Cabbage, broccoli may hold key to spider mite control

Tuesday, January 28, 2014

By JIM ALGIE

Genome sequencing of the spider mite led by University of Western Ontario researchers has identified a potential, biological control based on naturally-occurring properties of the plant family, brassicaceae.

But commercial development of the idea for use in agriculture may be slow, researcher Vojislava Grbić said, Monday, in an interview from her London, Ont. office. Because the chemicals involved are relatively well-known in scientific literature, they are not likely patentable, a disincentive for any commercial developer, Grbić said.

A paper published recently in the journal Plant Physiology by three Western scientists and a group of international associates describes the toxic effect on spider mites of chemicals in Arabidopsis thaliana. It’s a small, flowering plant native to Europe.

It’s also a member of the brassicaceae plant family which includes cabbage and broccoli, all of which produce self-defensive substances known as indole glucosinolates. The Plant Physiology article describes interactions between plant and spider mite genomes and identifies the toxic effect of indole glucosinolates on mites.

The discovery “holds potential for developing alternative, pest control strategies against this pest that are environmentally safe and consumer friendly,” Grbić says in a university-issued statement. In a recent interview, however, she said it’s not clear precisely how the natural defense system of brassicaceae can be adapted commercially for use in agriculture.

A biologist, Grbić is part of the team responsible for sequencing the spider mite genome. She and her colleagues are mainly interested in the adaptation process by which the insects develop pesticide resistance. Their continuing lab work will concentrate primarily on ways by which mites seek to resist plant-produced glucosinoids.

Grbić figures, however, that sprays or transgenic crops incorporating glucosinoids could help safely control spider mites, one of agriculture’s most persistent, widespread pests.

“I would say that glucosinoids in general are very potent,” Grbić said. “Unfortunately pests have to ingest them; so the pests need to feed on a surface that has it. So either the plant produces it or it has to be sprayed on.”

The Western group is focussed on basic biology but would welcome input from growers about mite control issues in Ontario. Because glucosinoids in brassica are relatively well-known in science, they are not likely patentable. Consequently, it may be hard to find commercial development, Grbić said.

“The problem in this field is not the question of whether or not there is a cure. The question is whether you can get money out of it and because you potentially cannot, people are not pursuing it commercially,” she said.

“For any commercial application, unfortunately, we have to come up with a novel molecule,” Grbić said. “What is now being plant produced is no longer profitable,” she said.

She has found experimental attempts to develop brassica cover crops as a means of controlling soil nematodes in tomato plants. But they produced “mixed results,” Grbić said.

“If growers have experience with spider mite infestation or a problem controlling it, we would appreciate hearing back from them,” Grbić said.

“We’re developing a lot of tools that should make us quite powerful following the basic biology,” she said. “It would be good to understand what are the current problems Ontario and Canadian farmers face in regard to spider mites,” Grbić said.

To reach Grbić, email vGrbic@uwo.ca. BF