BIOLOGICAL CONTROL Seasonal and Diurnal Dynamics of Beneficial Insect Populations in Apple Orchards Under Different Management Intensity

Limb jarring sampleswere taken in fourexperimental appleorchards (onecompletely unmanaged; one with horticultural management and no pest management; one with horticultural management, no pest management, and interplanted with peach and sour cherry; and one under conventional commercial management practices) at hourly intervals over a 24-h period at four times in 1991. A total of 1,176 individual predators belonging to seven orders and 22 families was collected. The most abundant species was Coniopteryx sp. (Coniopteryigidae: Neuroptera), and the most abundant family was Coccinellidae (Coleoptera). A total of 396 adult parasitoids was collected from 26 families of Hymenoptera and one Diptera family, with Encyrtidae being the most abundant. All other individuals were classiÞed as potential food items and were identiÞed only to order or, in some instances, family. A total of 5,812 potential food items was collected. Diversity of predators and parasitoids was greatest in May and June. Diversity of predators was highest on apple trees that were inter-planted with peach and cherry trees, whereas parasitoid diversity was greatest on peach trees and on insecticide treated apple trees. Chrysopids (Neuroptera), clerids (Coleoptera), and Leptothrips mali (Fitch) (Phlaeothripidae: Thysanoptera) were most commonly collected at dawn or during the night, suggesting that their role in orchards may be underestimated by sampling only during daylight hours. With the exception of Scelionidae and Platygastridae (Hymenoptera), parasitoids were most commonly collected during the night. Results indicate that peach trees are attractive to both predators and parasitoids and therefore may be a valuable addition to apple orchards to enhance the abundance of biological control species.