A new way for farmers to control insect pests

SALINAS
July 11, 2012 6:56am

A fumigant called phosphine is more effective at controlling insects when it's combined with oxygen, according to findings by a U.S. Department of Agriculture scientist. The oxygen-phosphine combination could be an environmentally friendly alternative to methyl bromide for combating pests on harvested fruits and vegetables.

Methyl bromide had been widely used by California growers, especially strawberry growers, but is being phased out because of the damage it’s suspected of causing to the ozone layer.

Entomologist Yong-Biao Liu with USDA's Agricultural Research Service in Salinas has found that oxygenated phosphine fumigation effectively controlled several insect pests during laboratory studies.

Phosphine has been used for more than 80 years as a fumigant to control pests in stored products. It acts slowly against insects. Many insects, especially at egg and pupal stages, are very tolerant of phosphine, and it may take more than 10 days of fumigation treatment to control them. The new treatment would help speed up this process and control insects more quickly.

In the ARS Crop Improvement and Protection Research Unit at Salinas, Mr. Liu tested phosphine fumigation under high levels of oxygen against four pests: western flower thrips adults and larvae, leafminer pupae, grape mealybug eggs, and Indianmeal moth eggs and pupae. The four species represent insect types and life stages for which quarantine treatments are needed.

“It is important to test the fumigation on eggs and pupae because, in general, eggs and pupae are more tolerant of phosphine than larvae and adults,” says Mr. Liu. “If we can control insects at the egg and immature stages, we can be sure adults will also be controlled. These insects eat, and thus damage, produce while they are in the larval stage, but all stages require quarantine treatment.”

In 5-hour fumigations with 1,000 parts per million of phosphine at 41 degrees Fahrenheit, control of western flower thrips on lettuce increased from 80 percent to 98 percent when oxygen was increased from 21 percent to 40 percent. When the oxygen level was increased to 80 percent, 99 percent of the western flower thrips were killed.

Western flower thrips are a common pest of fruits and vegetables in the United States and are often found on fresh products exported to Taiwan, where it is a quarantined pest. Currently, fresh fruits and vegetables exported to Taiwan are fumigated with methyl bromide to control western flower thrips, but use of methyl bromide is being phased out due to environmental concerns.

Comments on this story

Carolyn O'Donnell 7/11/12 11:29 AM
California strawberry farmers largely use fumigants to inject into the soil to control plant diseases and pests in the soil. This research was not targeting soil fumigation applications that are effective at controlling plant-destroying fungus species that attack through the roots. It will only benefit the relatively small amount of strawberry exports to countries requiring fumigation.

Ron Idol 7/13/12 10:51 AM (ron.idol@airliquide.com)
40% oxygen is going to represent a fire and explosive risk and 80% just makes it worse. Any storage facility used for oxygen flushing is going to have to be specially constructed to meet a much stricter code. In addition, achieving a 40% oxygen percentage inside a storage facility is going to require a controlled atmosphere rated unit that is also designed for the fire risk. The information is very interesting but a rigid and very informed risk assessment and an economic assessment should be performed as well.