Impact of predatory carabids on below- and aboveground pests and yield in strawberry

Authors: Lee, Jana; Edwards, David

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2011
Publication Date: 11/24/2011
Citation: Lee, J.C., Edwards, D.L. 2011. Impact of predatory carabids on below- and aboveground pests and yield in strawberry. Biocontrol. 54:515-522.

Interpretive Summary: Carabid beetles are important generalist predators found in many agricultural fields; they consume weed seeds, slugs, and insect pests. Most of the studies on carabids have focussed on pests aboveground. However, carabids spend part of the day belowground and could impact belowground pests. The impact of adult carabid beetles on pests and fruit yield was examined for two years in a strawberry field. We manipulated the density of adult carabids in 2 m x 2 m plots enclosed with barriers, and compared these plots to open control plots. Adult carabids did not appear to substantially remove sentinel black vine weevil larvae and pupae that were buried belowground. The presence of carabids resulted in higher removal rates of red clover seeds placed on the surface and the number of marketable strawberry fruits in June. In the laboratory, several carabid species consumed weevil eggs, larvae or pupae placed on the surface. However, the consumption of weevil larvae by adult carabids decreased when larvae were buried or allowed to burrow naturally into the roots of potted strawberry plants.

Technical Abstract: The impact of adult carabid beetles on below- and above-ground pests and fruit yield was examined in a two-year strawberry field study. Plots (2 m x 2 m) enclosed with barriers were used to augment or exclude adult carabids, and compared to open control plots. Pterostichus melanarius was the predominant carabid captured in pitfall traps, especially during the summer and fall period. Manipulating the density of adult carabids had no impact on the removal of sentinel black vine weevil, Otiorynchus sulcatus, larvae and pupae that were buried belowground, but had a significant impact on the removal of red clover, Trifolium repens seeds placed on the surface and the number of marketable strawberry fruits in June. Plots where carabids were excluded resulted in lower weed seed removal and fewer marketable fruits compared to augmented or control plots. In the laboratory, several carabid species consumed O. sulcatus eggs, larvae or pupae placed on the surface, but consumption of O. sulcatus larvae was less frequent as the complexity of the arena increased. More P. melanarius consumed prey larvae placed on the soil surface than larvae buried 1.3 or 5 cm below, and most carabid species showed no impact on O. sulcatus larvae that had burrowed into the root of potted strawberry plants.