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Invasion of the body snatchers

Grasshoppers being preyed upon by parasitic red mites

This grasshopper munching on a sunflower in southwestern Manitoba is being devoured by parasitic red mites (Eutrombidium locustarum), says Manitoba Agriculture, Food and Rural Development (MAFRD) entomologist John Gavloski.

The mites feed on the blood (hemolymph) of grasshoppers. They also prey on grasshopper eggs. Each female mite can lay up to 4,000 eggs, providing mite populations the potential to increase rapidly and substantially as grasshopper populations increase.

Research in Montana has shown that these mites can reduce the survival and reproduction of grasshoppers. Red mites are fairly common this year, Gavloski said.

Lionel Kaskiw, MAFRD’s farm production advisor based in Souris, said one in seven or 10 of the grasshoppers he saw recently in a sunflower field last week had the mites. This particular field had a high number of feeding grasshoppers on its edges. Gavloski said it doesn’t usually pay to spray grasshoppers in sunflowers until there is at least 25 per cent defoliation.

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  • Dan Johnson

    These red mites have been observed and sometimes studied in Canada since the 1930s. They have effects on individual grasshoppers, by reducing ability to fly and reducing reproductive success. (Other insects have them as well.) These mites have small but usually insignificant effects on grasshopper populations. Numbers and stages of red mites on grasshoppers were the observed each year during 1983-2003, at the Lethbridge Research Centre. Various updates and reports were made to growers and provincial agriculture departments. Other biological control agents are much more significant in impacts, although also usually moderate in result.