Guardian Pest Solutions with Hao Yu


March 1, 2013

Headshot: Hao Yu Stored product pests are a common problem for Hao Yu, technical director at Guardian Pest Solutions, which is based in Duluth, Minn. He shares his wisdom and experience with Pest Management Professional (PMP).

Q: What’s the largest stored product pest infestation you’ve seen, and how did you battle it?

Yu: We have a food manufacturing company that had an Indianmeal moth (IMM) problem for a while. It happened in the storage and production areas and, because it was getting worse, in the final product. It was a massive job because the company had a huge warehouse where raw materials were mixed with the final product, which isn’t a best practice. We identified the problem, spent a lot of time inspecting for it and worked with the manufacturing client to solve it.

The first thing we recommended was training the shipping and receiving person. If he sees something obvious, he picks the materials out and puts them in a separate quarantine area. Anything coming from a suspected source or highly susceptible area should be put in the quarantine zone until it’s all cleared or inspected for IMM or other stored product pest activity. Then they can be brought into the storage area.

In the warehouse and the storage area, we used mating disrupters, which are pheromone traps that confuse the males so they aren’t finding the females. This stops the breeding cycle. Also, we looked for a source throughout the warehouse. We stayed on top of inspecting and monitoring the situation. We also talked to the client so it could do a better job storing product and separating the raw materials from
the finished product.

Q: What’s the most difficult stored product pest infestation you’ve encountered?

Yu: IMM are difficult to find because they tend to stay in containers. Unless you search every bag, you have to wait until you see the moths and know there’s a problem. By that time, the product is in bad shape.

Also, the saw-toothed grain beetle, which is the smallest beetle in the stored product pest category, can penetrate packaging easily. We’ve run into several places where we found the beetles, but we didn’t know where they were coming from. We have to come in overnight and spend a lot of time flipping through every bag to narrow it down.

Most of these treatments are organic related because we follow integrated pest management (IPM) steps as much as possible. IMM are flyers, so the pheromone traps work pretty well, and you can narrow it down to a certain area. For beetles, if they don’t fly, you can set up monitors on the floor, pallets or shelving to see where they’re coming from.

Hao Yu’s  Dos & Don’ts

■ ID the pest you’re dealing
with correctly.
■ Inspect thoroughly. If you find the source, you’re 90 percent there with stored product pests.
■ Use pheromone traps in high-risk areas, and stay on top of changing the lures when necessary.

■ Underestimate how much time you’re going to spend on each job.
■ Don’t rely on the client to finish the job you want them to do, such as cleaning up or sealing holes. Remind them, or offer your services.
■ Take it too easy and overlook signs. Stored product pests can be difficult to find and eliminate.

Yetzer Simon can be reached at

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