Is Everything Connected? Following the Predators, Pests, and Plants Within a No-Till, Western Montana Agroecosystem

摘要: Smith, Ethan A., M.S., Autumn 2006 Environmental Studies An Evaluation of Interactions between the Imported Cabbage Worm (Pieris rapae), an Assemblage Six Arthropod Predators, and Two Insecticides Within a Minimum-Till Brussels Sprouts Agroecosystem Chairperson: Neva Hassanein Agricultural systems are being re-engineered with hedgerows, living mulches, or minimum tillage activities in hopes retaining populations beneficial, predatory insects that may decrease need for pesticide use. The purpose this research was twofold. First, on-farm assessed population activity six beneficial arthropod predators carabid beetle (Carabidae: Coleoptera), minute pirate bug (Orius spp.: Hemiptera), nabid (Nabis lady larvae (family Coccinellidae: syrphid fly (Syrphidae: Diptera) spiders (Araneae) one crop pest imported cabbage worm rapae: Lepidoptera) within no-till sprouts (Brassica oleracea, gemmifera group) red clover (Trifolium pratense) living-mulch system. Second, using two common organic insecticides Bacillus thuringiensis var. kurstaki (Bt) pyrethrin/rotenone blend – capacity these aforementioned parasitic arthropods to control P. rapae damage through biological (as compared chemical) means. Field investigations predators/pests involved weekly sweep-net sampling, pitfall trap installation, direct plant examination. were applied as bi-weekly “calendar” application (pyrethrin/rotenone) pest-density “threshold” dependant (Bt). Generally, prevention more successful Bt treatments than treatments. pesticides had no significant effect on any sampled, while insecticide appeared significantly reduce levels all sampled. lowest treated plots, moderate plots (no applied, yet natural present) , highest sprays. Preliminary results indicate worked additive measure, which then augmented predator populations. increased coincided reduced “beneficial” insect numbers other disruption multiple-arthropod assemblage kept impacts lower “control” plots.