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Sunday, October 24, 2021

UC Davis greenhouses fumigated for destructive rice pest

In cooperation with federal, state and county agencies, UC Davis has taken drastic action to safeguard the university’s ongoing rice research and California’s rice industry by ridding its greenhouses of a new and destructive pest – the panicle rice mite.

The microscopic mites, which are not native to the U.S., infested breeding facility greenhouses and rice fields in Arkansas, Louisiana, Texas and New York during the summer of 2007. The latest infestation was discovered in 11 UC Davis campus greenhouses in January this year, and is the first reported case in California and the western U.S.

The mites feed on developing rice grains and leaf sheaths on rice plants, and transmit fungal diseases that cause blight. They can spread by hitching on clothing, equipment or rice seeds, and have reportedly caused major damage to rice crops in other countries where they have been found.

Although the tropical exotic mites are unlikely to gain a stronghold in the Sacramento Valley’s dry climate, the university is not taking any chances to let the pest slip into the state’s estimated 550,000 acres of rice fields near Sacramento, which are valued at close to $1 million in terms of farm gain value, said Michael Parrella, an entomology professor and associate dean of agricultural sciences in the College of Agricultural and Environmental Sciences.

“[The infestation] appears to be confined to the greenhouses, and my hope is that we have eliminated the mite from those greenhouses now,” he said.

With approval and support from the U.S. Department of Agriculture, the California Department of Food and Agriculture, and the Yolo County Agricultural Commissioner, the university developed and implemented a plan to disinfect the greenhouses on Mar. 1.

Rice plants necessary for continuing research were fumigated with mite pesticide, removed from the greenhouses and securely transported to UC Davis’ Contained Research Facility where they will be preserved under quarantine until their seeds can be harvested and sterilized to kill residual mites. Remaining plants were destroyed using high heat; the greenhouses and the rest of their contents were steam-sanitized.

The greenhouses will remain vacant until the start of the state’s rice planting season on Apr. 1.

Since rice fields are not near the greenhouses, chances are low that rice mites have spread beyond campus, according to Animal and Plant Health Inspection Service program manager Andrea Simao.

Even with statistics on their side, pest management experts advise growers to take precautions to ensure their rice is mite-free.

“We will be on the lookout for this pest this growing season,” said Larry Godfrey, a UC Davis entomologist involved with the UC Statewide Integrated Pest Management Program. “Educating and having all the growers and pest control advisors look for it will leverage our efforts.”

Natalie Hummel, an entomologist from Louisiana State University Agricultural Center who helped develop USDA guidelines for inspecting rice fields, says the panicle rice mite infestations in her state during 2007 dwindled away in the winter and did not return the following year.

“After the mite was detected in Louisiana, we developed and delivered a multi-tier educational program … on scouting for mite,” she said. “Trained eyes and feet on the ground will allow us to detect [the pest] early.”

While there are no management plans or pesticides approved for general use in the U.S. to target panicle rice mite, the USDA has established guidelines to keep the pest from entering the country.

It is not known how rice mites got into the UC Davis greenhouses, but the campus will strive to prevent future infestations by developing and enforcing additional standards for researchers who handle rice plant material, Parrella said.

The affected greenhouses were used by UC Davis researchers for developing and cultivating new varieties of rice plants that can better tolerate drought, flooding and salty soil conditions to improve rice production throughout the world.

ELAINE HSIA can be reached at campus@theaggie.org.

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