BANFF, Alta. – When it comes to snaring a male wheat midge, all it takes is some female chemistry.
A team of scientists led by Simon Fraser University researcher Gerhard Gries is in the early stages of using natural chemical sexual attractants called pheromones to slow down the damaging pest.
Orange wheat blossom midge has been a problem in Manitoba and Saskatchewan for years and is now becoming an expensive nuisance in Alberta. Saskatchewan farmers alone suffered $70 million in production losses in 1997.
Gries told a cereal pest management seminar in Banff that there is a two-pronged approach to the pheromone research.
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One is to use it in traps to help farmers identify economic thresholds for traditional insecticide spraying.
The other is to use pheromone spraying instead of insecticides.
Small studies have already showed promising results and he hopes to expand to field level testing if funding is approved.
The researchers used the pheromone-baited traps to get an accurate count of pests in the field, which helped them identify economic thresholds for spraying.
The traps are considered more efficient than counting insects on wheat heads, one of the existing tests for infestation.
“Current methods are not very sophisticated or appreciated by farmers,” Gries said.
It is also possible to reduce infestation levels by drawing males into traps, where they die. On the wider front, Gries thinks pheromones can also help replace insecticide spraying.
“We think very little pheromone should be needed for wheat midge mating disruptions,” he said.
This is because the female naturally emits tiny amounts of the pheromone to attract a mate. By disrupting mating, farmers would reduce egg laying and therefore larval numbers. This is important to cutting midge damage because crop damage occurs during the larval stage.
After hatching, the midge larva feeds on the developing wheat kernel, causing it to shrivel, crack and become deformed.
While limited trials show the pheromone traps were effective, large scale mating disruption requires a suitable commercial application method. Farmers need to be able to spray it on fields using normal field equipment.
Scientists have already found a way to encapsulate the pheromone, which would then be released over a field. It needs to last for several weeks while the insects are flying. Males are attracted by the scent in the field and become disoriented. They cannot find the females and do not breed.
The pheromone must also be effective as the insecticide Lorsban, which is what farmers now use to control wheat midge. Lorsban costs $13 per acre.
At 67 cents per gram per acre and with an application rate of 19.4 grams per acre, which also works out to $13 per acre, Gries estimates the pheromone will be competitive with Lorsban.
“We like to think we will need less pheromone to achieve our objective,” he said.
It is hoped if the federal government approves this natural chemistry, it could replace organophosphate insecticides now in use.
Organophosphates are controversial. In the United States, the Environmental Protection Agency is reviewing the chemicals because of their widespread use and opportunities for human exposure. Also, they are nonselective and kill valuable parasites that attack pests.
