Relative densities of natural enemy and pest insects within California hedgerows

Published source details Pisani Gareau T.L., Letourneau D.K. & Shennan C. (2013) Relative densities of natural enemy and pest insects within California hedgerows. Environmental Entomology, 42, 688-702.
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This study is summarised as evidence for the following.

	Action	Category
	Pest regulation: Plant hedgerows Action Link

Pest regulation: Plant hedgerows

A replicated site comparison in 2005–2006 on organic vegetable farms on the Central Coast, California, USA, found similar ratios of natural enemies to pests in hedgerows compared to weedy edges, and in fields with hedgerows compared to fields with weedy edges. Ratio of natural enemies to pests: The ratio of natural enemies to pests (2005: 11:1 enemies:pests; 2006: 15:1) was not significantly different between fields with hedgerows and fields with weedy edges, either at the edge (30:1 vs 6:1 enemies:pests), or 50–100 m into the field (3:1 enemies:pests). Different plant species in hedgerows had different ratios (from 4:1 enemies:pests on toyon Heteromeles arbutifolia in 2005 to 43:1 on coyote bush Baccharis pilularis in 2006). Methods: Two fields with hedgerows (>2 years old) and two fields with weedy edges were compared. Insects were sampled using yellow sticky cards (2005: five cards each at 0, 50, and 100 m into fields, collected after three days) and vacuums (2005: 30 seconds/plant in hedgerows; 2006: 60 seconds/plant).