Everett C. Burts

Effect of native natural enemies and augmentative releases of Chrysoperla rufilabris Burmeister and Aphidoletes aphidimyza (Rondani) on the population dynamics of the green apple aphid, Aphis poMi De Geer

Abstract The impact of native natural enemies, supplemented by augmentative releases of the green lacewing, Chrysoperia rufilabris Burmeister (Neuroptera: Chrysopidae), and/or the cecidomyiid, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae), on the population dynamics of the green apple aphid, Aphis pomi De Geer (Homoptera: Aphididae), was assessed in a series of experiments conducted in north central Washington State, USA. In one trial, C. rufiabris alone was released at a rate of 200 eggs or first instar larvae per tree per week for 6 weeks; in a second experiment, it was released in combination with A. aphidimyza at rates of 400 eggs and 250 pupae respectively per tree per week. In a final trial, A. aphidimyza alone was released at a rate of 200 pupae per tree per week for the duration of the growing season. The dominant native natural enemies in the study area were Chrysopa nigricornis Burmeister, A. aphidimyza. Onus sp. (Hemiptera: Anthocoridae), and various species of Syrphidae, Chamaemyii...

Seasonal susceptibility to insecticides in insecticide-resistant pear psylla, Psylla pyricola (Homoptera: Psyllidae)

Seasonal changes in susceptibility of adult winter and summer forms of insecticide-resistant pear psylla, Psylla pyricola Foerster, to several insecticides were evaluated using slide-dip and topical application bioassays. Insecticides tested were azinphos-methyl, endosulfan, fenvalerate, methiocarb, Perthane, amitraz and avermectin. Throughout the period of testing, LD50 values generally were lowest for avermectin followed by fenvalerate < methiocarb < endosulfan < azinphos-methyl < Perthane. The topical application method showed that winter forms of pear psylla were more tolerant to azinphos-methyl, methiocarb, endosulfan, Perthane and fenvalerate than summer forms. Susceptibility to most insecticides increased for both forms as the season progressed. The slide-dip test showed similar trends to the topical application method for azinphos-methyl, methiocarb and endosulfan. However, slide-dip tests for formulated fenvalerate showed lower susceptibility in summer forms than in winter forms. This was consistent with field control results obtained with this compound. With both bioassays, seasonal tests with amitraz showed little effect on adults. Applications of results to control and resistance management of pear psylla are discussed.