Lesser mealworms, also known as darkling beetles, are associated with poultry litter and manure accumulations. They can cause significant damage by boring into structural materials, and they also serve as a vector for several poultry diseases.

The adults are half-inch long, dark brown to black beetles, and the larvae are light yellow to brown colored and about a half to a quarter inch long. Both adults and larvae live in the poultry litter, where they feed on poultry feed and dried bird droppings.

Moisture from waterers or other sources is necessary for their survival. They are usually found where there is moisture and/or where the litter is looser and deeper. The larvae and adults tend to accumulate under anything lying on or just under the surface of the litter. Floor feeders provide excellent places for them to hide. If nothing is available, they will stay around the edges of caked litter.

Good litter management can greatly reduce numbers of these beetles. Keep the litter as dry as possible, pack down loose litter, and where possible use feeders and waterers that do not sit on the litter but attach to the sides of the coop. Regular complete clean-out and disposal of litter, especially in freezing temperatures that will kill the beetles, is advised.

It is virtually impossible to eliminate these insects from a house with insecticides. They are protected down in the litter and the litter itself may bind the products and reduce their effectiveness. However, diatomaceous earth (DE) may help. The poultry house and litter, nest boxes, and areas where birds take dust baths may all be dusted with DE. Non-heated forms of DE are allowed without restrictions in an organic system. Be sure to use food-grade quality DE - not the DE sold for use in pool and other filters - with crystalline silica content at or below one per cent. DE with crystalline silica content of three per cent or higher is dangerous and should be strictly avoided.

When these methods are insufficient, pyrethrum may be used in an organic production system. Pyrethrum is an effective, though expensive, means of external parasite control. Both pure pyrethrum and pyrethrum/DE combinations are available. Pyrethrum dust may be used in poultry housing and can be applied to the birds themselves.

The annotation in the Organic Materials Review Institute's Generic Materials list specifies that pyrethrum may be used as an external parasiticide. Synthetic pyrethrins and pyrethrum products formulated with piperonyl butoxide are not allowed.

Producers must comply with all label instructions for administration of pyrethrum-based parasiticides to livestock, in addition to complying with the specific regulations pertaining to organic production systems. Producers need to document previous attempts to control parasites using alternative means, such as those described above.

Further Information

• Poultry House Management for Alternative Production by ATTRA
• Pest Management on Poultry Farms by Connecticut Cooperative Extension
• Poultry Pest Management from Alabama Cooperative Extension

December 2013