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White grub occasional corn pest

The white grub is an occasional pest of corn that has caused significant problems across the Southern Blacklands in only two years out of the past 21, says Dale Mott, Texas A&M entomologist.

“Usually, they are less numerous and not so widespread (as Mexican corn rootworm?). Consequently, growers should not base their pest management strategy on this pest, unless they know it will be a problem.”

Many species of white grubs attack corn. Some have a one-year life cycle; others two-years. Adults lay eggs sometime in the spring or early summer and the larvae hatch and begin feeding. They remain in the ground through the winter and are generally large in size when the corn is planted.

Growers should look for white grubs in the soil in the spring prior to planting. “If grubs are common, check to be sure your at-planting time insecticide is labeled for white grub control and use the full rate,” says Allen Knutson, Extension Entomologist with Texas A&M.

The large size complicates control, Mott says. “The large grubs and the small size of seedling corn can mean severe stand loss and/or stunting to young plants. Their large size also makes them very difficult to manage with insecticides. We've seen all insecticides succumb to heavy white grubs populations.

“Some products provide better control than others, but none are foolproof against grubs. And some do well against grubs but not against chinch bugs or maybe even Mexican corn rootworm.”

Because of inconsistent control and the sporadic nature of the white grub complex, selecting a chemical that provides great grub control but may leave farmers vulnerable to other, more prominent or more damaging, insect pests, would be hard to justify, Mott says.

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