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New Mexico State University

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White Grubs Hit Rebounding Winter Wheat Crop

CLOVIS - Eastern New Mexico's winter wheat producers are being bugged by grubs, those slimy, creamy white larvae known for their big mouths and bigger appetites.



White grubs, the larvae form of June bugs, are starting to pop up much more frequently this fall in Eastern New Mexico winter wheat fields, said Mark Marsalis, an agronomy specialist at New Mexico State University's Agricultural Science Center at Clovis. Cool temperatures and above normal rains aided the pest buildup. (10/13/2004) (Courtesy Photo by Matt Montgomery)

"We're seeing poor stand establishment at several locations in Curry County," said Mark Marsalis, an agronomy specialist at New Mexico State University's Agricultural Science Center at Clovis. "Some fields have a patchy appearance with large areas of either no seedling emergence or seedlings that died soon after emergence."

Grub growth is linked to cooler than normal late summer and early fall temperatures, along with above normal rain, which have produced prime soil conditions for wheat diseases and insects, he said.

The inch-long grubs are usually curled in a C shape. Their heads are brown. In late fall, the newly hatched grubs burrow to about 18 inches below soil to survive the winter. As the weather warms in the spring, they begin their journey toward the surface to feast on wheat roots.

"White grubs are the larval stage of a very common insect, the June bug," Marsalis said. "They're the brown adult beetles so attracted to bright light at night during the summer months."

According to New Mexico Agricultural Statistics Service, this year's winter wheat crop is estimated at 7.8 million bushels, a whopping 86 percent increase over last year. Drought pounded the 2003 winter wheat crop when 500,000 acres were planted but only 140,000 acres were harvested. This year producers planted 490,000 acres, and the harvested acreage is expected to soar to 300,000 acres.

Along with white grubs, Marsalis has seen increased levels of seedling blight, a fungal disease. Seedling blight can contribute to problems later in the season, including crown and root rot, he said.

Farmers still have a few options, though, Marsalis said. Seed treated with a fungicide will significantly reduce the chance of disease, especially when used to reseed damaged areas, Marsalis said.

"Unfortunately, post-damage control for seedling blight and white grubs is difficult," he said. "One recommendation is to replant when soil temperatures are low enough that grub populations are reduced."

Prevention is the key to controlling many of these problems, especially when weather conditions favor insects and disease, Marsalis said. Crop rotation is suggested to interrupt the grub lifecycle and reduce the potential for high populations, he said.