Fighting the Bugs that Bug Flower Growers

Wendy Romero’s research nets award from biological control group

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Wendy Romero

Master's student Wendy Romero

Testing greener ways to keep bugs from damaging flowers could help Ontario greenhouse growers, retailers and customers; it’s already helped Wendy Romero. Studies by the M.Sc. student in the School of Environmental Sciences (SES) have earned her this year’s outstanding master’s student award from the International Organization for Biological Control (IOBC).

Romero studies non-chemical and reduced-risk chemical controls for western flower thrips and silverleaf whiteflies that hitchhike into greenhouses on cuttings used to start new plants. Such cuttings often arrive in Canada infested from overseas. Many flowers sold in Ontario come from around the world, including Central America ─ also home to Romero, who grew up in El Salvador.

Working in the Bovey Building lab of her supervisor, Prof. Cynthia Scott-Dupree, and in the adjacent greenhouse, Romero tests control methods for fleck-sized thrips and slightly larger whiteflies on cuttings of chrysanthemums and poinsettias. “Growers are struggling to get rid of these pests,” she says.

Canada lacks the range of chemical controls available to growers in other countries. But introducing new chemicals wouldn’t necessarily solve the problem, as the insects speedily develop resistance and because pesticide residues on cuttings could affect biological control agents in the receiving greenhouse, says Scott-Dupree.

The insects might even have become resistant in the plants’ native country, where growers routinely use many pesticides, Romero says. “Resistance is developing even before they get to Canada.”

She’s interested in offering growers a variety of non-chemical or reduced-risk chemical controls for these pests for possible use within an integrated pest management approach. Canadian growers use biological controls already, although their effectiveness varies with the size of the infestation or use of conventional insecticides.

Romero has looked at physical controls ─ mineral oil, hot water, insecticidal soap, fungus ─ and microscopic nematode worms known to prey on plant pests as a form of biological control. (Other biological controls include predatory mites and parasitic wasps.)

Looking at one treatment at a time, she found that thrips are killed when immersed in oil and hot water without ill effects to the plant cuttings. Fungus and nematodes also worked well against adult thrips but less so against immature insects. Whiteflies are particularly vulnerable to some insecticidal soap and oil immersion.

Romero says further studies might look at combinations of treatments.

Soaps and mineral oil can reduce human health risks posed by conventional chemicals applied in greenhouses. They also have low residual effects, so they don’t affect biological controls used by growers.

All of the products she’s testing are already commercially available to growers. Various fungal and nematode treatments are already available but only as sprays rather than as immersion applications.

Romero says her work might support efforts to introduce treatments or expand existing ones. “Growers are very satisfied with the results.” She has spoken at industry events, including a Flowers Canada (Ontario) pest management conference this past summer.

The Canadian floriculture industry is worth about $1.5 billion annually in farm-gate sales, according to a research document prepared by Flowers Canada Growers in Guelph. In Ontario, the industry is worth about $774 million.

Romero started her degree at Guelph in 2009 and will finish next spring. She will receive her IOBC award this semester at a meeting of the Entomological Society of America. Earlier she received an industrial post-graduate scholarship from the Natural Sciences and Engineering Research Council, sponsored by Flowers Canada (Ontario).

She studied biology in Guatemala, where she helped collect and identify thrips and confirmed infestations of flower cuttings. She says studying at Guelph has helped her learn to design experiments and think through research problems. And helping her in the lab this semester is Isabelle Thibout, a third-year undergrad on an internship from France.

Growers are the main beneficiaries of Romero’s research. But she’s provided a few tips to relatives back home. Bugs on her mom’s papaya trees? “I said: Why not try mineral oil.” It worked.