Contrasting late season pest insect abundance in non‐crop vegetation areas and nearby canola fields in the Canadian Prairies

Abstract

Non‐crop vegetation areas in agricultural landscapes are vital for maintaining biodiversity. However, they potentially host pest insects, which can cause economic loss in crop fields. Some insect species have been found to spill into crops from these areas, but this varies depending on species, landscape composition and the time of the season. To determine if five common pest insects of canola crops were spilling into fields during the late growing season, we collected samples at various distances from non‐crop areas, in a part of the Canadian Prairies (Alberta, Canada) where this crop is widely grown. Sampling occurred at 15 sites in each of 10 fields (N = 150 sites). We modelled changes in pest abundance over distance from the non‐crop areas and contrasted the abundance of each taxon in the crop and non‐crop areas. Only leafhoppers (Hemiptera: Cicadellidae) demonstrated a declining gradient in abundance that is consistent with spillover from non‐crop vegetation areas into the canola fields. Weevils were found to have significantly higher abundance in the non‐crop areas, indicating a relationship between this taxon and the non‐crop area in the late season, but there was no decline in abundance, which might indicate spillover occurring. All taxa demonstrated spatial differences in abundance among fields. This study found limited evidence that the pests are spilling over from non‐crop vegetation into canola crops during the late season. Therefore, movement of pests from non‐crop vegetation areas at this time is unlikely to be a driver of pest pressure for this economically important crop.