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White Heads from Wheat Stem Maggot (07/20/17)

IPM scouts detected an unusually high percentage of white heads that were damaged by the wheat stem maggot, Meromyza americana.

White Heads from Wheat Stem Maggot

IPM scouts detected an unusually high percentage of white heads that were damaged by the wheat stem maggot, Meromyza americana. However, damaged wheat heads were only observed in 11% of wheat fields scouted last week and higher percentages (>10%) of white heads were observed in Barnes, Benson, Burke, Lamoure, Mountrail, Sargent, and Towner counties of North Dakota. Female flies deposit their eggs on the leaves or stems of grasses in June. The young maggot (headless and legless larva) crawls down beneath a leaf sheath and tunnels into the stem. The stem is partially severed causing the head to turn white and it can be easily pulled out due to the maggot chewing on the stem internally. This damage becomes evident after flowering. The average percentage of white heads was only 5.6% and this level of damage is typically not an economic concern. However, the percentage of white heads observed in counties with a higher incidence was 14 to 54%.  Neither scouting or economic thresholds have been developed for wheat stem maggot. The insect also infests bluegrass, timothy, quackgrass, slender and western wheat grass, wild barley, bromegrass, green and yellow foxtail and bluestem grass.

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Janet J. Knodel

Extension Entomologist

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