Dr. Jacquie Jacob Ph.D., University of Kentucky
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Darkling beetles (Alphitobius diaperinus) are a common problem in poultry facilities. The adults are black with hardened front wings and antennae that start under a ridge near the eyes. The larvae (referred to as lesser mealworms) are worm-like, about 2.5 cm long, and slightly hardened for burrowing. Both the larvae and beetles eat decaying leaves, sticks, grass, dead insects, feces, and grains. They can also feed on dead animals and are known to bite on the skin and drink the blood of turkeys and chickens (Harmon, 2012).
Darkling beetles can carry poultry diseases and internal parasites (Goodwin and Waltman, 1996). The beetles can be a source of infectious laryngotracheitis (Ou et al., 2012), infectious bursal disease (IBD), Newcastle disease, fowl pox, avian influenza, Clostridium, Salmonella (Roche et al., 2009), Campylobacter, and E. coli. Darkling beetles are also secondary hosts for roundworms and tapeworms (Adams, 1998). They also host different turkey diseases such as turkey enterovirus, rotavirus, and coronavirus (Harmon, 2012). They are also known reservoirs of Eimeria, the causative agent of coccidiosis (Goodwin and Waltman, 1996).
The larvae of darkling beetles can tunnel through insulation and wood, reducing their insulation effectiveness (Vaughan et al., 1984). Chickens will eat darkling beetles, but because of their low digestibility, the birds fill up with them rather than their feed—causing a reduction in production performance.
Darkling beetles are native to the tropics and do well in warm humid conditions, such as the inside of a poultry barn. They can be found most often under feed pans and feed lines where spilled feed is mixed with litter. Their life cycle depends on environmental conditions, but is typically 40-100 days. Darkling beetles multiply more quickly as the temperature increases. A single female can live for more than 12 months, laying up to 2,000 eggs over this time (Dunkley, 2010).
Weekly monitoring should be done by looking for beetles in the litter, under feeders, along the edges of caked litter, cracks and crevices, around equipment, under dead birds, and in insulation. It may be necessary to dig 2-3 inches deep in litter every 20-30 feet down the length of the building (Adams, 1998).
Traps can also be used to monitor darkling beetle populations (Adams, 1998). An example of a simple trap is to fill the inside of a 2-inch diameter, 10-12 inch long PVC pipe with rolled corrugated cardboard (same material used for brooder guards). Both the beetles and the larvae will crawl between the cardboard layers to hide. Drill holes at each end so that the pipe can be staked in place. They should be placed in the litter. Avoid the walls, feeders, and waterers since litter is usually tightly packed which discourages beetle infestation. For monitoring purposes, place at least three of these traps, evenly spaced, along the center line of each house.
The traps need to be checked at regular intervals for the numbers to be meaningful. Once a week or once every two weeks should be adequate. Remove the cardboard and count the number of beetles and larvae. If you cannot count the beetles and larvae at the time that the traps are collected, you can place the cardboard into a plastic bag and examine later. The cardboard should immediately be replaced and the trap put back in place. Be sure to record the numbers in a consistent way, e.g., as an average number of beetles per week for each house. While numbers of beetles in the trap cannot be related to numbers per square foot in the house, changes in trap counts over time are what is important.
An integrated pest management (IPM) plan is required (Adams, 1998) for effective darkling beetle control. This would include cultural, biological, and mechanical control as well as the timely use of insecticides.
For dealing with an existing darkling beetle problem, there are organic alternatives to the chemicals used in conventional poultry production. For example, PyGanic Pro® and Evergreen® which are pyrethrum-based insecticides derived from chrysanthemums. Eco-Exempt® is a blend of plant oils used to control a broad spectrum of insects. An additional tool is balEnce™ consisting of a carrier that attracts beetle adults and larvae, bringing them in contact with a species-specific fungus that attacks the beetles. This product is also effective to control other insects including flies, earwigs and hide beetles.
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