Timing of oviposition by western flower thrips (Thysanoptera: Thripidae) in apple fruit

Adult western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), were most abundant on flower clusters of apple, Malus × domestica Borkhausen, from king bloom to full bloom. Low numbers of thrips remained on the clusters after petal fall as fruit enlarged. Thrips larvae peaked in numbers after densities of adults had peaked, usually by petal fall. Two staining procedures were developed for detecting thrips eggs in the surface of fruit ovary tissues (the edible portion of fruit), and in other blossom tissues (stamen, style, calyx, stem and leaves). Eggs were abundant in the latter tissues throughout the bloom and post-bloom periods; the calyx appeared to be highly preferred. Few eggs were detected in fruit ovary tissues during bloom. Egg numbers in ovary tissues began to increase about 8-13 d after full bloom, when fruit had grown beyond 5 mm diameter. The most effective timing of pesticides corroborated the oviposition data. Formetanate hydrochloride or spinosad caused the greatest reduction in oviposition injury (pansy spot) when applied from full bloom to about 5 mm fruit diameter.