Effect of buckwheat farmscapes on abundance and parasitism of Pieris rapae (L.) in Virginia collards

Buckwheat, Fagopyrum esculentum Moench, with its abundant nectaries and long bloom period is often planted on vegetable farms, vineyards, and orchards to supply nectar and pollen to attract and conserve natural enemies. However, scientific data demonstrating the actual biological control benefit of such companion plantings are scarce.The objective of this experiment was to determine the effect of flowering buckwheat on the abundance and parasitism of imported cabbageworm, Pieris rapae (L), in collards, Brassica oleracea L. var. acephala DC. In 2012 and 2013, buckwheat was planted in the center of 4 spatially-isolated 150 × 8 m collard fields. Lepidopteran pest abundance and larval parasitism were compared at distances of 1,15,30,45, and 60 m from the buckwheat. Pieris rapae (L.) was the predominant lepidopteran pest species comprising over 90% of the total larvae observed on collards. No differences were detected in the abundance or parasitism of P. rapae larvae with increasing distance from buckwheat companion plantings, with parasitism averaging 68% (±1.82) across all plots and years. Although the buckwheat companion planting did not appear to have a significant effect on Pieris populations in collards, several predatory arthropod species, including anthocorids, syrphids, and cantharids were collected in high numbers from the flowering buckwheat. The population dynamics and movement of these beneficial species from the buckwheat into adjacent cash crops should be investigated in future studies.