Foreign Grain Beetle
09/2022 Issue: (Ahasverus advena) Foreign Grain Beetle
By: John Moore, MSc
A seasonal visitor to Grain Bins and new homes is right on time! The Foreign Grain Beetle is out and about as the fields begin to dry out.
In the U.S., adult beetles of this species fly into stored grain bins, buildings, homes, beginning in late August or early September being attracted by any molds on just about any plant-based materials including wood. The larvae will continue to actively feed on fungi and other fine material. However, these beetles are unlikely to damage stored grain and the population cannot survive if the moisture content of the grain is reduced to less than 13%. Their presence in a bin could indicate that the grain is in poor condition, wet and moldy. This insect is a strong flyer and, from long distances, can easily locate moldy grain in bins and in fields. They can also be present in large numbers in and around new home construction where they feed on the molds that can be present on new drywall, lumber, and other materials where the moisture content is high.
The Foreign Grain Beetle does not damage stored grain. Its presence in a bin is in response to mold growth on the grain or in the bin. The real problem in the grain bin is poor management. When grain is placed in storage and not monitored periodically, moisture can accumulate in the bin and molds then develop. This can occur even if the grain was originally dried below thirteen to fifteen percent moisture. The presence of molds and insects in the grain can result in rejection of sale or reduced market value.
Adults of the foreign grain beetle are attracted to mold, where females deposit their eggs singly or in small clusters. Larvae emerge in four to five days at optimal temperatures (eighty-ninety degrees F). The larvae develop through four to five larval instars in about fifteen days. The adults have an average lifespan of 215 to 250 days. In their natural environment, both the larval and adult stages feed on molds growing on the grain.
Control: Chemical applications to control this beetle are generally not necessary. Infestations are usually self-limiting in that once the material begins to dry and temperature drops, these beetles do not survive. Keeping grain bins dry and clean, keeping moisture content of grains below 15% is usually sufficient in preventing infestations. They are of minor economic importance.