BIOLOGICAL PEST CONTROL WITH CONTINUOUS GREENHOUSE CULTURE

Abstract

A strategy for controlling pests with biological control was sought for production of salad greens and herbs in a nutrient film technique (NFT) growing system. A case study was initiated in October 1989 using a one half hectare greenhouse range (1988 construction) with no past or present synthetic insecticide use. Problematic pests were aphids and thrips. A natural predator/pest cycle (NPC) area was established (5% of total greenhouse area with potted herbs on benches) to provide an area for predators to establish and reproduce. Introduced predators, which successfully reproduced in the greenhouse, were Apidoletes aphidimyza (aphid control), Amblyseius macKenzie, and A. cucumeris (thrip control), Encarsia formosa (whitefly control), and Phyoseiulus persimilus (two spotted spider mite control), Naturally occuring predators of importance included a wasp parasitoid of aphids (Hymenoptera) and an insect predator, the minute pirate bug (Hemipters, Anthocoridae), which feeds on thrips and aphids.Two flying predators of aphids (A. aphidimyza and the wasp parasitoid) dispersed well from the NPC area and provided effective control. The technique of applying the thrips predators, a slow moving mite to flats shortly before transplanting provided good dispersal on all transplants. The time for effective control by the predator was 4 to 6 weeks. Effective control was observed in chives but not shorter cycle crops (3 to 5 weeks average). Immature minute pirate bugs were also observed in the chives assisting in control. Effective spider mite control was accomplished 2 to 3 weeks after the release of P. persimills into infested area. Whitefly populations have been effectively controlled by E. formosa.