Aphytis melinus DeBach (Hymenoptera: Aphelinidae) is an important parasitoid used in augmentative biological control of California red scale, Aonidiella aurantii (Maskell), a key citrus pest. In California citrus systems, insecticides are applied during spring and early summer to manage citrus thrips, Scirtothrips citri (Moulton), a period that overlaps with peak A. melinus activity. To support integrated pest management strategies for red scale, we evaluated the residual effects of citrus thrips insecticides on A. melinus adults. Foliar applications of insecticides were made to ‘Washington’ navel orange trees at the Lindcove Research and Extension Center, Exeter, CA, in May. For the bioassay 10-inch twigs/tree were randomly collected from the outer canopy, from five replicate trees per treatment. Twig samples were transported in labeled paper bags on ice-chest to the Kearney Agricultural Research and Extension Center, Parlier, CA where bioassays were conducted. Each twig was place placed in 1-gallon glass jars, and 50 adult A. melinus reared on Aspidiotus nerii (Oleander scale) were released. Jars were sealed with paper towels and held at 77°F under ambient light. Mortality was recorded after 24 h. Results show that all insecticides except Spear T affected survivorship in week 1. In week 2, Spear T, Alluma + AzaPro + and Cinnerate, and PQZ had ~90% survival and were similar to control. The treatments that had the longest residual activity were Plinazolin SC 400 and Bexar.
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