Controlling Flies on Poultry Farms05 May 2014
Byron Stein, Editor of 'The Drumstick' in Australia talks to Dr Garry Levot from New South Wales Department of Primary Industries (NSW DPI) about the flies commonly affecting poultry farms and how to control them.
A recent outbreak of flies in ‘biblical proportions’ on a poultry farm in New South Wales, led to major issues for the poultry farmer and for his neighbours. Complaints from ‘less-than-impressed neighbours’ were made to council, DPI, the Livestock Health and Pest Authorities and other agencies. What made this case particularly concerning was that the fly ‘outbreak’ was in winter, not a typical time for large fly numbers.
So what might have caused this and what could the farmer have done to quickly knock down the fly problem and stop his telephone ringing hot with loud angry voices on the other end?
This article aims to provide guidance on how to control nuisance flies by briefly outlining:
- the main pest fly species and some of their characteristics
- how biological control agents can be protected and encouraged
- how farm management can be modified to reduce fly breeding, and
- how and when registered insecticides should be used for optimal effect.
Nuisance fly numbers can quickly build up when they have access to litter, spoiled feed and bedding material. Depending on the situation several species may be involved. Most are just an annoyance to stock and workers but those that bite can irritate animals such that production may be affected. There may also be a risk of disease transfer associated with fly plagues.
Primarily however, the presence of large number of flies can irritate farm workers, affect produce, cause neighbours to complain and affect the reputation of the farm, so good farm management must include effective fly control.
Some level of fly infestation is inevitable on poultry farms but fly numbers in pest proportions usually indicate a failure in one or several key areas of farm management. The most common reasons are:
- inadequate manure management
- excessive moisture levels in and around sheds
- failure to clean up spilled or spoiled feed or soiled straw bedding
- poor management of compost piles
- ineffective use of pesticides - using the wrong insecticide at the wrong time of year against the wrong fly species, or overusing chemical pesticides leading to resistance
- lack of understanding of fly breeding habits
- poor maintenance of buildings or services such as watering systems
One of the most important tips in effective fly control is: ‘know which ones you are dealing with’. Not all flies are made equal, and one of the most important lessons is to know which fly, or flies, you are dealing with. This is especially important because house flies have developed resistance to some insecticides whereas other common nuisance flies have not. Failure to select the most effective treatments is likely to lead to poor fly control and wasted money and effort.
What Are the Contenders?
The following table lists the most common fly species associated with poultry farms. It includes the three major fly pest species as well as six of the minor or occasional fly species which may sometimes also cause problems when conditions and seasons suit them.
As noted previously, it is really important to know which of the above flies is bugging you and your birds to effectively control the flies and ensure you get the best results. Like you, I’m no fly expert, and one fly looks about the same as every other one splattered on my swatter. So how can you realistically figure out which of the above flies is causing you issues.
In response to Mr Stein's request for advice, Dr Levot said: “In springtime, it is most likely to be the stable fly (Muscina) which is the bigger and slightly brown fly and the lesser house fly (Fannia), which is smaller, black and constantly flying in circles.
By mid-summer, the house fly (Musca) turns up. It is smaller than the stable fly and bigger than the lesser house fly. The stable fly pretty much disappears by mid-summer.
Whereas most entomologists might, as a matter of course, not leave home without their butterfly net, Mr Stein says very few chicken farmers share their enthusiasm for catching bugs. For these people, the best option is to pick flies out of fly bait trays (use gloves to avoid touching insecticide), put them in a plastic sample jar and send for full identification.
What to Do about the Flies
Once you know which flies you are dealing with, what can you do about them?
Fly control can only be achieved by an integrated pest management approach. This essentially means doing a range of things rather than sticking to just one control method, which is seldom effective on its own.
Four basic principles apply:
- It is impossible to eradicate all flies, so control practices are directed at reducing fly populations to tolerable levels.
- There are many beneficial insects and mites that assist in fly control. The control provided by these is called natural, or biological control and is free! Good farm management will preserve these beneficial predators and parasites.
- A good standard of farm management will reduce fly populations and the need to use insecticides. Good management includes general farm hygiene, maintaining healthy animals, trimming grass around sheds, cleaning up spilt feed around storage areas and animal sheds, reducing moisture in and around buildings by controlling water run-off, guttering, drains and maintaining leak-free stock watering systems.
- Despite all management effort, under certain environmental circumstances fly numbers can increase considerably. This occurs most often in spring when false stable flies multiply but may also occur during warm, wet summers when the excess moisture prevents manure drying and favours rapid fly breeding. At these times insecticides may be needed to reduce the population of flies to tolerable levels.
Biological Control: Bugs versus Flies
There are a range of bugs that do a great job on nailing fly eggs and larvae and can be a very effective part of an overall management strategy.
Among the most common predators are the beetles Carcinops pumilio, Creophilus erythrocephalus and Alphitobius diaperinus. Carcinops adults and larvae are commonly seen in manure searching for fly eggs and larvae. Adult beetles will eat up to 24 fly eggs per day.
The Devil’s Coach horse (Creophilus) beetles are very active predators of fly maggots in intensive livestock facilities. They are also very commonly seen feeding on maggots in carrion.
These are ‘good mites’ and should not be mistaken for poultry red mites or northern fowl mites that are blood-sucking parasites of hens.
The predatory mites are found in the manure and on adult flies. They are not insects but are beneficial organisms closely related to spiders that feed on fly eggs and very young fly maggots. Three families of these mites are represented in poultry sheds: Macrochelidae, Uropodidae and Parasitidae.
As manure accumulates, parasitids are the first group to arrive, followed by macrochelids and finally uropodids. The macrochelids are often very abundant in poultry manure. The female mites attach to flies for transportation to new areas. Substantial reduction in fly numbers because of macrochelid mite predation has been demonstrated. Whereas the macrochelids are active on the manure surface, uropodid mites feed on larvae deep within accumulated manure.
These are all tiny wasps belonging to the families, Pteromalidae or Chalcididae.
One of the most commonly used of these wasps is Spalangia endius. Spalangia are tiny wasps (2 to 3mm long) that are naturalised to Australia.
They are parasites of certain fly species, including the house fly and stable fly. Spalangia are harmless to other insects and to all vertebrate animals including humans.
Depending on species, female wasps deposit one or many eggs into pupae or full-size fly maggots. By their feeding the wasp larvae that hatch from the eggs destroy the developing fly and emerge from the fly puparia as adult wasps three weeks later. Parasitism rates as high as 40 per cent have been recorded.
Under normal conditions, a balance is reached between flies and the predators and parasites that naturally regulate population size such that flies do not reach pest levels. For this reason, it is essential that the preservation of beneficial organisms be considered in farm management and especially when using insecticides. Increases in the populations of predators and parasites always lag behind those of the pest and are usually at a slower rate than those of the flies. Complete removal of accumulated manure can also remove many of the predators and parasites. If you remove manure from all rows, leave a pad of manure 2 to 3cm thick to help preserve the predatory beetles and mites and the parasitic wasps.
One of the commercial suppliers of biological control agents is Dan Papacek from Bugs for Bugs. Their web site gives details about the bugs they have to control flies, when and how to use them and their costs.
Use of Insecticides
There are dozens of chemical insecticides registered for use in and around sheds to control nuisance flies. These products can be segregated into different insecticide classes depending on the active ingredient they contain.
They can also be segregated on the basis of how they are formulated. For example, there are wall sprays, fly baits, a feed additive and topical manure sprays. Each product has particular properties, which means that the effectiveness of each product will differ depending on the species of fly present, shed construction or the timing of the insecticidal application. For example, some fly bait products contain a pheromone that is only attractive to house flies. Smooth, impervious walls such as galvanised iron will retain a surface treatment well whereas insecticide sprays applied to concrete walls are much less effective.
Depending on the product chosen, baits can be scattered on the ground or mixed with water and painted on surfaces, however, it is preferable to sprinkle baits onto damp hessian contained in dedicated bait trays that can be deployed where most effective.
For the current list of products registered in Australia, go to www.infopest.com.au or check with the Australian Pesticides and Veterinary Medicines Authority. Always follow the instructions on the product label including the precautionary advice on the use of personal protective clothing.
Total reliance on insecticides for fly control is unsustainable and has a number of disadvantages. Apart from the financial cost of the products, there are costs in terms of time and labour, occupational health and safety considerations and the capital investment and maintenance costs for spray equipment etc.
There are two major risks associated with excessive or inappropriate use of insecticides:
- Insecticides also kill the beneficial insects and mites, particularly parasitic wasps. This reduces the effect of biological control and can create a persistent fly problem.
- Insecticide resistant flies may eventually build up in the population.
When a new insecticide is first used against an insect pest such as the house fly, the population of the pest in the treated area is drastically reduced if the product has been applied correctly. However, a small proportion of individuals that have a greater ability to withstand the effects of the spray will survive. These insects may survive and breed, resulting in a rapid increase in fly numbers. Under this scenario many producers will apply multiple insecticide treatments. With each treatment, the proportion of survivors will increase until the insect population is largely unaffected by the insecticide.
Research has shown that Australian house fly populations contain flies resistant to several insecticides, whereas false stable flies and lesser house flies are not yet resistant.
This means that if the wrong insecticide is used resistant house flies are likely to survive a spray or bait treatment and continue to breed. Differences in susceptibility to the various registered insecticides among the common fly species means that control strategies should take account of the fly species targeted by selecting product(s) that are most likely to have maximal effect.
To reduce the risk of resistance developing, it is wise to rotate the use of insecticides to minimise fly exposure to any single insecticide class. This can be achieved by alternating the use of products belonging to unrelated insecticide classes irrespective of whether a wall spray or a fly bait is chosen.
Just remember to ensure that you are using the right mix of pesticides registered for use for the fly species you are trying to control.
You can view the full factsheet from the New South Wales Department of Primary Industries by clicking here.