Individual study: Hedgerows enhance beneficial insects on farms in California's Central Valley
Morandin L., Long R., Pease C. & Kremen C. (2011) Hedgerows enhance beneficial insects on farms in California's Central Valley. California Agriculture, 65, 197-201
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Pest regulation: Plant hedgerows
A replicated, paired, site comparison in 1999–2000 in mixed cropland in Yolo County, California, USA, found more natural enemies than pests in hedgerow shrubs, and more pests than natural enemies in weedy field edges. Ratio of natural enemies to pests: On hedgerow shrubs, natural enemies were more abundant than pests (1–3 vs 0.2–1.0 insects/m2). In weedy edges, pests were more abundant than natural enemies in summer (15 vs 8 insects/sample), but were not significantly different in spring (6 vs 4) or fall (9 vs 4). A higher proportion of insects were natural enemies in hedgerow shrubs than in weedy edges (0.81–0.88 vs 0.32–0.46). Methods: On the edges of four crop fields, native shrubs (hedgerow shrubs), bordered by native grasses (hedgerow grasses), were planted in 1996 (305–550 m), and compared to the weedy edges of the same fields every two weeks in March–November 1999–2000. Insects were observed on hedgerow shrubs (four minutes/shrub species), collected from shrubs by shaking, and collected from hedgerow grasses and weedy edges with sweep nets (10 sweeps/sample; four samples each).