Arthropod pest and natural enemy abundance under second-level versus first-level integrated pest management practices in apple orchards: A 4-year study

The authors conceive of second-level integrated pest management (IPM) in apple orchards as involving integration of multiple management tactics across all classes of pests. From 1991-1994, a second-level IPM pilot project was carried out in six commercial Massachusetts apple orchard blocks (2-4 ha) in which pest and natural enemy populations and injuries to fruit were compared with those in adjacent blocks receiving first-level IPM practices (considered to be integration of tactics within a single class of pests). The approach to second-level IPM was use of chemically based tactics for arthropod, disease and weed control during the first part of the growing season (up to mid-June for arthropods) and thereafter use of only biologically based tactics (cultural, behavioral and biological control methods). This article deals with findings on arthropod management. As expected, total injury to fruit by insects causing damage before mid-June did not differ between second-level (4.7%) and first-level (4.8%) IPM blocks. Total injury to fruit by insects active after mid-June averaged about the same (0.5%) in both types of blocks in 1991 and 1992, but in 1993 and 1994 it averaged more in second-level blocks (4.8%) than first-level blocks (1.9%). This was particularly true for Grapholitha prunivora Walker and leafrollers and less so for Cydia pomonella (L.) and Rhagoletis pomonella (Walsh). Among foliar pest arthropods and their natural enemies, populations of aphids and aphid predators and populations of spider mites and mite predators averaged about the same in both types of blocks. Populations of leafminers averaged lower and parasitoids of leafminers averaged greater in second-level blocks. Populations of leafhoppers averaged greater in second-level blocks. Pesticide use against fruit-damaging insects averaged 37% less in second-level than in first-level blocks, but against foliar-damaging arthropods, it was not less. Some refinements of second-level IPM tactics for arthropod control are needed before second-level IPM practices can be recommended broadly to commercial growers in New England as an economical and reliable alternative to first-level IPM.