Population dynamics and seasonal incidence of aphids on mustard under changing climate

Abstract:

Roughly 38% of Canada’s canola-mustard output is lost each year to insect pests, with aphids ranking as the single most damaging group across the semi-arid cropping belt of southern Alberta. This research examined the population dynamics and seasonal incidence of aphid species on mustard (Brassica juncea L.) under the changing climatic conditions of southern Alberta. Field observations were carried out at the Prairie Dryland Agricultural College research farm, Lethbridge, during the growing seasons of 2022-23 and 2023-24. Weekly counts were recorded on ten randomly tagged plants per replication across three cultivars (AC Vulcan, Andante, and Cutlass). Lipaphis erysimi was the dominant species, accounting for 62.4% of total aphid counts, followed by Myzus persicae (18.7%) and Brevicoryne brassicae (11.3%). Peak population coincided with the first fortnight of July in both seasons (67.4 and 74.8 aphids per 10 cm apical shoot, respectively). Multiple regression analysis showed that maximum temperature (r = 0.78) and morning relative humidity (r = −0.45) were the strongest weather correlates. A year-on-year increase of 11.0% in peak aphid density was observed, pointing to a climate-driven intensification of pest pressure that warrants revised threshold-based management calendars.