Effectiveness of some pesticides against Cacopsylla pyri and impact on its predator Anthocoris nemoralis in pear-orchards

During 2001-2002, in the scope of an IPM programme, a research was carried out on the impact of treatment with broad spectrum and selective insecticides on the population dynamics of the pear psyllid Cacopsylla pyri (L.) (Homoptera Psyllidae) and its predator Anthocoris nemoralis (F.) (Heteroptera Anthocoridae) in a pear orchard of the variety “Krystalli”, near Koropi in Attica, Greece. At the same time the beneficial insect fauna on the wild vegetation edging the orchard was recorded and its role as natural ecological resource and dynamic source of beneficial insect populations was estimated. A programme of treatments with the broad spectrum insecticides (deltamethrin, amitraz) effectively controlled C. pyri. However, these were also highly toxic to A. nemoralis, the most predator in the area under survey, whose active period and population dynamics coincide with those of the psyllid. In contrast, a program of treatments with insect growth regulators (diflubenzuron, fenoxycarb) and potassium salts was equally effective against C. pyri but showing less toxic activity on A. nemoralis that at times was found in higher densities than the psyllid. On the four plant species of which the wild vegetation at the edge of the orchard was composed, 12 predator species, belonging to three families, were recorded. Out of these, A. nemoralis with a relative frequency of 61% in average prevails by far over the other species. It occurs mainly (73% in average of all records) on Cercis siliquastrum L.