Assessing effective mechanical and chemical strategies for managing Eucosma giganteana (Lepidoptera: Tortricidae) in the perennial oilseed crop, Silphium integrifolium (Asteraceae: Heliantheae).

Abstract

Eucosma giganteana (Riley) is a native specialist pest of silflower, Silphium integrifolium Michx., which is currently being domesticated as a perennial oilseeds crop. The larvae of this moth attack silflower capitula and root crowns, causing both seed damage and long-term degradation of plants. To determine methods to manage E. giganteana in silflower crop fields, we conducted a laboratory bioassay and 3 field experiments to assess the effects of a suite of organic, conventional, and mechanical treatments on E. giganteana mortality and colonization of flower heads. Pyrethroids (permethrin, cyfluthrin), chlorantraniliprole, and methoxyfenozide each had significant insecticidal effects on E. giganteana in at least 2 of the experiments conducted. Nematodes marginally increased larva mortality in the laboratory bioassay and could be further investigated as a soil-applied biological control. In 2 separate field experiments, trimming the top 15% of silflower plants to delay flowering did not alone reduce E. giganteana colonization of flower heads throughout the growing season. However, when trimming was paired with a single chlorantraniliprole application, colonization of capitula was reduced by 83% over untreated control plants. Collectively, these experiments provide evidence for several treatments that could be further tested and incorporated into an integrated pest management strategy for E. giganteana.