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Research advances reduce lygus damage in cotton

University of California researchers from left Pete Goodell Carol Frate Shannon Mueller and Larry Godfrey
<p> University of California researchers, from left, Pete Goodell, Carol Frate, Shannon Mueller, and Larry Godfrey.</p>
University of California research has placed the lygus bug squarely in prevention crosshairs to help cotton producers reduce yield loss and keep greenbacks in their wallets. &ldquo;It takes a village&rdquo; (an agricultural community) to better manage lygus, says Pete Goodell, UC IPM Cooperative Extension Advisor. Effective lygus management involves landowners, producers, pest control advisers, biological and physiological experts, and others. Major risk factors for lygus movement include distance, strength, timing, and landscape configuration.

For more than 50 years, the University of California has placed the lygus bug squarely in prevention crosshairs with research aimed to help producers reduce yield loss in cotton and keep greenbacks in their wallets.

This effort is tied to the California birth of the integrated pest management program in 1959 where four UC entomologists adamantly agreed that effective pest control strategies should include reduced insecticide use or none at all when possible.

The journey to control lygus in Western cotton fields has created opportunities for producers. A variety of pest management tools ranging from natural predators to strategic crop placement are reducing the lygus march into cotton.

The bottom line is each producer in a cotton-growing community should work together to reduce the factors which spur lygus development and movement into cotton.

“It takes a village to manage lygus,” says Pete Goodell, UC IPM Cooperative Extension advisor with the UC Statewide IPM Program. “Effective lygus management involves landowners, producers, pest control advisers, those with an expertise in biological and physiological issues, and others.”

“Working together across the local landscape is an effective way to effectively manage lygus to reduce its impact in cotton.”

Goodell shared this village mantra during his keynote address at the 3rd International Lygus Symposium held in Scottsdale, Ariz., in late November. He shared California’s success stories on lygus strategies with the 80-plus attendees from 12 states and five countries.

Two species of lygus are found in California’s San Joaquin Valley — Lygus hesperus and Lygus elisus. Hesperus represents about 90 percent of the lygus. Immatures and adults of both species can damage cotton.

Lygus Hesperus is a native insect with a wide host range. The bug overwinters as an immature adult, produces five generations per year, and reaches maturity in 21 days during the summer months.

Lygus typically emerge in late December to feed and begin the reproductive process.

Lygus is a pre-floral feeder and removes the cotton plant’s developing floral bud usually around June. The plant works to replace the bud loss which in turn slows plant development and reduces yield.

The worse outbreak of lygus in California cotton dates back to 1978.

“The outbreak was an absolute disaster,” Goodell told the group. “It was one of the few times where you could see yield reductions directly attributed to lygus.”

Professor Vernon Stern of UC, Riverside, one of the four fathers of the integrated control concept, learned that most cotton arthropod populations must rebuild each year. Surrounding cropping systems determine the degree of pest build up.

Some crops and weeds serve as a source or sink for lygus, or both. The primary hosts for lygus include cotton, safflower, alfalfa, alfalfa seed, and weeds.

Lygus risk factors

“Unmanaged safflower is a source of lygus and a very high-risk crop to cotton,” Goodell explained. “For safflower planted near cotton, it’s important to treat safflower with insecticide to reduce pest numbers before the insect moves into cotton.”

The California Department of Agriculture reports about 53,000 acres of safflower were grown in California in 2011, mostly for oil for biofuel.

Goodell’s UC IPM career began in 1981. He initiated lygus surveys to estimate lygus population buildups in the SJV West Side foothills during the spring months before the insect’s mass movement to the east into farm fields.

In 2009, Goodell and other entomologists tapped satellite remote sensing technology to develop maps of lygus movement from the foothills. The system worked fine when skies were clear. However, cloudy days prevented satellite cameras from seeing the ground to take photos so the effort was abandoned.

Entomologists utilize short- and long-term weather forecasts to help predict lygus numbers. An El Niño wet winter weather pattern can deliver a greener landscape and higher lygus numbers. A La Niña winter keeps the foothills brown with less food for insect development.

Goodell chuckled and said, “When the hills are brown, hopes abound. When green in May prepare to pay.” The analogy drew laughter from the crowd. 

The major risk factors for lygus movement, Goodell said, include distance, strength, timing, and the landscape configuration.

There is an inherent limitation on how far a lygus bug can fly since it is not considered a long-distance flyer. Strength pertains to the condition of the host source. 

“Distance and strength are interrelated,” Goodell said. “If you have a strong source and the cotton is close by then this will increase the risk versus the strong source being further away.”

Timing involves when a crop or weed host releases the insect. If the source is harvested earlier than cotton, lygus will leave to feed in cotton.

The landscape configuration involves all crops grown in the cotton-growing area. A sink host can help absorb lygus and slow its movement into cotton.

Alfalfa can serve as a source and a sink for lygus. When alfalfa is cut, the insect marches out of alfalfa toward another host. A managed strip habitat in alfalfa can act as a sink and reduce lygus movement out of alfalfa.

These and other more detailed findings have been gained through the USDA Risk Avoidance and Mitigation Program project, or RAMP. The five-year, $2.5 million project has assisted more than a dozen researchers in California, Arizona, New Mexico, and West Texas in studying lygus biology and how their respective local landscapes impact multiple crops.

With this collective information, the next phase is getting the critical information out to cotton growers to better understand how multiple local issues impact lygus and cotton.

Over the last several years, Goodell and University of Arizona IPM Specialist Peter Ellsworth created a computer gaming software system called Lygus Simulation Training Environment. The video game allows producers and others to use computers in a meeting setting to select their crops for the next crop year and actually see the crops their neighbors intend to plant.

The software then predicts lygus outbreaks based on crop placement. Producers can readjust their planting intentions to reduce lygus numbers and help their neighbors growing cotton.

The lygus-cotton video game was developed for producers in the SJV, Arizona, and West Texas. The game can be tweaked for other areas of the Cotton Belt.

The game was tested with a group of cotton growers in Marana, Ariz., in June 2011. The Lygus Symposium took the game for a spin. Both groups gave the interactive game a thumbs up.

The next step is to roll the gaming simulation out at Extension grower meetings and perhaps online.

The gaming program has not been launched due to the lack of funding. Ellsworth and Goodell are seeking funds to place the program in the hands of growers.

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