Effect of using early-planted soybeans as a trap crop for Megacopta cribraria in commercial soybeans

Since its introduction in 2009, Megacopta cribraria (F.) has been managed in soybeans primarily by whole-field applications of broad-spectrum insecticides. We investigated the use of an early-planted soybean strip around a field perimeter as a trap crop to manage M. cribraria in the Coastal Plain of North Carolina. The rationale behind this approach is two-fold: 1) M. cribraria spatially aggregates, especially within field perimeters, and 2) higher infestations of M. cribraria have been recorded in early-planted soybeans. Twelve commercial soybean fields were selected during the growing seasons of 2014 and 2015 and planted with a ~9.5m-wide perimeter strip of early-planted soybeans (trap crop) surrounding soybeans planted at the standard agronomic time for the region in the interior; these were compared to twelve control fields (viz. fields planted at the standard agronomic time) without a trap crop. Overall, fields with a trap crop strip had higher M. cribraria populations compared to control fields. Based on localized Moran’s I statistics, M. cribraria first aggregated and established in the trap crop, with fewer M. cribraria established in the middle of these fields. In contrast, M. cribraria aggregations were found in the middle of fields with no trap crop. If a trap crop would be established, other tactics such as border sprays could accompany this proposed strategy to improve M. cribraria control and reduce the amount of insecticidal active ingredient per hectare.