Stored product pests a challenge for pest managers

01/06/2021

Dealing with stored products pests can be a real challenge for pest managers, especially when it comes to identification and treatment recommendations. Although considered 'minor' pests, a wide range of insects fall within the category. Many small species of Coleoptera beetles and Lepidoptera moths attack and destroy foodstuffs, with a few common pests being the grain weevil, lesser rice weevil, grain borer, rust-red grain beetle and warehouse moth. These insects exploit stored products as a food source or a habitat and pose a risk of spoiling food supplies in both people’s homes and food processing plants.

They cause economic loss through damage and contamination, making foodstuffs unfit for human consumption, destroying items such as grain, cereal, fruit, nuts and seeds. Most stored product pests are tropical or sub-tropical in origin, preferring warm, relatively humid conditions. It’s been estimated that one third of the world grain crop is lost each year during storage, much of it due to insect attack. 

Stored product pests are troublesome at all points of food handling including warehousing, transporting, distribution, and in restaurants. Establishments that handle food materials should carry out regular inspections to limit the number of pest outbreaks. These pests also find their way into people’s homes, with pest managers being asked to identify and treat the problem in people’s pantries. Often the first indication is small moths flying around or beetles in or around food packages.  

A pest manager’s initial inspection is essential to determine the extent of the infestation, whether it be at a commercial or residential premises. This means carefully examining all potential sources of infestation – not only the pantry and kitchen for any insect activity in food packaging but looking in cracks and crevices where insects may be breeding in accumulated food debris. Don’t forget to check for old rat baits in the ceiling and subfloor area – having a high grain content, they are a common food source for stored product pests.

When it comes to identification, the adult moths (Lepidoptera) and adult beetles (Coleoptera) are easy to distinguish from one another, but their similar-looking larvae are a little more difficult to identify. Use a hand lens to examine the legs of the larvae: beetle larvae are grub-like and legless or have three pairs of legs all located close to the head; moth larvae have three pairs of true legs and additional leg-like structures farther down the abdomen. 

It is worth noting that both larvae and adult beetles feed on foodstuffs, but it is only the larval stage of moths that cause damage to stored products. 

Treatment requires an integrated approach of sanitation and hygiene with a judicious use of insecticides. Most often, by the time we are contacted to deal with these pests the infestation has already spread. The source is commonly packaging that is damaged, unopened or forgotten. If you find beetles crawling or moths flying around, the best thing to do is seal the packaging and mechanically remove the infested product and destroy it immediately.

Following removal, use surface sprays to control wandering adults that may start a new infestation. After the treatment is completed, make use of monitoring glue traps to assist with the detection of any new infestations.

Bruce Gow from A1 Pest Control was recently contacted by one of his customers who was having an issue with moths in his pantry. The customer wanted him to come out and identify them and perform a treatment. I recommended for Bruce to try Bayer’s newest general insecticide Suspend Flexx, which has a broad spectrum of activity, flexible application rates, is cost-effective and labelled for use against stored product pests. 

Mr Gow said, “Ever since I started my first pest control business 38 years ago, we’ve always used Bayer products because they had a solid reputation for effectiveness, safety and customer support. I recently used Suspend Flexx on a job to treat pantry moths. We wanted to use a product that was safe, non-fuming and that wouldn’t stain surfaces. 

“Once we made the decision to use Suspend Flexx, we found that it was very effective when combined with a very thorough inspection and physical control methods. The results were immediate, with zero callbacks after a few weeks of the service. These great results were gained with a very low cost of application.”  

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