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Fully selective insecticides preferred for lygus, whitefly control in low desert cotton

Peter Ellsworth is the last man standing; the lone remaining researcher in Arizona conducting cotton insecticide research trials.

For 18 years the University of Arizona (UA) integrated pest management specialist has endured sizzling hot summer days in the low desert while diagnosing insecticide effectiveness. The 22-acre trials are located at the UA’s Maricopa Agricultural Center, “the Big MAC,” in Maricopa, Ariz., about 30 miles southwest of Phoenix.

A major focus of Ellsworth’s research is side-by-side comparisons of current insecticides on the market and products under development. Ellsworth is comparing new, potentially selective products that provide effective lygus (Lygus hesperus) and whitefly (Bemisia tabaci = B. argentifolii) control that don’t harm natural predator bugs; such as the big-eyed bug, minute pirate bug, assassin bug, damsel bug, and ladybird beetle.

While many broad spectrum insecticides including acephate, endosulfan, and Vydate (DuPont) are effective against lygus and whitefly, this approach can reduce “good bug” numbers.

“Conserving natural insects is essential,” Ellsworth says. “Killing the natural enemies leaves the battlefield devoid of our infantry out there working all the time on the grower’s behalf.”

Ellsworth shared his trial results during a late season cotton field day at the Big MAC in September.

Lygus control

Major technological strides in recent years have brought new fully selective products to the market.

“Several years ago we identified Carbine as the first very effective and virtually fully selective lygus insecticide available to cotton farmers,” Ellsworth said. Carbine, from FMC, is registered across the Cotton Belt.

“Carbine kills lygus, plus is an excellent aphicide,” Ellsworth said. “However, Carbine doesn’t harm the key natural enemies.”

Over the last several years many Arizona cotton growers have switched from broad spectrum products to Carbine, Ellsworth says. “While lygus numbers were low in cotton in 2006 and 2007, growers said Carbine did a great job combating existing populations and helped control this year’s population without causing costly secondary pest outbreaks.”

Ellsworth gave rave reviews on BAS320, or metaflumizone, from BASF. “This product is quite effective.” The yet-to-be-named product could be on the market for the 2009 cotton crop year.

Carbine and metaflumizone offer growers the option to “marry” selective pest control approaches, Ellsworth says, including Bt cotton plus selective chemistry for lygus and whitefly control.

“This is the 1-2-3 punch for Arizona cotton growers who fight against three pests; pink bollworm (currently under eradication), whitefly, and lygus,” Ellsworth said. “The three selective technologies can allow a grower to get through an entire season without ever using a broad spectrum insecticide. It will reduce his overall need to spray, protect yields, and contribute to a better environment.”

Whitefly control

Ellsworth’s research on insecticides for whitefly control has spanned over a dozen years. When he asked growers, pest control advisors, and others at the field day which whitefly product was the most popular, most shouted Intruder (DuPont).

Ellsworth’s cotton whitefly guidelines place insecticides into three categories: fully selective, partially selective, and broad spectrum. “Intruder falls in the partially-selective box which is good,” Ellsworth said. “Intruder is incredibly effective against all stages of whitefly. It’s not as selective as Knack, Oberon, or Courier, which can be considered fully selective. Intruder is very popular with growers.”

The only concern with a widely-used product, Ellsworth says, is the potential for pest resistance down the road.

Other good whitefly controls include Oberon (Bayer). Movento, a Bayer product under development, is an extremely effective material, Ellsworth reports, not only for whitefly, but how Movento moves up and down the plant. Some insecticides applied to the plant penetrate the leaf and go no further, or penetrate leaves and stems and then move upward. Movento is fully systemic; it efficiently moves up and down the plant.

“When spraying 4 to 5-foot low desert cotton plants in mid-to-late season, it’s good to know that we may have a product (Movento) to apply even by air that can hit the plant tops and penetrate the canopy,” Ellsworth said. “The actual chemical movement inside the plant facilitates movement throughout the plant.”

He says Bayer has decided to bring Movento to the cotton market, in part because of the successful demonstrations of its efficacy in trials like Ellsworth’s.

Another whitefly product with good marks is NNI0101 by Nichino America, Inc. Like Movento, NNI0101 has a different chemistry unrelated to other products on the market. This is critical to resistance management. NNI0101 is less selective.

Ellsworth says there’s still a place for broad spectrum insecticides in cotton when the pest spectrum is wide and the pressure is high.

Ellsworth’s research results provide beneficial information to growers in Arizona, Southern California, New Mexico, West Texas, and northern Mexico. He says insecticide use has substantially decreased in Arizona cotton over the past decade. From 1995 to 2006 about 1.7 million fewer pounds of insecticide active ingredient were used.

“The products used in 1995 were applied in pounds per acre where today insecticides are applied in ounces or even milliliters per acre,” Ellsworth said. “A teaspoon or tablespoon can effectively treat a football field of cotton.”

In additional cotton trials, Ellsworth and other researchers have played a major role in developing transgenic plants for pink bollworm “pinkie” control.

A regional ecology project with Ellsworth as the lead, along with cooperators in California, West Texas, New Mexico, and Arizona is aimed at better understanding the movement and distribution of pests and natural enemies. The goal is creating an environment where growers can intelligently design the agricultural landscape to minimize the attractiveness to pests and maximize the movement, use, and utility of natural enemies.

Agricultural research requires sufficient dollars and generally there’s not enough dollars to fully support it. While the UA provides salary funding for Ellsworth and a technician, plus a truck, all research funding is secured through grants, contracts, and gifts. These dollars cover expenses ranging from a sprayer to truck fuel and a team of technicians and summer staff that help conduct experiments and collect data. This is fairly typical at most land-grant universities today, Ellsworth says.

California cotton

Whitefly pressure in California cotton fields was slightly heavier this year than average, according to Pete Goodell, IPM advisor, University of California, Davis. Pressure was more widespread in Kern County.

Lygus numbers in cotton were about average except for high populations in the Five Points area. “Lygus in the Five Points area was devastating; the worst lygus I’ve seen in my 35 years in cotton fields,” Goodell said. The lygus increase was “landscape mediated,” caused by the impact of reduced cotton acreage combined with increased safflower acres. Safflower is a major host for lygus.

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TAGS: Cotton
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