The primary problem with secondary pests


May 3, 2021

Indianmeal moth Photo courtesy of, and copyrighted by, Gene White,

Indianmeal moth (Plodia interpunctella). Photo courtesy of, and copyrighted by, Gene White,

Stored product pests (SPPs) don’t just damage food products, they can also destroy your clients’ reputation and profits — not to mention your relationships with them. In fact, the Food and Agriculture Organization of the United Nations (FAO) estimates that invasive insects cost the U.S. $70 billion annually. It’s no wonder, then, that food-handling facilities are quick to act and slow to have patience when SPP are involved.

To mitigate product recalls, returned shipments and facility infestations, many food handlers jump to worst-case scenario reactions and call for drastic measures. These include plant shutdowns, which cost them thousands of dollars, and even more money in lost production time. This is where pest management professionals (PMPs) need to step in and ask food handlers to take a moment and trust the expert PMPs, because drastic measures aren’t always necessary.

The reason is simple. What some PMPs may forget is that pests that are attracted to stored product are broadly sectioned into two groups: primary and secondary SPP. That may not seem like an important distinction, but it can be the difference between a labor-intensive, large-scale fumigation or simply asking the clients to restack product on synthetic pallets.

Here is why: Primary SPP infest healthy, whole grains directly, while secondary SPP feed on broken kernels, grain dusts and molds that grow on or near the product. For example, insects feeding on mold that can grow on wooden pallets can be the culprit. Once the mold is gone, so is the insect.

While a primary SPP infestation does indicate activity in the grain product, a secondary SPP might only be feeding around the food product. This is especially challenging, since secondary SPP can look much like primary SPP to an untrained eye. But by doing some homework, PMPs can save clients a lot of time, money and frustration.


The first step in managing pests is to identify what is found. Make sure a clear image of the pest or an intact sample is gathered, and take the time to get proper identification. From there, the biology of that insect and a detailed inspection will inform a plan of action that may or may not involve the application of pesticides.

Never forget the basics when it comes to pest management!

BLAHNIK is field training manager for Milwaukee, Wis.-based Wil-Kil Pest Control and Holder’s Pest Solutions. He may be reached at


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