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COUNTRY LIFE IN BC • FEBRUARY 2017


Knockout punch eludes researchers in wireworm battle New chemistries are low risk, low impact


by TOM WALKER


AGASSIZ – Bob Vernon has a difficult task.


A research scientist with Agriculture and Agri-food Canada, his job is to find solutions to control wireworm populations and the damage they cause. While he’s found a way to protect potatoes, he continues to seek effective methods to manage these pests in other crops in BC and across Canada.


“I approach this work with the needs of the farmers in mind,” says Vernon from his office at the Agassiz Research and Development Centre. “It is frustrating when I can’t come up with the controls that will completely solve the wireworm problem before farmers start losing their yields and investments.”


Populations of wireworm, the larvae of click beetles, are growing worldwide. Vernon and his colleagues believe that as the residues from the old broad spectrum


organochlorines (OC) such as DDT (a class of chemicals no longer in use) dissipated from soils, wireworms found a chance to re-establish themselves.


“BC potato growers started


to see damage in the early 1990s,” says Vernon. “We think the OC residues had gone low enough that, when the adult click beetles coming from undisturbed grassy border areas laid their eggs in rotational fields of cereals or grasses, they started to survive.”


Click beetles emerge from soil in the spring and this is the time they can spread. Eggs are laid in late spring and hatch through the summer. The larvae move down through the soil to escape summer’s heat and move up to feed in the fall. That’s one of the first problems: wireworms change soil depths – now you see them, now you don’t. Secondly, they have lots of cousins. There are at least four species of economic concern in BC.


“Sometimes, more than one species can be in a field at once,” says Vernon, adding there are some 20 species of concern across Canada. “A treatment that works for one species may not work for another.”


Second, they really hang around. BC wireworms typically live four years in the soil before pupating in late


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summer, changing to adults in the fall to overwinter and emerging again in the spring. Wireworms


have two feeding cycles. A potato farmer can protect mother seed in the spring only to find wireworms munching the daughter tubers in the fall. The


Risk reduction


A third problem is the rise of risk reduction programs


that have removed chemical treatments


BOB VERNON


feeding leaves blemishes that make the crop unsaleable.


formerly effective in killing wireworms. Thimet, for example, was linked to raptor deaths in BC in the 1990s and its loss wasn’t necessarily a bad thing in the big picture. However, it’s


forced Vernon to find alternative chemistries that are equally effective.


Two candidates are Titan, a neonicotinoid employed as a seed treatment, and


Chlorpyrifos, used as an in-furrow spray


“Growers are getting much the same protection as they did with Thimet,” says Vernon. However, both insecticides are under review and the search continues to find new low-risk alternatives.


Moreover, few of the new, low-risk chemistries kill wireworms.


Vernon’s lab has found that the new generation of insecticides render the wireworms unconscious (neonicotinoids) or repel them (pyrethroids). Crops might be protected, but wireworm populations remain untouched.


Wireworm victory needs more than a silver bullet


by TOM WALKER


AGASSIZ – Agriculture and Agri-food Canada scientist Bob Vernon knows pesticides aren’t the only weapon growers have in their battle against bugs.


Researching new


chemistries to fight wireworm is important, but Vernon is also investigating effective treatments for adult click beetles as they emerge from fields or borderlands in the spring.


Vernon has invented the “Vernon pitfall trap” which can help detect the presence of a key pest species or trap males en masse. A single trap caught 22,000 male beetles in PEI last year, for example.


“We are looking to see if we can gobble up all the males


before they can mate,” says Vernon. “Then, the eggs that are laid will be sterile and that will help reduce populations.” Todd Kabaluk, Vernon’s colleague at the Agassiz Research and Development Centre, hopes the fungus Metarhizium anisopliae, which kills click beetles but leaves beneficial insects unharmed, could help. In Charlottetown, federal scientist Christine Noronha has worked with PEI growers to study the impact of green manures of brown mustard or buckwheat. “We are not sure how it works,” says Vernon. He says click beetles don’t like brown mustard or buckwheat, potentially reducing egg deposits in fields where they grow.


The natural chemicals given


off when the greens are ploughed under may also kill newly hatched wireworms. Working the soil may also move young wireworms away from food sources, starving them. When the cover crop is turned under in late summer, it may crush the vulnerable pupae.


Throughout his work, Vernon has carefully perfected a sure-fire strategy that kills wireworms with low doses of chemical. He just doesn’t have a registered chemical he can insert into the strategy – yet. “I came up with the idea of attract-and-kill about 10 years ago,” he says.


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At potato planting, wheat seed treated with small amounts of insecticide can be companion-planted in furrows. Since wheat germinates faster than potatoes, the wireworms are attracted to the seed by the carbon dioxide it gives off. They contact the seeds and die, leaving the potatoes untouched.


“We have got a 90%


reduction in wireworms using one to two grams of active Fipronil per hectare,” says Vernon. “Compare that to 3,250 grams per acre of the old Thimet.”


But Fipronil, which is


1-877-849-9049 www.wecover.net


registered in 70 countries, isn’t available in Canada. Still, Vernon is hopeful. “Our lab is considered one of the best in the world doing this work and companies are at the door asking us to test new chemistries all the time,” he says.


He just has to find that ‘silver bullet’ and load it into his attract-and-kill strategy.


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