Evaluating trapping methods to increase earwig capture in temperate tree fruit crops

The European earwig, Forficula auricularia L. (sensu lato), has a dual role in temperate tree fruit crops-a pest of stone fruit and a predator of key pests in pome fruit. Some growers trap earwigs in crops where they are pests, subsequently releasing them in pome fruit as an augmentative biological control strategy. Effective earwig monitoring and trapping are critical for understanding their biological control potential in orchards. Traps made of rolled, corrugated cardboard have long been used for earwig monitoring; however, no standardized studies have investigated improvements to them. In a series of trials, we explore options to improve traps by testing different trap materials, sizes, positioning on the tree, and time in the field, in addition to the lures and baits. We found that cardboard traps had higher earwig catch than black or translucent plastic traps. There were diminishing returns in earwig capture for increased trap length, plateauing at ~30 cm. Traps placed on the main trunk captured more earwigs than traps on the base or near the end of branches. Lures and baits mostly did not increase trap efficacy, except fish sauce which inconsistently increased earwig captures. The use of plastic bottles to contain the cardboard traps greatly reduced trap catch. Finally, we found evidence that traps left in the field for longer periods of time can increase earwig capture, possibly due to the accumulation of earwig aggregation pheromone. Overall, the standard unbaited corrugated cardboard trap was the most effective and practical earwig monitoring trap.