Warehouse Beetles in Organic Storerooms: How can a little beetle be such a problem?

October 27th 2017

by Ashley Roden, Sprague Pest Solutions

A common stored food product pest, Warehouse beetles (Trogoderma variabile) are one of the most destructive of all warehouse pests. While they don’t live inside warehouses, these beetles are strong fliers and are likely living outside the facility at all times.

These scavenger beetles will enter your facility to find nutrition and will eat everything including animal-origin products like wool clothing, other dead insects and animals, and dried milk. They also consume cereal, corn meal, candy, dog food, fishmeal, all kinds of seeds, flour, spaghetti, spices, peas, wheat, and barley. Outside of a facility, the beetles survive on pollen and nectar on plants.

Warehouse beetles are very small – only a little over 1/8 inch (3 mm) in length as adults. They have brown and yellow patterns on their backs. In larval stage, the beetles are tan in color and have numerous stiff setae, or hairs. The setae of the warehouse beetle larvae are shed within the infested food product and can irritate the mouth, throat and stomach of people who eat it. This can cause abdominal pain, vomiting, and diarrhea.

Pheromone traps containing a female sex pheromone are commonly used to attract male beetles. These traps are used both inside and outside the facility. Outdoor traps will help to determine whether the beetles are abundant outside the facility and can be useful to pinpoint when the warehouse beetles become active. Checking indoor traps will alert facility managers when the warehouse beetles have made it inside.

As with many pests, sanitation is key to stopping the Warehouse beetles from reproducing. Start with an in-depth inspection of the facility. Look for not only adults, but also the larva and cast off larval skins.

Examine any cracks and crevices or voids where dust can settle. This includes junction boxes, under conveyer belts, on the tops of beams and pipes, and in drop ceilings – anywhere cleaning does not take place regularly. These beetles can survive even on a thin layer of food powder.

The most common route inside for these beetles is an open door, window or gap. Keeping doors closed as often as possible, and sealing any gaps will reduce the chance of warehouse beetles coming inside the facility. Insect light traps can also be used inside to attract and capture both male and female beetles.

With their diverse food diet, ability to survive outside on nectar and pollen, and their strong ability to fly, do not be surprised if you run into warehouse beetles in your organic warehouse. An integrated pest management program will be vital in solving warehouse beetle infestations.