Red Scale Parasite (Aphytis melinus) California red scale is the favorite prey of these parasitic wasps, although citrus red scale, oleander scale, San Jose scale, ivy scale, and citrus yellow scale are other prey. Aphytis are shipped as adults, and the adult females lay their eggs in red scale. The larvae consume their host, and each A. melinus kills more than 30 scale insects.
Description: Aphytis melinus is a small light yellow parasitic wasp about 1mm in size. The wasp parasitizes various types of armored scale. The wasp lays eggs under the waxy scale covering, created by the scale. The parasite larvae develop under the scale covering. The window for female control is during the second and third instars of development while she is a virgin. The male's window is during the second instar and pre-pupae development. It is during these developmental stages that the scale is not affixed to host plant thus allowing the parasites to get under the scale. In some cases the scale is killed by adult hosts feeding on them. Once the scale is parasitized it looks dried out and when examined closely may have dark spots. Life Cycle: At 80° F Aphytis take 13-18 days to develop from egg to adult. Adults live for approximately 10-16 days (up to 25) and deposit 6-8 eggs daily.
Use in Biological Control
Aphytis melinus are available in plastic cups of 5,000-30,000. In general they should be released regularly (1-3 week intervals) at the first sign of scale in the spring until low scale populations are maintained.
To build an established population in orchards, 1-2 cups/acre should be released every other week until the scale population is reduced to a low level. Release on the shaded side of the trees at temperatures below 90° F. Release some parasites every sixth tree every sixth row starting at a different row each week to assure even distribution. The parasites can be released either by leaving an opened cup in a tree infested with scales or by walking though the orchard with an opened cup for more rapid dispersal. Afterwards an annual release of ½ -1 cup/acre is recommended in the spring. Use a summer oil spray to reduce high number of scales 2-3 weeks before releasing parasites.
For interior plantings, regular releases of A. melinus work best and can control infestations in 2-3 months. Afterwards 1-3 releases/year should be sufficient to maintain control. The release rate depends on the suitability of the scale host. A guideline rate is 5-10 parasitoids/ infested plant or 10/sq. yard. Release parasites by waving an opened cup around infested plants 2-3 times at 2-3 week intervals. Release at dusk or with the windows shaded so the Aphytis will find infested plants quicker. If initial scale populations are high, apply insecticidal soap 2-3 weeks before 1st release. Wash off honeydew accumulations off plants just before release.
Use parasites same day of arrival. If necessary to hold, keep cool (approx. 60° F) and dark until use. Do not refrigerate or place insects directly next to cold packs. Viability decreases rapidly with prolonged storage.