Trap cropping harlequin bug: Distance of separation influences female movement and oviposition

Authors: Bier, Alexander; WALLINGFORD, ANNA - University Of New Hampshire; Haber, Ariela; Herlihy-Adams, Megan; Weber, Donald

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2021
Publication Date: 3/11/2021
Citation: Bier, A.D., Wallingford, A.K., Haber, A.I., Herlihy, M.V., Weber, D.C. 2021. Trap cropping harlequin bug: Distance of separation influences female movement and oviposition. Journal of Economic Entomology. https://doi.org/10.1093/jee/toab022.
DOI: https://doi.org/10.1093/jee/toab022

Interpretive Summary: The harlequin bug is a serious stink bug pest of brassica crops, and new tools are needed for vegetable growers to manage this pest with reduced or no pesticide inputs. One tactic is trap cropping, which aims to divert pest insects away from cash crops by attracting them to an alternative trap crop nearby. Mustard greens are more attractive to harlequin bug than are collards and related cole crops, and thus are a candidate trap crop. However, bugs may not remain on this trap crop, depending on how many accumulate there, and how much separation there is from the cash crop to be protected. In this study, we evaluated, using greenhouse experiments and separate spring and fall collard plantings, the influence of the presence of a mustard trap crop, planted planted around the collards either as an adjacent border trap crop, or as a separated surrounding border trap crop, or with no trap crop. We confirmed that harlequin bugs prefer mustard and that immigrating adults accumulate there. Females, however, move to collards to lay their eggs, "commuting" between the trap crop and the collard cash crop; we confirmed this behavior in the greenhouse and field experiments. In the field, a separation of only two rows (7.5 feet = 2.3 meters) reduced eggs laid on the collards, and feeding damage, by over 75%. This shows that the spatial arrangement of the mustard trap crop, and its separation from the cash crop, can impede bug movement including female commuting and egg-laying, thus better protecting the collard cash crop. The results of this research will be useful in developing trap cropping plans to manage this serious pest, and will be of interest to pest managers and researchers developing environmentally-friendly methods to manage vegetable pests.

Technical Abstract: To evaluate a border trap crop approach for the management of harlequin bug, Murgantia histrionica (Hahn), we undertook greenhouse and field experiments with mustard greens as trap crop for a collard cash crop. We confirmed that harlequin bugs prefer to reside on mustard and that immigrating adults accumulate there. Females, however, in greenhouse cage experiments, moved to collards to lay their eggs, "commuting" between the trap crop and the collard cash crop. Separate spring and fall field plantings, using replicated 12m by 12m collard plots in a 1-hectare field, tested the influence of the presence of a mustard border trap crop planted around the collards either as an adjacent border trap crop, or as a separated surrounding border trap crop, or with no trap crop. In the spring field planting adults accumulated on the mustard crop but overall numbers remained low, with all collards sustaining <1% leaves with damage. In the fall crop, a separation of only two rows (2.3 meters) reduced eggs laid on the collards by four-fold, and feeding damage, from over 20% to ~5%. Fall planting control plots with no border trap crop showed even lower foliar damage, under 2.5%. Likely this is a result of initial colonization of immigrating harlequin bugs overwhelmingly to mustard at the field (hectare) scale, resulting in fewer bugs near the control treatments at the plot (<0.05 ha) scale. Thus, the spatial arrangement of the mustard trap crop, and its separation from the cash crop, influences bug colonizations, and can reduce bug movement including female commuting and egg-laying, thus better protecting the collard cash crop.