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New Mexico State University

New Mexico State University

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Drought Conditions Complicate Range Management

LAS CRUCES -- Drought conditions could complicate ranchers' efforts to manage locoweed and mesquite this year, said a New Mexico State University range brush and weed specialist.

"With the drought, just about the only green herbaceous plant on the range is locoweed or some other poisonous plant, increasing the likelihood of livestock poisonings," said Keith Duncan with NMSU's Cooperative Extension Service.

Precipitation in New Mexico was 60 to 80 percent below normal for the first four months of 1996. This follows two to three years of severe drought in the state.

Several poisonous plants stay green throughout the winter and/or germinate in winter or early spring. This means that whatever winter moisture was received is being used not by grass, but by the locoweeds and other poisonous plants such as groundsel or desert baileya, he explained.

Lack of rainfall, resulting in little to no grass growth, exaggerate the poisonous plant problem on rangeland. "Hungry livestock search out green plants to eat, even if the plants are poisonous," Duncan said.

Extension range specialists have been receiving calls for several months concerning locoweeds and other poisonous plants. "In dry years, management of locoweed becomes more critical in the maintenance of livestock herds," he said. "Feeding programs, including supplemental feeds, are important in reducing the effects of poisonous plants."

"Spray programs also may be helpful in reducing the incidence of poisonings, but they may not be the best management option in severe drought conditions," he added.

Extreme weather conditions tend to speed up the plants' maturity process, which results in less time that plants are susceptible to herbicides.

This year, ranchers also are dealing with how to manage mesquite. Although spraying to control mesquite normally begins in mid-to late June in most parts of New Mexico, 1996 might not be a very good year for it, Duncan said.

"The very dry conditions across New Mexico will likely lead to decreased levels of control this year," he said.

Normally, the best time for spraying is 45-90 days after bud break, with soil temperature at a 12-18 inch depth of 78-86 degrees.

"But mesquite plants need to be in good condition when sprayed in order to obtain the best results," Duncan said. "When plants are stressed, such as by drought conditions, the herbicide is not absorbed into the plant nor taken up as it should be. The result is a disappointing spray job."

Drought is not the only factor which affects how well spraying works, he added. Leaf damage due to insects or hail can decrease mesquite control.

Also, the high air temperatures and wind speeds that have prevailed throughout New Mexico for several months decrease the effectiveness of spraying. These conditions slow growth of mesquite and put a thicker wax coat on the leaves sooner than normal.

"Ranchers should think carefully about their alternatives, especially with this year's high feed bills, little or no grass and extreme weather conditions," Duncan advised.

For more information on rangeland spray programs or locoweed management and control recommendations, contact your local county Extension office.