Food Companies Beware: Autumn Insects in Peak Migration

With the cooler temperatures, food facilities may experience seasonal pest threats.  We call these pests, fall invaders.  Some of these insects survive the winter through the protection afforded by structures.  They migrate towards buildings in search of a warm resting spot to spend the cold winter. This resting spot may include the wall, ceiling and attic voids of buildings.  Examples of these invaders include cluster flies, boxelder bugs and multicolored Asian lady beetles.  Some fall invaders are attracted to the buildings by light and may arrive more by accident.  These do not spend the winter in the structure but cause concern by their presence in and around food production and storage.  Examples of these invaders include the hairy fungus beetle and foreign grain beetle. 

Who Are the Invaders?

Boxelder Bugs  

Probably the most common of the fall invading insects, this black and red marked bug feeds on trees including the boxelder and maple.  It is ½” long as an adult, mostly black in color with red lines marking the wings and the thorax or area behind the head. 

Brown Marmorated Stink Bug

This insect is relatively new to the United States and has caused major issues on the east coast.  It has also been shipped in commerce to other parts of the country and continues to threaten to move westward.  It is both an agricultural pest and structural pest.  Adults are brown in color, 5/8” in length and a body shape which is shield-like.  They can be identified from similar species of stink bugs by the light bands on the antennae and around the outer margins of the body.

Cluster Fly

There are several flies which will overwinter in structures.  Cluster flies and face flies are the most common and tend to cause the most concern since they often appear in groups or clusters.   The adult cluster fly is slightly larger than a house fly.  The wings are held overlapping each other over the abdomen unlike the house fly, whose wings appear to be more of a triangular pattern when at rest.  It has golden yellow hairs on the thorax or main middle section of the body.  The immature stages are parasitic on earth worms and cause no structural harm.

Multicolored Asian Lady Beetle

These beetles get their name because they can vary in color and markings.  The wing color can vary from tan to reddish orange and they can have a varied number of black spots on the wings.  These insects are predaceous on soft bodied plant pests like aphids, and have a valuable role in reducing agricultural and horticultural pests.  They achieve pest status as they migrate indoors in the late fall months.  They are sometimes called the Halloween beetle because they often come into structures around the time of Halloween on a sunny day after a frost.  These beetles are more attracted to structures with contrasting colors such as light colored siding and dark trim.

Hairy Fungus Beetle

The hairy fungus beetle 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 smaller and more attracted to lights.  You may find these beetles in large numbers in insect light traps.  

Fall Invader Predictions for Fall 2014

Prevention and Control Tips for Food Facilities:

First Line of Defense:  Exclusion

Ideal temperatures for fall invading insects overwintering locations are in the 40-50 F range which is typically found in the exterior wall voids or attic spaces of buildings.  Denying the insects access for these ideal harborage sites is the first line of defense in control.  Use of sealants, door sweeps and screens are the primary exclusion tools in preventing entry.  The table below shows the estimated time frames for the fall invading insects to move into and out of structures. This table can be used to help plan proper sealing times. It is best to seal after insects leave the building and before re-entry in the fall or late summer.  Indoor migration timetables will vary based on geographical location.

Fall Invader Timetable

Reduce Attraction

Since some of these insects, like the foreign grain beetle, can be attracted to structures by light, light management is considered an important step.  Mercury vapor lights are more attractive to insects than sodium vapor lights.   For this reason, low pressure sodium vapor lights are preferred.  Newer, LED lights can offer another option.  Be sure to select LED lights with the spectrum similar to the low pressure sodium lights.  If mercury vapor lights are used, it should be as part of a push pull strategy.  Place these lights around the property perimeter to pull insects away from the building.  Use the high pressure sodium vapor lights closer to the building.

Many of the fall invaders will be attracted to areas of the building where there are contrasting colors.  So the juncture where a dark brown window frame meets a pale brick building will be attractive.  Although it may be impractical to paint or change the building color, this knowledge can be useful in making sure that these areas of contrast are effectively sealed.

Insecticidal Control

Perimeter treatments around the exterior of food facilities with insecticides can be used to supplement exclusion efforts.  The applications should be made to areas where the insects are resting and entering the plant.  Timing of the applications can be critical to achieving good control.  

Physical Removal

If the timetable for exclusion and preventative pesticide treatment was not met and the insects make their way unrestricted, insect light traps may be helpful in attracting and eliminating some of the insects which are not confined in ceiling or wall void spaces.   Occasionally,  a number of the invading insects will wind up in the occupied spaces of the building due to their point of entry or they may emerge in winter due to a temporary “January thaw” situation in belief that it is spring time.  Smaller portable, battery operated light traps can be useful in small areas for attracting insects and may offer some relief.

In addition to light traps, insects can also physically be removed through the use of vacuums.  If vacuums are used, the contents should be discarded right after vacuuming has been completed.  Some of the fall invaders can release foul odors and prolonging their time in the vacuum can taint the vacuum.

Patricia Hottel is technical director at McCloud Services, based in South Elgin, Ill.  McCloud Services serves the largest food-related brands in the U.S.  For more information, please visit www.mccloudservices.com.