Ecological impact of three pest management systems in New Zealand apple orchards

Published source details Suckling D.M, Walker J.T.S & Wearing C.H. (1999) Ecological impact of three pest management systems in New Zealand apple orchards. Agriculture, Ecosystems & Environment, 73, 129-140.
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This study is summarised as evidence for the following.

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A replicated, controlled study in Hawke’s Bay, New Zealand in 1995-1996 (Suckling et al. 1999) found 24-58% of pest woolly apple aphid Eriosoma lanigerum colonies were parasitised by the wasp Aphelinus mali in organic orchards compared to 3-33% in conventional orchards. The wasp Dolichogenidea tasmanica parasitised 28% and 0% of leafrollers (Tortricidae) in organic and conventional apple Malus domestica orchards, respectively. The predatory mirid bug Sejanus albisignata appeared more abundant in organic than conventional orchards, but average numbers of predatory mites were similar (0.05-0.39 predatory mites per leaf overall). Woolly apple aphids were reportedly more frequent in organic (0-132 colonies/minute) than conventional orchards (0-37 colonies). In organic orchards, 59-95% of apples were undamaged compared with 90-99% from conventional orchards. Percentage fruit damage by leafrollers and woolly apple aphid in organic orchards was 1.8-4.5% and 0.002-39.6% respectively, compared with 0.1-1.2% and 0.03-11.5% in conventional orchards. Organic treatments included biological insecticide (Bacillus thuringiensis), organic fungicide, and disease control using minerals (e.g. slaked lime). Conventional orchards received 4-12 organophosphate insecticide applications and regular fungicides. Treatments were tested in 0.3-1.6 ha blocks at each of three sites.