Air trajectory model applied to an in-depth diagnosis of potential diamondback moth infestations on the Canadian Prairies.
Diamondback moth caused significant damage to the canola crop on the Canadian Prairies in 1995. This infestation caught farmers and agriculture agencies off guard and led to a joint initiative by Agriculture and Agri-Food Canada, Canola Council of Canada, and Environment Canada to determine if such infestations could be forecast. The diamondback moth rarely overwinters on the Prairies and must be advected with air currents from source regions far to the south. A network of pheromone trap sites was established across the agricultural areas of the Prairies in 1997 and 1998 and backward trajectories were generated by the Meteorological Service of Canada's Canadian Meteorological Centre (CMC) for these locations. Forward trajectories were produced from a number of potential source regions. The trajectories were examined to determine if they could explain the occurrence of diamondback moths in the traps. Some aspects of the observed moth populations in these years were successfully explained by backward trajectories that passed near the surface over southern Texas about four days prior to arrival over the eastern Prairies. The trajectory analysis failed to explain moth populations in Alberta. Forecast trajectories from potential source regions based on the Meteorological Service of Canada's Global Environmental Multiscale (GEM) model were occasionally successful as a predictive tool. The frequency of back trajectories from several locations across the southern Canadian Prairies for the summers of 1997-1999 demonstrated that very few originated in or crossed the potential moth source regions in Texas, California or Mexico. Used in conjunction with the network of moth trap sites, the backward trajectories were helpful in providing early detection of diamondback moth infestations.