Controlling disease-carrying darkling beetles in poultry
By Mike Catangui, Ph. D
Biosecurity aims to protect poultry from diseases
Darkling beetles (other names: litter beetles, black beetles, lesser mealworms; scientific name: Alphitobius diaperinus) [Figs. 1-2] are an important insect pest of poultry (mainly in broilers and turkeys) in the United States. They can directly injure chickens and cause undesirable skin blemishes that can result in dockage at harvest [Fig. 3], damage poultry housing structures [Fig. 4], and carry disease-causing microorganisms.
Disease-causing microorganisms that can be vectored by darkling beetles are E. coli, Salmonella, turkey coronavirus, Marek’s disease virus, Newcastle disease virus, coccidiosis protozoa, and poultry tapeworms, among others.1 Table 1 lists important diseases that can be spread by darkling beetles in poultry barns.
Benzoquinones emitted by darkling beetles to defend themselves from predators can cause allergic responses in sensitive farm workers.2,3 Other detrimental effects of darkling beetles in poultry include intestinal obstruction in young chickens and turkeys, reduced average daily weight gains, and feed contamination.
Biology of darkling beetles
Darkling beetles or lesser mealworms are mainly pests of stored grains and seeds (wheat, barley, rice, soybean, cowpea, linseed, cottonseed, and peanuts) and processed products (flour, oatmeal, tobacco, and dried meat).1 The grain-based feed, plant based beddings (rice hulls, oat hulls, peanut hulls, wood shavings, sunflower hulls, and cotton plant residues) and low lighting conditions may all contribute to the abundance of darkling beetles inside broiler and turkey houses in the U.S. Both the larval and adult darkling beetles have chewing mouthparts used to chew on food, and also for biting into the skin of chickens (and sometimes humans), and burrowing into building foam insulations [Fig. 4], wood, and soil [Fig. 5].
Knowing in advance which insecticides are efficacious will lead to a more successful, economical, and environmentally-responsible darkling beetle integrated pest management program (IPM).
Darkling beetles undergo complete metamorphosis and go through the egg, larva, pupa, and adult stages [Figs. 1-2]. On average, darkling beetles can complete their development from eggs to adult beetles in about a month (36 days) at 86°F to as long as 164 days at a lower temperature of 68°F. No egg hatch and larval development are known to occur at 62.6°F or lower,4 but darkling beetles can avoid temperature extremes by digging into the soil [Fig. 5]. Adult female darkling beetles can live for more than 2 years and lay more than 2,600 eggs in a lifetime at room temperature.5
Controlling darkling beetles for biosecurity
Darkling beetles can be controlled effectively by synthetic and organic insecticides that fall into two categories. Empty-barn residual insecticides [Table 2] can only be applied between flocks when the chickens or turkeys are not in the poultry house. Application of these insecticides can be made using an ordinary backpack pump sprayer or a spray system mounted on a truck or an all-terrain vehicle.
The birds can be placed into the treated house as soon as the residual spray droplets have dried out. Solid formulations such as Zone Defense® and ZetaGard® LBT can be applied using a drop spreader. Empty-barn residual insecticides are long-lasting and are expected to control darkling beetles through the duration of the flock, which can be between two months (broilers) to four months (turkeys). As the name implies, empty-barn insecticides cannot be applied or drifted onto live poultry. Most empty-barn residual insecticides are effective against both darkling beetle adults and larvae; some like Tekko™ 10 and NyGuard® IGR Concentrate only work on the larvae [Table 2].
On-animal insecticides [Table 3] are insecticides that can be used, if necessary, to control darkling beetles while live birds are present in the barn (within-flock insecticide treatment). These insecticides are designed to quickly kill darkling beetles without leaving persistent residues on the animals and the poultry house. Most on-animal insecticides are of natural origins such as natural pyrethrins and spinosad. EverGreen® Pyrethrum Concentrate may be used in organic poultry production.
MWI offers insecticide resistance testing
MWI Animal Health offers the testing of darkling beetles for resistance to insecticides. Because darkling beetles are known to develop resistance to insecticides quickly, we recommend regular testing of local darkling beetle populations for their susceptibility to all active ingredients that are being considered for darkling beetle control. Reduced efficacy of any insecticide over time may indicate development of resistance by the target darkling beetle population. Knowing in advance which insecticides are efficacious will lead to a more successful, economical, and environmentally-responsible darkling beetle integrated pest management program (IPM). Make sure to consult with your MWI Animal Health territory manager about our darkling beetle insecticide resistance testing program and the procedures for submitting darkling beetle samples for testing.