That the fly plays an important role in nature is not to be questioned, but they can still be a terrible nuisance. Although flies can never be eradicated, they can still be brought under control, if things are done correctly.
Biological control
Why?
Especially dairies, meat and egg producers are expected to change over to alternative methods to chemical control. Control which focuses on the adult fly cannot be effective, because by the time fly control measures have been implemented, you probably have a 60% chance that she has already laid her 900 eggs.
How?
Muscidifurax raptor and Nasonia spp.
These wasps (parasites) attack up to 10 different kinds of flies, including blowflies and horse flies.
They are already 100% acclimatised to our climate and are currently being increased in our country in insectariums.
Habitat
The wasps prefer areas such as damp dung heaps, wet feed, compost heaps, where water is leaking or any place where flies breed. They get released in their larval stage into the fly pupa, which they then parasitise and complete their life cycle in the pupa.
At chicken runs the parasites can be hung up in bags to prevent them being pecked up.
What does it look like?
The wasps are black and approx. 2 mm long.
Both types of wasp are nocturnal, ant-like and prefer to walk rather than fly.
The life cycle of the wasp is about 3 - 4 weeks.
They can move about 30 - 50 meters and parasitise or mutilate about 100 pupa.
Life cycle of the wasp parasite
The parasite lays its egg inside fly pupa; egg inside fly pupa; 3rd stage larvae of parasite inside fly pupa; parasite pupa inside fly pupa; adult parasite leaves fly pupa; adult wasp parasite.
NB The parasite cannot become an invader as it parasitises fly larvae and fly pupae, after which it dies at the end of its natural life cycle of 3-4 weeks. (Should they eradicate all flies their life cycle cannot be completed ending the population.) They are also endemic.
Fly Facts
Flies can move between 8 - 14 km per day.
A female can lay up to 900 eggs in her lifetime of up to 30 days.
Under optimum conditions the fly can complete its life cycle in 8 days.
Flies are carriers of more than 20 different diseases such as gastro-enteritis, polio, typhoid, pink-eye, tuberculosis, Newcastle disease, etc.
Cattle use up to a third of their energy to chase off flies which causes a decrease in production of meat and/or milk.
Horses get desperately frustrated by flies resulting in decreased growth and reproduction.
Disadvantages of chemical control
Chemical control gets more expensive every year and less effective as resistance develops.
Rain and the use of water eliminate the effectiveness of chemicals.
It can cause pollution and contamination of water.
It often kills the natural enemies of flies.
Residues have been found in milk and animal hides – health authorities are already very sensitive about it.
Workers' unions are dissatisfied with the use of chemicals near workers.
More and more pressure from supermarkets and import countries with control measures like EUREPGAP that oblige producers to use less chemicals.
