Insect Identification and Information - Warehouse Beetle

08/2021 Issue: Outside pressure from Warehouse Beetle could present some risk.

This time of year, the  exterior population densities of Warehouse Beetle (Trogoderma variabile) can be extreme resulting in sudden increased capture numbers in pheromone monitoring system you may have in place on the interior of your facility. These extreme population densities seem to be very regionally biased with little numbers in the east and very high numbers in the Midwest and upper Midwest.  This regional difference can be based upon differences in temperature, rainfall, food availability, and overall population that successfully over wintered which can change regionally year after year.

With large numbers of these beetles on the exterior of the facility, it is inevitable that some will find their way to the interior.  This can be concerning as this stored product pest is medically significant causing illness in some people and pets if larval caste skins are ingested.  Therefore, food safety risk is elevated if the beetles that do wander in find appropriate resources to establish an interior reproducing population.  Here are some things that you can do to help mitigate this increasing risk:

  1.  Sanitation, Sanitation, and more Sanitation.  Food spillage in difficult to clean areas such as racking supports, processing equipment, etc.  unfortunately, those areas that are difficult to clean or maintain in a cleanly state are what the Warehouse Beetle loves.  Grain based products,  dry proteins (pet food is a favorite) and other product dust and cast off. 
  2. Make sure door policy is enforced.  No doors left open at any time unless actively engaged in loading or unloading. 
  3. Make sure all windows, vents, or other building penetrations are tightly sealed or have appropriate insect screening.
  4. Make sure building has positive air pressure if possible.  These makes it difficult for the beetles to fly in.
  5. An exterior application of an appropriately labeled residual pesticide on vertical surfaces around entry points can reduce the numbers of these beetles entering the facility.  Do this in early June, July, and August
  6. Insect light traps when correctly placed on the interior do a good job of intercepting many of these beetles.
  7. Consider using pheromone monitors on the exterior as an early warning system.  You will identify population pressure surges sooner.

Adults are strong flyers and can move throughout the facility in a single day.

Adults are oval and 2.0 to 4.6 mm in length with females being larger than males. 

Elytra are generally dark with different colored contrasting bands that vary from brown to red.

Adults are generally dark brown with 3 lighter brown or reddish bands.

Larvae are whitish yellow initially and darken with age.

Foods:  Warehouse beetles are voracious feeders. They have been reported from seeds of all kinds, dead insects and animals, cereal products, candy cocoa, corn, corn meal, dog food (dried and ‘burgers’), fishmeal, flour, oatmeal, milk powder, spaghetti, spices, peas, wheat, barley, and pollen.