SIMULATION OF GENERATION TIMES OF THE RUSTY GRAIN BEETLE, CRYPTOLESTES-FERRUGINEUS, IN FARM-STORED GRAIN IN THE CANADIAN PRAIRIES, 1952-1990

The number of potential annual generations of the rusty grain beetle, Cryptolestes ferrugineus, was simulated in wheat stored in granaries f or all crop districts in the prairie provinces of Canada each year fro m 1952 to 1990 using a population dynamic model driven by ecological v ariables. Granary size was assumed to be 6 m in diameter. Historical d ata for temperatures at harvest and times when storage began were used in the simulation model. A second model, which predicted the rate of temperature change at the centre of a 6-m-diameter bulk of wheat, dete rmined environmental parameters for the population dynamic model. (Gra in moisture content was assumed constant at 14.5% wet mass basis.) The combined model shows that the initial storage temperature is the most important factor responsible for predicting the number of generations and levels of infestation of C. ferrugineus. This finding was largely validated by historical grain storage and infestation data. For vario us years initial grain temperature ranged from 17.7 to 37.4 degrees C and harvest dates were between 1 August and 20 October. The number of generations annually in simulations based on field conditions ranged f rom 0.35 to 6.77 with a mean of 3.29. Three or more generations result in a severe infestation and every year at least three simulated gener ations were completed in some crop districts. In one year, at least th ree generations were completed in every crop district. Harvest tempera ture and date permit prediction of crop districts that will potentiall y have the largest populations of C. ferrugineus so that early monitor ing of wheat for infestations can be targeted to areas most at risk.