Canadian Poultry Magazine

Features Manure Management Production
Darkling Beetle Control

Control measures need to practised regularly to prevent economic losses and structural damage

A true survivor and almost impossible to completely eradicate, the
darkling beetle can eat away at profits and affect bird health and
performance when left unchecked in a poultry barn.

A true survivor and almost impossible to completely eradicate, the darkling beetle can eat away at profits and affect bird health and performance when left unchecked in a poultry barn.

A significant pest
Darkling beetles can have a huge economic
impact on a poultry operation. Chicks adore them as feed (above is an
example of a chick that ate beetles almost exclusively) and this can
cause reduced performance, disease and even death.


The darkling beetle is the adult stage of the lesser mealworm (LMW), and is also known as “little black bug”, “litter beetle” and “Schmittle beetle.” Although originally from Asia, the darkling beetle can be found in poultry barns in every province in Canada, including the Northwest Territories.

Darkling beetles live in litter where they consume feed, manure, and dead or dying birds. They can number up to 1,000 per square metre. They are economically very costly to a poultry operation because they consume large amounts of feed, carry disease that can affect bird performance and be of a food safety concern, and can inflict significant structural damage.

The beetles are most evident in broiler chicken and turkey barns, which supply the insects’ most optimal habitat: high temperatures and humidity, litter, and an abundance of feed. They prefer wheat, broken wheat, corn and whole wheat (these are especially useful for the larval stages, allowing them to complete each stage more quickly) but they will also feed on poultry feed, flour, cereals, mixed feeds, and dead or dying animals.

These pests avoid light and are found virtually everywhere in a poultry barn that will allow them some darkness. They can survive for 400+ days and are slowed, but not eliminated, by cold temperatures.

Economic Importance
Disease Transmission
Narine Singh, On-Farm Food Safety Systems Specialist (Poultry), Alberta Agriculture, Food and Rural Development, says that by the very nature of their habitat, feeding habits, and food sources, darkling beetles become exposed to many disease pathogens, which they have been shown to disseminate to poultry. These include: E. coli (48 serotypes), several Salmonella species including S. typhimurium and S. enteritidis, Clostridium botulinum, and the viruses causing Marek’s disease, fowl pox, Newcastle disease, infectious bursal disease (IBD), and avian influenza.

Structural Pest
Late-stage larvae (called instar) search for pupation sites, and as a result migrate up into the walls and into the insulation, which provides ideal conditions for this stage of their metamorphosis.

The instar larvae can penetrate vapour barriers, perforate and damage polystyrene and polyurethane insulation, and chew the fibres (converting into a powder) of fibreglass insulation, says Singh. However, they are unable to form pupation cells in fibreglass, but can create pockets within it at the lower sections of the walls, compromising the R-value of the insulation. They are also capable of forming tunnels in drywall, panelling, wood posts and beams.

Consequently, moisture can enter into the walls and the insulation within, increasing thermal conductivity, increasing condensation on the inside of the wall, and accelerating deterioration of the building. 

To estimate the total cost of damage, Singh says the following should be taken into account: Heat loss + material cost + labour cost + loss of production cost (due to suboptimal temperature and humidity) + reduced building life + market loss (while the barn is out of production) + treatment cost + feed efficiency costs.

Food Source
As is their instinct, chickens will eat insects and larvae. Chicks are especially fond of lesser mealworms and beetles, and will consume large numbers in the first week of life, says Singh. Research has shown that in the absence of other feed, chicks exhibit reduced growth and this growth is not compensated if they are given starter feed exclusively for the remainder of their lives.

It has been observed in commercial barns that chicks will sometimes feed extensively on beetle larvae, which has been proposed as a cause of early mortality. On necropsy, Drs. Chris Wojnarowicz, M.Vsc., DVM, and Andrew Olkowski, PhD, DVM, from the University of Saskatchewan observed that chicks brought into their lab for necropsy have crops full of darkling beetles, leading them to hypothesize that darkling beetles could be eliciting a toxic effect on the birds (see the April 2007 edition of Canadian Poultry, or read the article online at

Darkling Beetle Control
Singh recommends the use of an integrated pest management program, which is a strategic combination of cultural, biological and chemical measures. Singh says that reliance upon only one of these measures to control a pest is often very ineffective and a combination should be used for maximum reduction.

Cultural Control
Cultural control involves the implementation of physical and structural measures that would decrease pest comfort, primarily by removing breeding and hiding areas (see sidebar for management control measures).

To implement physical and structural measures, Singh recommends the following: use of a heavier vapour barrier or use of a bug-resistant material; use of caulking tape between plywood sheets on the inside wall; closure of holes, cracks and crevices with a material that would resist chewing and beetle damage.

Biological Control
So far, Singh says that no known predator of the lesser mealworm has been discovered.

Recently, biopesticides have become available. Jim Skinner, president of Terragena Inc., notes that his company has been utilizing a naturally occurring fungus, Beauveria bassiana that is a host specific pathogen which targets and kills only darkling beetles.

Chemical Control
According to Singh, insecticides currently approved for lesser mealworm control are effective when used properly. This effectiveness is not only a function of the toxin, but also of concentration, treatment timing and application method.

A list of approved products should be obtained from Agriculture and Agri-Food Canada or an extension entomologist, notes Singh. Insecticides should be applied thoroughly and uniformly at the recommended rates. Singh says that as long as there are beetles present, a treatment program should be maintained. Beetle numbers are low in winter, tempting producers to discontinue treatment programs, but Singh says that this is the most strategic time to treat because it allows for quantum reduction in numbers without reinfestation from outside.

Skinner agrees that producers need to resist the urge to discontinue treatment programs. He says that as a general rule, it will take at least three flock treatment cycles to significantly reduce the number of adult beetles, but they’re never totally gone and larvae can remain. He says that he’s had customers stop treatment after one or two cycles only to end up right back in the same mess they were in before treating. “Control is something that producers must always keep on top of, every month,” he says.

Additional information and resources on darkling beetle control are available at

Management Measures for Controlling Darkling Beetles
Narine Singh recommends following these management measures to help control darkling beetles in a poultry barn:

  • Proper manure evacuation and storage.
  • Prompt removal of mortalities.
  • Composting of manure and mortalities.
  • Prevention of feed spillages.
  • High-pressure hot wash system (it will help flush beetles out of cracks and indentations).
  • Paying close attention to environmental temperature and humidity. Both of these can be used to your advantage; sub-zero temperatures will kill both larvae and adults; temperatures above 38 C will kill pupae. Beetles will migrate away from an area that is above 40 per cent humidity.
  • Avoiding mouldy litter and feed (the Aspergillus fungus produces a product that is necessary for the normal development of the darkling beetle).

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