Nuisance Insects in Organic Poultry Production

The summer of 2013 has many farmers noticing increased insect pest issues in their area. On occasion, these insects issues have caused increased tension among neighbours (high fly populations), and increased disease challenges (high darkling beetle populations). Some are suggesting that the weather this spring and summer so far - with high amounts of heat and moisture - could be contributing to the problem. Infestation with insects is an issue in the industry regardless of your production status as an organic or conventional poultry farmer. For this article, we will be discussing the biology, management, and control measures for flies and darkling beetles.

Regardless of the pest species, dealing with the problem is all about understanding the biology of the insect itself, and managing the population according to their life cycle. Pest management will not be as effective if you simply stick to a routine that's more convenient for you. It is also critical that you are aware that the problem goes beyond what you can see, as there are many insect life stages that are not visible to you. For example, the adult flies that you can physically see in your barns are a mere 15% of that total fly population. If you are not considering all stages of the life cycle in your control program, you may suddenly be faced with an infestation when adults emerge in droves. For this reason, understanding aspects of the insect's reproduction, behavior, habitat, and seasonality is essential.

Alphitobius diaperinus, also known as the darkling beetle is one of the most common pests found in poultry barns. The adult beetle is shiny brown or black in colour, and approximately 6 mm long. The larvae, (or grubs), can grow to 1 cm in length before they pupate. The darkling beetle goes by many other names, including the lesser meal worm, litter beetle, shining black wheat beetle, and black fungus beetle. This beetle traditionally consumes grain, however, poultry barns have provided an ideal environment for it to flourish, as it can survive on spilled feed and manure underneath feed lines.

The success of this insect's life cycle is dependent on temperature, humidity, moisture, and food availability, with cycles ranging anywhere from two months to 400 days (See below).

Life Cycle of the Darkling Beetle

  • Non-mobile
  • Females lay eggs in litter which hatch in approximately 45 to 100+days
  • Mobile
  • Burrow into the earth floor and insulation to pupate 35 to 100+ days
  • Non-mobile
  • 90 to 140 days beetle to emerge
  • Mobile
  • Live 60 to 400 days
  • Produces 200-2,000 eggs

*Time dependent on temperature and humidity

During this time, females can lay an average of 5 eggs per day in their reproductive prime. Considering many poultry barns are home to thousands of darkling beetles at a time, the reproductive potential of this insect is astounding if conditions are optimal. A new adult darkling beetle can emerge only 29 days after an egg is laid. The highest hatchability of darkling beetle eggs occurs at 30 C and 90% humidity. After hatching, the beetles can remain in the larval stage for up to 133 days. Newly emerged darkling beetles have a reddish colour that will become darker as they age. They can reproduce almost immediately after emerging. At some point during your poultry flock cycle, beetle larvae will begin to seek sites to pupate, and re-emerge at a later point, which could coincide with a succeeding flock. When birds are shipped out and the barn is empty, adult beetles will seek shelter in walls and under the floors. They too will re-emerge.

The darkling beetle poses an economic threat to poultry farmers on several levels. Firstly, these insects cause structural damage to insulation when they burrow into walls to pupate. Such damage can decrease the insulating ability of poultry barns. By burrowing through materials such as styrofoam, these beetles can decrease the effectiveness of insulation by as much as 30%. In Georgia, USA, insulation deterioration from darkling beetles can result in as much as a 67% increase in energy costs required to keep the barn at an appropriate temperature.

Secondly, darkling beetles pose a significant threat to biosecurity. Their 400-day lifespan could extend over several flocks. Darkling beetles are known vectors of 60 or more diseases that poultry are susceptible to, such as Newcastle disease, avian influenza, Marek's disease, infectious bursal disease, Salmonella spp., 26 pathogenic types of E. Coli, Eimeria spp., Aspergillus, and parasites such as coccidiosis and round worm. Both adult and larval darkling beetles can harbour disease, carrying pathogens in their gut and on their bodies. Studies have shown that darkling beetles can remain positive for E. coli for up to 12 days, and salmonella for up to 28 days. These time periods are sufficient enough to allow infection of a subsequent flock. It also should be noted that infected larvae can become infected adults.

Transmission of salmonella from darkling beetles to young chicks has been well documented, and these chicks will then proceed to spread the bacteria to others. It has also been shown that birds can become infected after ingestion of a single contaminated darkling beetle. Ingestion of these beetles can also impair flock performance. As darkling beetles live around feed lines and feed pans, chicks and poults often choose to feed on darkling beetles first, and feed second (Fig 1.)This fills their gut volume with indigestible beetle shells instead of feed, and can cause distress to the birds when they defecate. In addition, darkling beetles act as an intermediate host for poultry tapeworms which can further reduce performance.
Fig.2 Darkling Beetles in Crop of Broiler Chicken- courtesy of Jim Skinner

Fig.1 Darkling Beetles in Crop of Broiler Chicken- courtesy of Jim Skinner

In severe infestations, if these beetles cannot find enough moisture in their environment when humidity in the barn is low, they have been known to bite birds around their vents and feather follicles. This can cause tissue damage and infection. Lesions from darkling beetle attacks can look similar to skin leucosis.

Darkling beetles can be problematic for human health as well. People that are continuously exposed to high numbers of darkling beetles can develop allergies. Neighbourhood relations could also be jeopardized in areas with an infestation of darkling beetles, as the beetles will remain in the manure when it is spread onto cropland. Being nocturnal and attracted to both light and heat, these beetles can fly or crawl out of the fields towards adjacent residential areas in search of a new home.

Elimination of a darkling beetle population is practically impossible. Though many farmers may assume that cold Canadian winters will kill off these insects, darkling beetles are surprisingly resistant. During cold weather, darkling beetles can undergo 'supercooling,' where their body fluids resist freezing solid, allowing this tropical beetle to survive in spite of the cold. Dissolved sugars in the beetle's hemolymph allow beetles to survive long winter months when there may not be birds in the barn as their metabolism runs at much slower rate. We tend to see the heaviest infestations of darkling beetles in the fall as they seek out shelter and warmth as the external temperatures fall. If they do not find these conditions, they may be able to survive in this hibernation state.

As an organic producer, there are limited options for darkling beetle management. These options include cultural and biological methods. Cultural strategies include mechanical upkeep of equipment to minimize excess litter moisture caused by leaky water lines and improving ventilation can reduce darkling beetle reproduction in your barn. Removing litter between flocks can also help to reduce beetle build up. Furthermore, avoid equipment sharing between neighbours and barns to prevent mechanical transmission of beetles.

Biological methods generally have poor success with a couple of exceptions. Predatory insects, parasitoids, and nematodes have not been commercially viable options for organic farmers. Diatomaceous earth (silica sand) is made up of tiny, sharp diatoms that, when the insect crawls through, will compromise the beetle's waxy cuticle. This leaves them vulnerable to desiccation and infection. Since the beetles need to crawl through it to be effective, diatomaceous earth should be spread where there is high beetle traffic on the floor along walls and posts, and cracks in the cement.

The biological agent that seems to be the most effective against darkling beetles is the fungal pathogen, Beauveria bassinana. This fungus infects both juvenile and adult stages of the beetle. The spore of the fungus will adhere to the insect and germinate, with hyphae extending into the body cavity to cause death.

Musca domestica, known as the common house fly or 'filth fly', is a prevalent nuisance species among all poultry production. Adults are under 3/4 cm in length and do not bite (Fig. 2). They breed and feed in warm, moist, organic material, and females lay 500 to 1000 eggs over her life time of three to four weeks. The life cycle (egg-to-egg) of the common house fly averages 21 days in length, though can be shorter or longer during higher and lower temperatures, respectively. Eggs hatch within 24 hours. The juveniles, or maggots, will undergo three instars (shed their skin as they grow) over 4 to 7 days and then pupate into an adult.

Fig.3 Life Cycle of the Common House Fly

Fig.2 Life Cycle of the Common House Fly

Flies, like darkling beetles can be a serious biosecurity risk as vectors of diseases such as Salmonella enteritidis and E. coli. One study documented flies that remained positive for salmonella for upwards of 7 days. Flies can also potentially be mechanical vectors of many other diseases as well.

House flies can be a nuisance to poultry and people alike. High fly infestations can cause stress among birds, resulting in production loss, whether it be meat or eggs. As a farmer, high levels of flies can make the barn uncomfortable to work in and potentially cause tension with neighbours. Flies can also pose a food safety concern, as eggs just laid by the hen are moist and warm, making them attractive to adult flies. These flies can transmit pathogens to the surface of the egg, which can then be drawn into the egg as the egg cools.

When it comes to dealing with fly infestations, there are cultural, physical, and biological methods of management. Success of fly management hinges on locating fly breeding grounds and eliminating them.

Cultural methods aim to reduce litter moisture or changing litter pH. Flies will lay eggs in organic matter that is between 20 and 80% moisture, with 60-80% being ideal. The drier the manure, the fewer flies you will have. Therefore, controlling water leaks and spills and ensuring proper ventilation can have a huge impact on your fly population. You must also minimize breeding and feeding sites around your property such as rotting vegetation, garbage, spilled feed, livestock manure, and long grass. Boric acid, citric acid, and lime will change the pH of the litter, making it inhospitable to fly development. However, this is only recommended if the manure is separate from the birds, i.e. slatted floors. Otherwise, acidic or caustic conditions can burn foot pads.

Physical control methods include sticky traps, bag traps, and light traps (attractants and bug zappers) to reduce adult populations, as well as proper manure composting to kill larvae. Sticky traps must be monitored and replaced frequently as they fill with dead flies or become covered in dust and dander. Bag traps must also be monitored to make sure they do not become too full. Light traps use UV light to attract flies, becoming less effective when they are dirty. Be cautious when using light traps, as they could potentially short out, and become a fire hazard. Also, little is known about the effects of UV light on poultry behaviour.

When manure is composting internal pile temperatures can reach temperatures in excess of 55C - hot enough to kill fly larvae. However, the exterior of the pile can be much cooler, causing larvae to migrate to the outside and complete their life cycle. By physically mixing and turning the pile, you will ensure that the outside of the pile (and any fly larvae and pupae) are also sufficiently heat treated.

Biological control methods include: parasitic wasps, nematodes, mites, hister beetles, earwigs, and certain fungi. When using any biological species, you need to start your program early - biological populations cannot increase as quickly as the fly population. It is also important to continue treating with biologicals even when you do not see adult flies present to keep the population suppressed.

There are ways to effectively manage darkling and flies without the use of chemical pesticides. However this requires a basic understanding of insect biology, monitoring, and both cultural and biological control methods. To quote Jim Skinner, CEO Terregena Inc.: "Pest control is a science. It is not some sort of trial and error, and if you think in terms of a scientific solution to addressing the pest problem, then you can get to where you want to go."

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