I received an unusual question from a builder today, and I do not have an answer to his question. Hopefully, you can help me. Here is his question:

"We were involved in the construction of a commercial facility using straw bales. We have since run into a variety of issues with Saw Tooth Grain Beetles that have evidently arrived with the bales and are now setting off smoke detectors. Do you have experience with this ???"

Here is all the information I have found. If you think anything would be helpful, please let me know.

The following information was taken from a website provided by Stuart Bennett and is dated 2003. Thank you, Stuart, for this informative information. Unfortunately, the sawtoothed and merchant grain beetles are fairly prevalent and can contaminate food supplies. The information below is descriptive; however, it speaks to food storage issues, not straw bale houses.

I hope it will be helpful nonetheless in dealing with the infestation. If all else fails, Stuart says, there is always fumigation. Of course, that is something we all want to avoid, I imagine.

It sounds like moisture control, as with bale buildings in general, is paramount with population control. I hope that the food source in the bales is very small and that there is not enough to sustain any new generations.

My concern is that if the beetles are in the home, tripping smoke detectors, they also must have access to your stored food. This would lengthen their life cycle and ability to breed. I think the sooner you can take action against them, the better.

Sawtoothed grain beetles are common stored-food product pests that infest cereals, cornmeal, cornstarch, popcorn, rice, dried fruits, breakfast foods, flour, rolled oats, bran, macaroni, sugar, drugs, spices, herbs, candy, dried meats, chocolate, bread, nuts, crackers, raisins, dried dog and cat food, and other foodstuffs, making them unsalable and unpalatable.

These beetles can chew into unopened paper or cardboard boxes through cellophane, plastic, and foil-wrapped packages. Once inside, populations build up rapidly, often spreading to other stored foods and into food debris accumulating in the cupboard corners, cracks, and crevices. Sometimes, all life stages (egg, larva, pupa, and adult) may be found.

These insects contaminate more food than they consume and usually are discovered, leaving the infested food to crawl about the house. Adults and larvae are external feeders, feeding on finely divided food particles and not whole grains. The insects have running legs (ambulatory), much like cockroaches, and penetrate "tightly sealed" packaging.

Life cycle:

Sawtoothed grain beetles lay eggs singly or in small batches in the food material where the life cycle is completed. The sawtoothed grain beetle cannot fly. Adults usually live about 6 to 10 months, with some living as long as 3 years and 3 months. Female sawtoothed grain beetles usually emerge in April and lay an average of 300 eggs. Egg laying begins about 5 days after emergence and continues up to 3 to 4 weeks. Eggs hatch in about 8 days, larvae mature in 37 days, and pupa about 67 days.

The life cycle of sawtoothed grain beetles can be completed in 51 days or as early as 27 to 35 days, depending on temperature. Merchant grain beetles, which are almost impossible to tell apart from sawtoothed grain beetles by the untrained eye, lay an average of 200 eggs over 28 to 42 days, requiring about 35 days to complete the life cycle. There may be as many as 6 to 7 generations under warm conditions of 85°F to 95°F and 70% relative humidity, with fewer generations throughout the winter months. Adults remain active and feed. The sawtoothed grain beetle prefers cereal-based products, whereas the merchant grain beetle prefers nuts, seeds, and dried fruit.

Damage:

Although broken kernels are the preferred food of both species, sound kernels are sometimes penetrated and fed on. Grain's dry weight may be reduced, but its total weight may increase because of water absorption caused by insect populations' metabolic processes. Molds may begin to grow on the grain, further reducing its quality and value.

Control:

Prevention is the best strategy to avoid insect problems in stored grains. Proper bin sanitation before introducing new grain minimizes the need for pesticides. Good sanitation involves the removal of old grain and dust in and around the grain bin/silo.

This includes the removal of old grain from corners, floors, and walls. Any grain remaining when a bin is emptied can harbor insect infestations, which will move into the new grain. Grain that is to be stored for longer than six months may need a protective application of an approved insecticide.

Grain placed in a clean bin should be checked at two-week intervals during warm months and at one-month intervals during cooler months for the presence of hot spots, moldy areas, and live insects. If any of these conditions exist, the grain should be aerated to lower the moisture level and temperature.

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Happy baling,

-Andrew Morrrison

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