Individual study: Manipulating floral resources dispersion for hoverflies (Diptera: Syrphidae) in a California lettuce agro-ecosystem
Gillespie M., Wratten S., Sedcole R. & Colfer R. (2011) Manipulating floral resources dispersion for hoverflies (Diptera: Syrphidae) in a California lettuce agro-ecosystem. Biological Control, 59, 215-220
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Pest regulation: Plant flowers
A replicated before-and-after study in 2007 in lettuce fields in the Salinas Valley, California, USA, found more pests, more predators, and different distributions of predators after restoring floral resources compared to before. Pest and natural enemy numbers: After restoring sweet alyssum Lobularia maritima rows, there were more pests (12.5 vs 8.5 currant-lettuce aphids Nasonovia ribisnigri per lettuce) and more hoverfly eggs and larvae (2.3 vs 1.2 eggs/lettuce; 1.4 vs 0.8 larvae/lettuce) than there were before (second sampling dates). After restoration, there were more hoverfly adults near restored flower strips (72 vs 57), but fewer elsewhere in the field (60–76 vs 77–95), than there were before. Methods: Flower strips were planted 48 m apart on four lettuce fields. Access to one flower strip/field was restricted (strips were covered on 31 August) and then restored (covers were removed on 5 September). Insects were sampled (2–5 days after restriction and restoration) by searching lettuce heads or by counting hoverflies on transects.