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Disease damages wheat roots, thwarts water uptake

02.03.2006

Alterations in irrigation schedules may be needed when wheat streak mosaic infection is suspected in winter wheat crops, according to a Texas Agricultural Experiment Station researcher in Amarillo.

Drought this winter has prompted more irrigation of wheat than normal; however, wheat streak mosaic is also being detected, said Jacob Price, a graduate student and diagnostic technician for the Experiment Station’s plant pathology department.

Wheat streak mosaic, the most common wheat disease in the Texas Panhandle, is a problem throughout many wheat production areas, Price said. The disease is spread by the wheat curl mite and currently no pesticides can control the mite, he said.

In the High Plains, wheat is frequently irrigated and grown for both grazing and grain production, he said. It is already known the disease has a negative impact on plant development and forage yield.

Now Price is trying to get to the "root" of the problem. He wants to determine what effect the stunted root systems of infected plants have on their uptake of irrigation water and whether different levels of irrigation make a difference on the plants’ growth and yields.

"We’re trying to determine if it is worth irrigating at all," he said.

"I hope this research will develop recommendations on irrigation for infected wheat plants."

Samples are already being submitted this year with the yellowing, stunted symptoms of wheat streak mosaic to Jacobs. After making a diagnosis, he sends the information to the Plant Diagnostic Information System, a wide-scale information system used by many agricultural centers.

"What I’ve seen in my experiments so far is it (the disease) damages root growth," he said. "Once infected, the roots don’t grow anymore. If they don’t develop, they can’t take up water efficiently and expensive irrigation water would be wasted."

Producers normally irrigate using the guidance of the Texas High Plains Evapotransporation network, Price said. The network collects weather data from various stations and uses it to estimate the daily water use of a crop.

By determining how much water the infected plants are actually taking up, he said he hopes to help producers save water and money and still maintain the best possible yields under the diseased scenario.

His study is only a year old, but Price intends to replicated it two more years both in the greenhouse and in the field. The greenhouse study looks primarily at root mass, while the field study tests plant production and yield, he said. He is using a neutron depth moisture gauge to monitor water uptake.

"When it starts warming up and the wheat starts growing, that’s when we’ll see more yellowing and we’ll get a lot more samples to test," he said.

"I’m concerned since we’ve had so much drought and it’s so expensive to irrigate this year," Price said. "Water-use efficiency is going to be key."