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Beneficial bugs protect stored grain

Biological control is the use of living organisms to suppress pest populations and reduce the damage they cause.

WESTERN PRODUCER — Intentionally placing bugs in grain and food processing facilities to help manage pests is a tough idea to swallow in Canada, but the practice has been used in Central Europe since the mid-1990s.

Vincent Hervet, an entomologist with Ag Canada in Winnipeg, conducted a literature review on the use of biological controls in stored products including grain, processing facilities and warehouses. He said the practice is already commonplace for many vegetable growers.

“It’s widely used in horticulture, especially in greenhouses. Pretty much all the greenhouses out there use biological control,” he said.

Biological control is the use of living organisms to suppress pest populations and reduce the damage they cause.

“They have issues with aphids, thrips, scale insects and white flies and if they aren’t controlled, they get out of control in the greenhouse,” Hervet said. “So, they need the solution and a lot of people choose biological control solutions.”

Exemptions for beneficial organisms in the U.S. have been carved out by the U.S. Environmental Protection Agency. There are no specific regulations on the use of biocontrol agents in stored products in Canada.

In this country, their use falls under regulations restricting the presence of insects and insect parts in commodities. The 1985 Canada Grain Act prohibits delivering, receiving or trading in infested grain.

However, Hervet argues that in the Act, grain is considered infested if it contains any “injurious, noxious or troublesome insect or animal pest.” Since biological control agents are none of these things, they should be exempt.

Some biological control insects for stored products in North America are already available.

A Quebec company, Anatis Bioprotection, uses a tiny parasitic wasp (about half a millimetre in length) called Trichogramma brassicae Bezdenko. Marketed under the name Tricho-Mites, it is used to control moths in stored product.

The company said Trico-Mites is effective in controlling food moths and clothes moths in homes, museums, businesses and industrial buildings. The product can also be used as a treatment in bulk food stores, grain warehouses and flour mills.

Hervet said stakeholder acceptance, not prohibitive regulations or availability, is the biggest hurdle to adoption of biological controls for stored products.

It took decades for researchers to gradually change the mind of skeptical stakeholders in German-speaking areas of central Europe before they warmed to using bugs to reduce pest issues with stored food products.

“We are talking about introducing insects to places where we don’t want insects, like bakeries and food processing facilities,” Hervet said. “They have a policy of zero insects. So how do you convince them that you’re going to introduce insects?”

“The big part is when you introduce beneficial insects, it reduces the overall number of insects. It has been shown that if you do nothing, you will have many insects. But if you do something, even if you introduce other insects, it will decrease the overall number so it’s still a win.”

He said using biological controls in storage facilities for organic products is a good fit because that industry has few tools to manage infestations.

But even conventional facilities can benefit from biological controls, especially considering that pests are growing resistant to commonly used fumigants.

“The main tool to control stock product pests is fumigation in stored grain,” Hervet said. “The main product used is phosphine and phosphine has pretty much been the only fumigant used for decades now.”

“Pretty much every stock product pest species has developed some resistance to it. So, we need more tools than that.”

There are two types of insects typically used as biological controls. There are predators such as ladybugs that will find their prey and eat them.

“The other type is what we call parasitoids and there are kinds of parasites that will lay one or multiple eggs inside or just outside of the host and when the egg hatches, the little larva will consume that host and kill it,” Hervet said.

“The parasitoid will kill the host and usually very quickly and one advantage it has is that only the larva is a parasite (to the pest). The adult is free living, does not feed on a host. It’s usually a little wasp or little fly. It has wings and feeds on things like nectar, not on a host. So that’s why it’s able to travel great distances to find a new host for its larva.”

He said parasitoids are the most promising for addressing pests that affect grain storage in Canada, largely because they’ve proven effective in Central European facilities.

“There are a number of beetle species that feed on grain and grain products. Also, a number of moths, some mites and others, and they all have natural enemies. If you release these enemies, you can control them (pests),” Hervet said.

“Some of these beneficial insects are generalists like the predators, but some of them are quite specific and usually the parasitoids are fairly specific on a few host species.”

But the utility of biological controls is limited, he said. For instance, if a bin of grain is infested, it’s likely too late to do anything about it because many of the pests will be deep in the grain and inaccessible. It would take too many beneficial bugs to make a meaningful difference.

Instead, there may be a fit where a biological control is used once a bin or facility is empty, to eliminate any lingering pests in the space that would start an infestation when a new batch of grain is added.

“The other aspect of it, which is the one that really works in Central Europe, is biological control in buildings, flour mills, bakeries, storage warehouses, food processing plants and storage facilities. That works a lot better because you have a lot fewer insects to control,” Hervet said.

He is beginning to research which beneficial insects can be used as biological controls for stored products in Canada and is considering only native insect species.

As a grain storage expert, he has recently been contacted by a few companies that are having pest problems.

“I mentioned the potential of introducing a parasitoid for the pest and they were like, ‘Let’s do it,’” Hervet said.

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