When you have flour beetles in a warehouse or food facility handling bulk grain, your first job is to determine where the beetles are coming from. They could be breeding in the facility, or they could be brought into the facility in the bulk grain… or both. Here’s how best to sample or monitor different parts of the facility to find the source.
In bulk grain:
The most common detection methods are (1) to take regular samples of incoming material and visually inspect for beetles or their eggs, and/ or (2) take samples and store them in containers to rear out any beetle eggs or larvae in the sample. Grain can be sampled as it is received from a railcar or grain truck, or once it is in storage.
In milling equipment:
Consider inspecting the final sifter after a run to check for insects, insect parts, and eggs. High numbers here but not in the samples of bulk grain suggest that beetles are infesting the equipment itself.
In processed grain/flour:
Manually sift samples of newly ground product looking for flour beetles, parts, and eggs (Which are sticky and tend to accumulate flour dust). The white flour beetle larvae are hard to see in flour. To find them, pour flour dust onto a piece of paper, let it sit for a few minutes, then gently turn the paper over. The larvae often remain attached to the paper.
In the facility overall:
Use aggregation pitfall pheromone traps rather than sticky pheromone traps. Flour beetles are not easily captured on glue traps or sticky board pheromone traps. Once their front tarsi touch the glue, they back away. A pitfall trap captures the beetles in an oily reservoir instead. Place traps low in corners, near doorways, and in critical areas under processing equipment, in storage areas, and in the void space under bin floors.
Flour beetle facts:
Flour beetle adults are active at night and avoid light, just like cockroaches. At night, when lights are turned on, the beetles hide from the light. Although the red flour beetle can fly, beetles crawl slowly from place to place, leaving trails in flour dust. Adult flour beetles can leave a musty odour in the food product and in large numbers, can change its colour. The egg stage is sticky and attracts protective flour dust which makes the eggs very resistant to the physical grinding that takes place during food processing.