[Influence of the webbing produced by Oligonychus ilicis (McGregor) (Acari: Tetranychidae) on associated predatory phytoseiids].

Oligonychus ilicis (McGregor) is among those mite species that can cause damage to coffee plants (Coffea spp.). Species of Phytoseiidae acari are considered the most important and studied predatory mites. The objective of this study was to evaluate the effects of the webbing produced by O.ilicis on its predation by females of the phytoseiids Iphiseiodes zuluagai Denmark & Muma, Euseius citrifolius Denmark & Muma and Amblyseius herbicolus (Chant). Four bioassays were conducted, with three treatments and ten replicates. Each replicate consisted of 25 O.ilicis per experimental unit (a leaf disc of Coffea arabica) according to the tested developmental stage, in independent experiments. To spin the web, 15 adult females were put on each experimental unit for 24h; females were then removed, leaving only the web, and predators and prey to be tested were introduced. Predation was assessed after 24h. In the presence of webbing, the consumption of eggs, larvae and nymphs by I.zuluagai and eggs and larvae by E.citrifolius was lower. For A.herbicolus, egg predation was lower, but larval predation did not vary significantly and predation of nymphs and adults was higher in the presence of webbing. Predators as a whole were more efficient consuming larvae regardless of the presence of webbing. Considering the stages of O.ilicis altogether, webbing reduced the predation potential of I.zuluagai and E. citrifolius, but not of A. herbicolus.