Oviposition Habits of Trichogramma minutum on Artificial Concentrations of Eggs of the European Pine Shoot Moth

Abstract

Pupae of the European pine shoot moth, Rhyacionia buoliana (Schiffenmiiller), were placed in 18/inch-mesh screen cages attached to red pine branches. The eggs produced by the resulting moths were examined for relationships between egg-mass size and location on needles, to parasitism by Trichogramma minutum Riley and occurrence of nondevelopment. From 1 to 18 eggs were laid at each site; eggs were laid singly at 40% of the sites, and at 93% of the sites 5 eggs or fewer were laid. The rate of parasitism was 30% in egg masses with 4 eggs each, and was progressively lower in masses with more or fewer eggs. T. minutum oviposited in every egg in masses of 2-5 eggs 20% more frequently than would be expected if oviposition were random. Most eggs (87%) were deposited on the concave surface of needles. Nondevelopment of eggs was most common in eggs laid singly and in those laid on the convex surface of the pine needles.