Cold weather a blessing for storage insect problems

By Tim Kalinowski, Staff Writer

With the onset of colder temperatures in much of Alberta and Saskatchewan the past few weeks, Paul Fields, a research scientist with Agriculture and Agri-Food Canada, says it is the perfect prescription for those with insect infestations in their grain storage bins.

“We are blessed with the cold weather,” says Fields. “I say that and people laugh, but cold weather allows us to cure a lot of problems.”

Fields says the two most common types of insects found in prairie grain bins are the Rusty Grain Beetle and the Red Flour Beetle. There is a reason for this: These two species are by far the most cold acclimated of the various insect pests found in storage. Thankfully, Canadian farmers are often spared from the even more destructive species found south of the border where warmer temperatures prevail.

“Every year we have problems with these insects,” confirms Fields. “They are often difficult to detect. They come in at harvest when the grain is warm and both of these insects multiply quite rapidly. They can increase sixty fold per month under ideal conditions. Both of these insects need to have a bit of a break in the kernel. About 20 per cent of the kernels have enough of a break for them to imbed their way in and feed on them. They are solely storage insects and not found in the field. They can feed off a variety of things; they can even feed off mold found in the grain. They do fly and can fly around and infest other grain in the area.”

The best thing a farmer can do to prevent these two critters from getting a hold in his bins is not to let them establish themselves in the first place.

“Grain is a great insulator,” explains Fields. “So if you don’t have an effective aeration system, although it can be minus 15 C outside, in the grain it can be plus 15 or 20 degrees in the centre of that bin. The best thing to do once the grain is in there is take off the harvest heat. You aerate and take the grain’s core temperature down to below 18 C when you first put it in. At 18 C these insects won’t develop because the temperature will drop exponentially as it continues to cool. You might have in a few in there, but they won’t multiply.”

If prevention is not possible, Fields says cold winter temperatures, proper aeration and a little patience can be the great equalizers without need for more expensive chemical treatments.

“If you get the core of the temperature (inside the bin) down to minus 5 C that takes 12 weeks to kill all the insects. Minus 10 C it takes eight weeks. Minus 15 C it takes four weeks. And minus 20 C it takes one week. And you can then be sure that grain mass will be free from insects.”

The good news, according to Fields, is that this prescription for killing the Rusty Grain Beetle will take out all other varieties of storage based insects as well.

“We do occasionally get other insects that are more common down in the United States like the Rice Weevil, the Lesser Grain Bore and the Granary Weevil,” explains Fields. “All these insects are sometimes found in Canadian grain, and all these insects are more destructive than the Rusty Grain Beetle because they can attack solid kernels and turn those kernels into husks. But the method of eradication is the same. The Rusty Grain Beetle is quite cold tolerant. So if you use the temperature control I have already described, and aim for the Rusty Grain Beetle, you will definitely get these other insects also.”

Those with an insect problem in a hurry to find a cure can use various insecticide options. Fields says the most common type of fumigant used is Aluminum Phosphide which dissolves in the moisture inside the grain bin to create Phosphine gas.

“Aluminum Phosphide is a fumigant that needs a licensed fumigator to use. These are small pellets that you put into the grain and that reacts with the moisture in the air in a way which dissolves and produces the gas. It doesn’t work at low temperatures, however. The minimum grain temperature you can use it at is at 5 C. Also the lower the temperature when you apply the Aluminum Phosphide, the longer the time you have to maintain the gas.”

There are more expensive brands that do work at lower temperatures, but Fields says if you are not in a hurry you are better off using the cold weather to deal with your insect problem. He also says it is important to know what critter you are dealing with before deciding to take extra steps like insecticide treatment. To this end, he and several of his colleagues have developed an iPhone app called “Insects in Stored Grain” which producers can download. The question and answer format and high quality photos allow instant access to information on the most common types of storage insects found in Canada. There is also a desktop version available on the Canadian Grain Commission website.

“They are all little brown bugs,” says Fields with a laugh, “but it really does matter what little brown insects you have.”