MISSISSIPPI STATE -- Dry conditions and aphids are challenging Mississippi's winter wheat just as the crop enters the weeks critical for growth and yield potential.

Grower interest in wheat was strong last fall coming off the record 59-bushel-per-acre average in 2006 and high market prices.

Erick Larson, small grains specialist with Mississippi State University's Extension Service, said growers planted 275,000 acres of wheat in 2006, the most in the state since 1992. Growers planted 85,000 acres in 2005.

“Frequent rainfall during the optimum wheat planting time last fall caused considerable difficulty with planting. Some growers broadcast seed from airplanes during the wet period or waited until after Thanksgiving when fields dried enough to permit standard planting methods,” Larson said. “Fortunately, we had relatively good conditions throughout the winter, which helped the wheat crop's potential.”

The crop's yields will depend heavily on weather through April to the middle of May.

“Dry weather is good for wheat up to a point, but the crop is starting to show some drought stress in places,” he said. “Wheat typically produces its highest yields during dry years, but we don't usually have drought stress in March.”

Larson said the crop needs rain to incorporate the nitrogen in the soil and progress the crop into the grain-filling and heading stages. Urea-based sources of nitrogen fertilizer lose their effectiveness if rains do not incorporate the fertilizer into the soil, especially when days are warm.

“As long as we get some rain soon, we should have a very good crop,” Larson said.

Extension entomologist Angus Catchot said two species of aphids are showing up in wheat fields across the state, with the highest populations in the Delta. Dry conditions could impact management decisions as growers debate the need to treat fields.

“We are mostly finding bird cherry-oat aphids with some greenbugs mixed in. Some research indicates that wheat can tolerate high levels of bird cherry-oat aphids without economic losses,” Catchot said. “However, greenbugs can be of serious concern when numbers reach certain levels because of the toxin they secrete when feeding.”

Catchot said growers can distinguish between the two species easily. Bird cherry-oat aphids are darker and usually have pinkish-red coloration around the abdomen, while greenbugs are light green with a faint black stripe that runs down the middle of the body.