Integrated management of crop pests–abundance of wheat midge and its parasite in different management systems
Populations of wheat midge larvae and parasite larvae were assessed in six management systems at Kernen Farm near Saskatoon in 1997-1999. Ten soil cores were collected from each plot in mid May and late June. Emergence cages were placed in wheat plots in 1997 and canola plots in 1998-2000 to monitor emergence of adult wheat midge and parasite. Wheat plots were inspected in the evening to estimate numbers of wheat midge during heading and anthesis. In 1997, wheat midge populations exceeded one midge per 4-5 wheat heads during heading and were controlled with chlorpyrifos. Adult populations were below the economic threshold in 1998, 1999 and 2000. Results showed that emergence of adult wheat midge and parasites differed in management systems. Emergence of each species was 1.4-2.0 times higher in early-seeded systems than in late-seeded systems and 1.5-2.0 times higher in zero-till systems than in tilled systems. Late-seeded management systems with high tillage had the lowest emergence of adult wheat midge and parasite. Wheat production on the same land for two consecutive years should be discouraged in zero-till systems to deter buildup of wheat midge populations. Emergence of adult wheat midge and female wheat midge varied greatly from year to year. Emergence was 4-10 days earlier in 1997 and 1998 than in 1999 or 2000. In 1997-2000, dates for 10%, 50% and 90% emergence were July 10, July 19 and July 25, respectively. Degree-day requirements for 10%, 50% and 90% emergence of adult wheat midge were similar with air temperatures (706, 811, and 894 degree-days, respectively) and soil temperatures at 2.5cm depth (706, 817 and 906 degree-days, respectively). Accumulated degree days, based on AES air temperatures or hourly soil temperatures at 2.5cm and 5.0cm depths, provided a reliable method of evaluating emergence of adult wheat midge.
crop management systems
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