A survey of the Arthropod fauna of plum trees at East Malling in 1966

Abstract

In an investigation of the fauna of plum at East Mailing Research Station in 1966, over 70 species of the commoner arthropods were listed.Different species of mite were found to prefer different parts of the tree, different parts of the leaf, and leaves of different ages on a shoot. Aculus fockeui (Nal. & Trt.) (Eriophyidae) was found to spread up the shoots during the early summer and to attain a density of over 100 per sq. cm. of leaf surface. Panonychus ulmi (Koch) was found to be commoner to the east of the tree, and leaf damage that it caused graded in severity across the plot. The species composition of populations of the Phytoseiid mites could differ markedly between trees in the same plot.A study of the population trends of the commoner species based on numbers per shoot revealed that the populations of aphids and their predators developed two peaks during the season. There was a relatively high incidence of Entomophthora infection on the aphids, and overwintering fungal spores were produced when the aphids died in crevices on the bark, but only short-lived cornidia when they died on the leaves. The population density of member species of the fauna varied considerably, the smallest phytophagous mites reaching levels of 200 per shoot, predacious mites 10.0 per shoot and predatory bugs such as Blepharidopterus angulatus (Fall.) only about 0.01 per shoot.