New pest control tools developed at Grbic Lab could prove ‘mite-y’

Spider mite populations in greenhouses can quickly grow and wreak havoc on plants. Western University’s Grbic Lab is working on better understanding spider mite species, resistance to pesticides and developing tools to help growers more quickly and efficiently deal with the pest. ~ Gilles San Martin photo

By Luke Edwards

As the old saying goes: don’t bring a knife to a gun fight. But if you don’t know who you’re fighting, how can you know what weapon is best?

Members of the Grbic Lab at Western University are working on ways to help commercial greenhouse growers better identify their spider mite enemy, with the hopes it will mean growers will be able to more efficiently and quickly deal with future infestations. They were one of the presenters at last month’s Grower Day, held in St. Catharines.

“We want to catch spider mite before we’re seeing a significant amount of damage,” said research assistant Reagan Sue Michiels.

Vojislava Grbic, a professor in the biology department at Western University, described one situation where a greenhouse operator applied five pesticides that did effectively nothing to the spider mites he had in his facility.

“It was only the sixth that ended up being efficient,” she said.

Part of the problem is that different spider mite species require different pesticides. On top of that, while a few mites may not do much damage, adult females can lay 10 eggs a day.

“It very soon gets out of control,” Grbic said.

So lab members have been working to develop a rapid-result test that growers can do themselves to determine which pesticide to use. It allows them to get a result in as little as three years and within 24 hours in most cases.

“Essentially what we’re trying to do is allow you to make rapid pest management decisions,” said Michiels.

A video of a trial showed the relative simplicity of the test. All growers need to do is get some mites into a vial, wait for the prescribed period of time, and see if they died.

They’ve also been doing plenty of work on spider mite species identification, including an in-lab genetic test that can offer insights into any pesticide resistance that growers may have to contend with in a given infestation.

In recent years new spider mite species have been identified, including Tetranychus turkestani, which currently mostly affects field soybean crops. However, they could be a problem should they find their way into greenhouses.

“It’s clear how devastating they might be in a greenhouse setting,” Grbic said.

Grbic said they’d love to work more with growers to continue developing a better understanding of spider mite populations in Ontario.

At the same time, the Grbic Lab has also teamed up with Greenlight Biosciences to bring a new pest control option to Canadian greenhouse operators. Using RNAi technology, the new tools can perform a similar function as a traditional pesticide, but just one step earlier in the process.

A conventional pesticide uses a chemical to bind to certain proteins the mites need to survive. Without being able to use those proteins the mites then die.

The RNAi process essentially does the same thing, though instead of smothering the protein after its made, it prevents the protein from being made in the first place by targeting the genetic instructions used to produce it.

Grbic said they have high hopes that the RNAi technology will offer growers a new option for pest management, in addition to conventional pesticides and biological controls. 