Invasion of the Mold Feeding Beetles

Fall brings cooler temperatures and with the changes in weather, plant managers may see an increase in pests moving into structures.  Some of these invading insects may be tied to moisture and mold that can be found in farm fields, silos and grain and grain product storage areas.  Included in this group of mold feeding insects is the foreign grain beetle, hairy fungus beetle and the minute brown scavenger beetles.  Some of these beetles are extremely small and may enter through normal screening.

The food industry needs to take precaution of the below Mold Feeding Beetles this fall:

  •  Minute Brown Scavenger Beetles

This is a group of beetles ranging in size from 1/32” – 1/8”.  They are typically brown to reddish brown in color.  The front half of the body (head and thorax) is narrower than the rear of the body (abdomen and wings).  There are groves in the wings which cover the abdomen.  Both the immature stages and adults feed on mold spores and will be found in areas where there is fungal growth including grain in poor condition.

  •  Hairy Fungus Beetle

The hairy fungus beetle is a group of beetles which may come in from the outside.  It is associated with mold and is light attracted.  One common species we find in food plants can be confused with the cigarette beetle due to its size, color and shape.  It is oval in shape with a three clubbed antennae.  The antennae of the cigarette beetle are saw-like in shape and not clubbed.

  •  Foreign Grain Beetle

The foreign grain beetle is a common late summer and fall invader.  It feeds on grains in poor condition and the fungus associated with the deteriorating grain.  They are 1/16”- 1/8” in size.  They look similar to flour beetles in color and body shape but are typically smaller and more highly attracted to lights.  You may find these beetles in large numbers in insect light traps.  They are reddish brown in color and have a three clubbed antennae.  To confirm that they are foreign grain beetle and not a flour beetle, look at the area behind the head.  There are two lobes at the top corners of the thorax.  You will not see these lobes on flour beetles.

Prevention tips include:


All of these insects are light attracted and will be attracted to the lighting around buildings.   Mercury vapor lights can be 112 times more attractive than sodium vapor lights and should not be used on structures when possible.  In addition, as with any exterior invading insect, exclusion is important.  Food facilities should do the following to prevent entry of these beetles into their buildings:

  •  Make sure doors and windows are kept closed or use tight fitting screens
  • Screen vents or other openings which may provide access
  • Seal openings in exterior walls around pipe/wall junctures which might provide pest access
  • Use sodium vapor or LED lights in the range of 575-600 nm for lights mounted on the structure
  • Consider use of motion sensor lighting when appropriate to cut light emissions
  • Keep grain and food spillage around the structure to a minimum
  • Use the more attractive mercury vapor lighting at the property perimeter
  • Check incoming goods to make sure that beetles are not introduced on shipments