves that were studied, but, generally, green twigs that were angular in cross section rather than round (twig age 1) were as heavily infested or more so than any other twig age. New, elongating twigs (twig age 0) were infested almost as soon as they developed regardless of the time of year. Feeding damage increased as twigs aged, and accumulated feeding damage may have been largely responsible for the relatively low levels of infestation of buds from older twigs. The southern halves of the trees were significantly more infested than the northern halves. Within quadrants, the variation in infestation among buds on different twigs usually was greater than variation among buds on the same twig, suggesting a clumped distribution. The percentage of infested axillary buds was correlated with the percentage of fruit that was infested with bud mites under the calyx.