Springtails on glue boards

Pests Associated With Moisture and Mildew

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Pests Associated With Moisture and Mildew

by Jody Green, Extension Educator

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The pests in this article are considered nuisance pests. They may be found inside in large numbers, but are not of concern to human health or structural integrity, as they do not bite, or feed on blood or building material. Their presence is an indicator there is high moisture and conditions conducive to mold or mildew. .


Springtails are small (approximately 1/8" to 1/16" long - shown on the glueboards in the photo above), slender, soft-bodied insects. They are wingless and do not fly, but sometimes jump. Springtails have a forked appendage, called a furcula, which remains unseen and tucked under their body until it needs to propel itself through its environment.

Springtails occur in areas of high moisture. They come in many shapes and sizes. In nature, they are considered beneficial since they are decomposers and help breakdown organic matter to recycle nutrients back into the soil.

Springtails can be found in any type of environment, but get the attention of homeowners when moisture is high and when present, springtails can be found in the thousands. They are often found on floors, around windows, in basements, crawl spaces, bathrooms and kitchens. Look for plumbing leaks, roof leaks, entrance from outdoor foundation, areas of condensation around appliances, damp floor mats, overwatered houseplants, and fabrics not fully dried in the dryer and left to fester.

If there is sufficient moisture around the structure, outdoor sanitation and maintenance may help decrease the moisture indoors that support high numbers of springtails. Some recommendations would include checking the grade, cleaning the gutters, diverting the downspouts, adjusting the sprinkler heads and removing vegetation or mulch from close to the foundation.

Interior management strategies include removing them by hand, trapping on sticky glue boards and vacuuming them up. The use of insecticide spray indoors is not recommended as it has not been shown to be effective.


Psocids (pronounced So-sidz) are approximately 1/16" in length, light gray to brown in color with long slender antennae. Psocids can be identified by their large, visible nose called a clypeus.

Psocids are mildew-feeding insects that feed on a variety of starchy plant and animal material. They can be found infesting stored items in locations with poor ventilation, such as attics, cellars and other non-air-conditioned storage rooms.

Their survival depends on high humidity and are often found feeding on mildew growing on pages of books, newsprint, wallpaper, furniture, dried fruit, grains and other damp items.

The best way to control psocids indoors is to eliminate the damp conditions that support the molds on which they feed. Lowering the relative humidity to less than 50% will prevent psocid development. This can be done by utilizing air-tight storage containers for food products and paper mementos, providing better ventilation, increasing air circulation and using a dehumidifier.

Foreign Grain Beetle

Foreign grain beetles are tiny reddish-brown beetles approximately 1/16" long. When viewed with a magnifying lens or microscope, they have small projections behind the head and an enlarged 3-segmented club at the end of the antennae. They have a pair of hard wing covers that hide a second pair of membranous wings underneath. They are strong fliers and can accumulate on the walls and ceiling in the hundreds.

Foreign grain beetles feed on molds and mildews which can be found growing on damp grain. They become pests inside newly constructed houses and buildings — particularly in the fall — when excessive moisture is trapped in the wall voids and create an environment conducive to the growth of molds and mildews on wood and drywall. Under optimal conditions, when humidity is above 65%, they can complete their life cycle in 30 days. Because the beetle is highly dependent on humidity, numbers will drop when humidity falls below 60% and beetle population will subside. Within the first year, new houses will dry out and lose a great proportion of their water. Modifying the environment can help accelerate the process by increasing air exchange inside the building by adding fans and vents, or perhaps running a dehumidifier.

If you experience a high number of mildew-feeding beetles but your house is not of new construction, their presence could indicate a water leak or moisture problem in the home. Further investigation is recommended, but insecticide is not.

There are a number of other small beetles besides foreign grain beetle that feed on microscopic mold.

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Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the University of Nebraska–Lincoln is implied. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office

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