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Erratic Weather May Cause Pest Pressure

Brent Murphree

Brent Murphree

Western cotton producers and pest control specialists are staying alert for changing field conditions because of this season’s erratic weather patterns and continued water concerns in the region.

In California, early season cotton was subject to pressures that are not typically a widespread problem in that state.

“It’s been a strange early season with some early, widespread armyworm damage,” says Bob Hutmacher, Extension cotton specialist and director of the Westside Research and Extension Center in Five Points, Calif.

“It has hit plants in quite a few fields very hard, resulting in damage to terminals that in the worst cases nearly kills plants, but in all cases weakens plants and slows growth. This year is unusual in that this has been seen in quite a few fields, with damage over scattered locations.” Hutmacher points to “weird” weather and a different crop mix because of drought conditions in the San Joaquin Valley, contributing to difficult early growing conditions.

An early warming trend influenced several producers to plant cotton earlier than normal, but when several cool weather systems prevented the cotton from growing vigorously, it became vulnerable to armyworm damage and thrips.

Carol Sutherland, Extension entomologist at New Mexico State University, saw the same kind of conditions for New Mexico cotton. “The hot-cold-hot weather systems put cotton growth in a holding pattern for pests,” she says.

In New Mexico, thrips took advantage of stalled seedling growth, affecting a portion of the new crop. Arizona has fared a bit better with warmer temperatures and no major pest outbreaks.

“I’ve seen some cotton with minor damage,” says Randy Norton, regional Extension specialist with the University of Arizona, “but not anything that required treatment.”

He believes that some of the damage may be attributed to wind as several weather systems have moved through the state.

Keeping An Eye On Pest Thresholds
western reportIn all three western states, cotton pest specialists are encouraging producers to be aware of thresholds so that no single pest gets out of control.

The presence of safflower plantings in the San Joaquin Valley (SJV) can also bring with it the potential for lygus movement into cotton as the safflower matures for harvest. If safflower is harvested too late, lygus can move into cotton that is setting bolls and damage it at a critical time.

According to Hutmacher, most longterm producers, who have safflower and cotton fields, understand the timing and are well aware of this important issue with safflower as a “neighbor” to cotton fields.

But, those producers who have moved to safflower production recently because it is a hardy crop during drought need to know that there is risk associated with lygus movement.

Even though overall pest pressure may be lighter in these very dry years, when cotton is an attractive food source, lygus can target cotton.

Controlling Whitefly
According to Hutmacher, University of California Cooperative Extension expects to work with industry representatives to discuss potential whitefly and aphid management strategies for the 2015 SJV crop. Two recent seasons with significant whitefly pressures have convinced the industry to continue successful management strategies.

By identifying whitefly thresholds and maintaining treatment benchmarks, whitefly was easily managed in the West for more than 20 years.

Brent Murphree is the Cotton Board’s Regional Communication Manager for the West. Contact him via email at bmurphree@cottonboard.org.