Intent on protecting the state’s commercial rice fields from a tiny but destructive bug known as the panicle rice mite, UC Davis is decontaminating 11 campus greenhouses where the mite was recently found.

In addition, more than 400 potted rice plants will be moved to a secured growing facility on campus until the rice seed, which is critical to several important international research projects, can be harvested. The greenhouse decontamination process will be completed by March 1, at least one month before commercial rice is planted in the Sacramento Valley.

It is not known how the panicle rice mite got into the greenhouses, but the infestation was detected in January during routine greenhouse inspections. The mite initially was identified by California Department of Food and Agriculture scientists, and their findings were confirmed by U.S. Department of Agriculture scientists at the Systematic Entomology Laboratory in Beltsville, Md.

“Since the mite was identified, the campus has been working with the U.S. Department of Agriculture, the California Department of Food and Agriculture and the Yolo County Agricultural Commissioner’s office to create a plan for ridding the greenhouses of the pest,” said Michael Parrella, a professor of entomology and associate dean of agricultural sciences for the College of Agricultural and Environmental Sciences.

“We are grateful to our colleagues in those agencies for their help in developing a decontamination program that will safeguard the state’s rice fields against this invasive pest and minimize the impact on campus rice research,” he said.

“It is encouraging that this currently is a limited infestation,” said Yolo County Agricultural Commissioner Rick Landon. “We appreciate the efforts of UC Davis in working with us to ensure that the rice industry of the Sacramento Valley is protected from the rice panicle mite.”

The affected greenhouses are being used by four UC Davis faculty members and their research teams, who are working to reduce global hunger by improving the hardiness of rice plants. Their studies are focused on developing rice plants that have higher quality rice grain, produce a greater yield and can better withstand environmental stresses such as drought, salty soils and seasonal flooding.

In order to rid the campus of the panicle rice mite, all plants in the infested greenhouses will be destroyed, and the greenhouses will be sanitized.

Potted rice plants that are critical to the completion of ongoing research will be preserved under tight quarantine controls, with supervision from California Department of Food and Agriculture and U.S. Department of Agriculture personnel. Those potted plants will be placed in plastic bags within an enclosed truck and moved to the campus’s Contained Research Facility, where they will be grown until their seed can be harvested.

Those plants will then be destroyed, and their harvested seeds will be sterilized to kill any mites but preserve the seeds for use in research.

The Contained Research Facility is a Biosafety Level III agricultural research building, specially designed for securely studying exotic, or non-native, plant pests and diseases. It is the only facility of its kind in the Western United States.

All other plants in infested greenhouses will be destroyed using intense heat and pressure. The infested greenhouses, along with greenhouse pots and tools, also will be sterilized. No rice will be planted in these greenhouses for at least 30 days.

The panicle rice mite, whose scientific name is Steneotarsonemus spinki, is so small that it can only be seen with a magnifying lens. Its common name is derived from the panicle or seed head at the tip of the rice shoot, which the mite infests and deforms. The mite does not fly, but can be unintentionally transported on clothing, farming implements or infested rice seed. Infestation by the mite causes browned rice hulls and leaf damage, and sometimes transmits fungal diseases to the plant.

The panicle rice mite was first introduced to the United States in 2007 and has been found in Louisiana, Arkansas, Texas, Ohio and New York. Until the discovery at UC Davis, it had never been identified in California or elsewhere in the western United States. The mite has been particularly destructive in rice fields of tropical regions of Asia, specifically China and Taiwan, as well as in the Caribbean and Central America.

“It is not known whether the panicle rice mite can even survive Northern California’s cold winters; nevertheless, we are taking every precaution to ensure that the mite does not move beyond our greenhouses,” Parrella said.

Parrella added that the university also will conduct an internal review of existing procedures for handling rice seed brought in from elsewhere in the United States, with the goal of preventing future pest infestations.