What have the flies you see buzzing around your animals and icebergs got in common? The answer, the greatest danger comes from what lies beneath!
Just like the tip of an iceberg only 15% of your farm fly population can actually be seen, the remaining 85% is hidden away as eggs, maggots and pupae waiting to wreak all kinds of havoc on the health of your livestock and the profitability of your business.
So how do we prevent this iceberg sinking us? Firstly, know your enemy.
Nuisance flies fall into two distinct groups, biting and non-biting. The non-biting group consist of the House Fly, Head Fly and Face Fly. These flies feed on body secretion and tend to be attracted to the muzzle and eye areas of livestock where there is always an abundant food source. These flies are not fussy eaters and will quite happily move restaurants should other goodies like pus, blood or milk become available. It is because of their choice of fine dining this group of flies are mostly associated with transmitting two commonly seen diseases in summer grazing cattle, New Forest Eye and Summer Mastitis. Both are distressing for the animal and costly to your business.
The biting flies most commonly associated with livestock are the Stable Fly and Horn Fly. These flies tend to be seen later in the season, July-September. Stable flies are usually found on the legs and underbelly and will take a blood meal only once or twice during the course of a day, spending the remainder of the time resting in the shelter of bushes, buildings or on fences. The Horn fly on the other hand will spend the entire day on its chosen meal and can be seen predominately on the backs and flanks of animals. This fly will take in excess of 20 blood meals a day and if the population goes unchecked are capable of draining 200ml of blood, per animal per day.
As with any insect which takes a blood meal from its host there comes a risk of disease transmission, warts being the obvious where these flies are concerned. Without doubt the greatest risk posed by this group is the extreme irritation and stress their biting causes, resulting in a great deal of lost grazing time. It has been found that high populations of these flies can mean a milk loss of up to 0.5kg/cow/day in dairy herds and reduce DLWG (Daily Live Weight Gain) in beef herds by 0.28kg/head/day. That is as much as 130kg of milk and 26kg of growth over the summer grazing season. You do the maths for your herd!
Both species life cycles start as an egg laying female. A female can lay up to 900 eggs which she deposits in warm, moist areas high in organic matter, areas such as slurry lagoons, dung heaps and calf pens for example. Within hours the eggs hatch into tiny white maggots which in turn will pass through three growth stages before becoming a pupa and eventually hatching out as an adult fly, instantly able to mate, lay eggs and start the whole cycle over again. The actual time this process takes is solely dependent on temperature but at the height of summer with average temperatures of above 25°C a fly can go from egg to emerging adult in as little as eight days and each one capable of producing anything up to 12 generations in their lifetime.
So as you can see, things can go from a minor nuisance to an epidemic of biblical proportions in a relatively short space of time.
So how do we stop this happening? By breaking the cycle.
There are two ways of breaking the cycle, Environmental Control and Chemical Control. Both if implemented individually will go a long way to reducing your resident fly population and so reducing the risk of disease and production losses. Combine them, you have a powerful weapon against this underestimated foe.
Each fly species population will peak at different times during the summer. The Head Fly in May, Face Fly in June, Horn Fly July, Stable Fly August-September – so the object of the exercise is to prevent these peaks occurring.The most effective way to control adult populations is the application of pour-on products, Chemical Control, such as Spotinor early in the grazing season. Applying a pour-on right at the beginning of the summer period and topping up at regular intervals throughout the grazing season will have the effect of reducing each of the species breeding populations as they emerge. This will effectively flatten population peaks to more tolerable levels. A pour-on is not a repellent, it does not form an impenetrable barrier around your animals, the fly must land, come in contact with and absorb the active ingredient to kill it. It therefore follows that every time a fly pitches on a treated animal, it absorbs a small amount of insecticide and the concentration left on that animal becomes weakened. This is why when faced with an epidemic, you do not get the full length of cover claimed by the pour-on manufacturer. It’s not that the product is not working but simply it’s being taken up faster by high fly challenges. This is another good reason to start a pour-on strategy early, because a reduced resident fly population means a greater period of efficacy from your chosen product.
And now for that unseen 85%, this is where you can really make a difference to the resident population – Environmental Control.
The most cost-effective method of any on farm fly control programme is cleanliness. No breeding sites, no flies. It’s that simple!! Dung heaps; areas missed by scrapers; poorly managed silage clamps; waste feed around troughs; anywhere where organic matter is left long enough – make life comfortable for the up and coming fly populace and should be kept to an absolute minimum. If it’s impractical to store organic waste away from farm buildings then you could try covering it with plastic sheeting, this will take the temperature of the heap beyond tolerable breeding levels.
Another, sustainable alternative? Parasitic wasps! They are tiny, closer to midge size than a fly and they don’t sting. The adults kill nuisance flies by laying eggs in pupae around the environment. The wasp eggs hatch within the pupae, consume the larvae (killing them), before hatching out to fly around laying more eggs in more pupae. Considering 80% of nuisance flies on your farm are in pupae/maggot form, it makes sense to kill them before they hatch and become a nuisance to your animals.The secret to their success is spreading parasitic wasps before the nuisance flies hatch… and not stopping until late autumn. Ideally wasp orders need to be in by March, so we can get them out to farm before nuisance flies emerge! For more info please contact Dispensary, even if preparing for next year and beyond.
In conclusion like any other health risk, prevention is always more cost effective than a cure, so the best way to avoid an iceberg is to implement the three R’s.”
REDUCE the emerging adult breeding population.
REMOVE as many possible potential breeding sites as is practical.
RESTRICT the amount of emerging adults from unavoidable breeding sites.
Barry Ewens – Synergy Farm Health, RAMA
