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Act early to control flies this summer

AlisonFlies are a huge problem on poultry units over the summer – but by acting early producers stand the greatest chances of successfully controlling them. Alison Colville-Hyde, Field Services Manager, explains how.

Summer is on its way, and with it the inevitable seasonal pest: Flies. Always a challenge for poultry producers to control, flies can carry disease and irritate the chickens, so it’s essential to act early to prevent the population getting out of hand.

Chemical controls can be expensive, bad for the environment, and of course are prohibited on organic units. But there is another, effective option: Parasitic wasps. An increasing number of free-range poultry producers are using these little creatures to tackle flies in their sheds.

The adult wasps – which are the size of a gnat – lay a number of eggs inside fly pupae, preventing them from hatching into flies. Here at St David’s we have been selling parasitic wasps for a number of years and we know they work. But this year we have changed species to a more prolific one, capable of laying multiple eggs in each fly pupa. Wasps are supplied in cardboard tubes which treat 3000 birds, so it’s very easy to calculate how many you need.

Flies proliferate in warm, moist environments with ready food sources, so the key on any farm is cleanliness. Clean up spillages, try and keep the litter in the pit dry, and store or spread manure well away from neighbouring properties and poultry sheds.

However, no amount of cleaning will prevent an explosion of flies if the weather is against you, so additional action is required. On an organic system there aren’t many knock-down chemicals or larvicides you can use, so it’s all about preventing ingress of flies to the shed in the first place.

But even on non-organic farms, the use of chemicals is under intense scrutiny, and flies can develop resistance to some chemicals, which is becoming a worry on some farms. With parasitic wasps – which are fully approved and EU-bred – there’s no threat to the environment, humans or birds; it’s a cost-effective and low-impact alternative.

All farmers need to do is sprinkle the wasps – which arrive unhatched within fly larvae – through the slats onto their poultry manure. You need to have three to four weeks of litter built up, as the larvae need warm, moist conditions to hatch.

wasp3Once mature, they mate and inject their eggs into more fly pupae. They don’t come up above the slats, so they don’t irritate the birds, and once the temperature drops below 15C they will gradually die off. As they’re more prolific than the old species we used, you only need to reapply once a month rather than once a fortnight, which is a good saving.

However, it’s important to get the wasp population established before flies become a real problem. Parasitic wasps also only work against fly pupae, so you’ll need to use other measures like fly paper and ultraviolet fly killers inside egg rooms, with pheromone traps outside the house to control adult flies. And remember not to use chemical controls as that will kill off your wasps too.

Each site is likely to require a different approach, dependent on house structure, number of birds, age of flock and any particular fly issue. At the end of the flock farmers can spread the litter on land as normal – and on mixed farms they can even add the wasps to livestock manure to further control fly populations around the farm.

  • To order your parasitic wasps, call St David’s Poultry Team on 01392 872932.

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