Big pest, small genome: Blueprint of spider mite may yield better pesticides

Scanning electron microscope image of a two-spotted spider mite, which is less than one millimeter long. Richard Clark of the University of Utah helped lead an international team of 55 scientists who deciphered the genome of the two-spotted spider mite in a paper published in the Nov. 24 issue of Nature. Credit: Nature, Vladimir Zhurov, University of Western Ontario

The voracious mites, which technically are not insects, can eat more than 1,100 plant species – a rare trait. The mites' newly revealed and sequenced genome contains a variety of genes capable of detoxifying pesticides as well as toxins plants use to defend themselves, the scientists report in the Thursday, Nov. 24 issue of the journal Nature.

"One key thing that makes spider mites unique is they can eat many, many different plant species," says Richard M. Clark, one of five main authors of the study and an assistant professor of biology at the University of Utah. "These mites are often house plant pests – a major cause of people's house plants turning yellow and getting sick. They also are a major problem for agricultural nurseries and greenhouses, and for field crops."

Primary targets are tomatoes, peppers, cucumbers, strawberries, corn, soybeans, apples, grapes and citrus.

Clark says the new study's "importance is largely in understanding how animals eat plants, with the long-term goal of developing effective ways to prevent crop damage from mites and insects. If we can identify the biological pathways mites use to feed on plants, we can potentially identify chemical and biological methods to disrupt those pathways and stop the mites from feeding."

The two-spotted spider mite, which is no more than 1 millimeter long, "is a major global pest, and is predicted to be a growing concern in a warming climate because they multiply extremely fast at high temperatures – 90 degrees Fahrenheit or more," he adds. "They do really well in hot and dry climates like Utah."

Yet, the two-spotted spider mite "has been found to rapidly develop resistance to multiple types of pesticides, often within a couple of years after a pesticide is introduced," says Clark. "It is resistant to many common pesticides used against insects."

The Nature study deciphering the genome of Tetranychus urticae, the two-spotted spider mite (which has two red spots), was conducted by an international research team of 55 scientists from North America, Europe and South America.