CONTROL OF EDAPHIC POPULATIONS OF WOOLLY APPLE APHID USING ENTOMOPATHOGENIC NEMATODES AND A SYSTEMIC APHICIDE

The effects of an entomopathogenic nematode, Steinernema carpocapsae (Weiser), and an experimental systemic aphicide, RH-7988, on edaphic populations of the woolly apple aphid, Eriosoma lanigerum (Hausmann), were investigated. Laboratory experiments showed that presence of the nematode in a culture of woolly apple aphids increased the mortality rate. Nematodes were found inside the body cavity of several aphids with entry possibly being through the anus via a droplet of honeydew. Field trials in an unsprayed six-year-old and four-year-old apple orchard tested the efficacy of broadcast spray and topdressing applications, respectively, of nematodes at a rate of 376,600 nematodeS/m2. The broadcast spray trees had fewer aphid colonies on roots than the untreated controls (P = 0.10), but the topdressing treatment had no effect. The systemic aphicide, RH-7988, was tested in a two-year-old apple orchard. Two rates of foliar and soil application were tested, with all treatments significantly reducing arboreal woolly apple aphid populations. Edaphic populations were also significantly reduced one month after treatment, but no difference was found four months after treatment. Both control methods show promise as potential management options for edaphic woolly apple aphid populations.