The fly: a pest insect
The excessive presence of these insects on farms is a source of frustration for the animals. Often, in order to get rid of these unwanted tenants, the animals wriggle and kick, risking causing wounds that can become infected.The stress caused by these parasitic insects on farms reduces milk production and in general all parameters such as conversion and growth of cattle. The flies are vectors of disease, as they favor the reproduction of various bacteria and fungi harmful to the health of the animal. Flies reproduce quickly in the warm months, so it is very important to adopt techniques to reduce their presence from spring onwards.
Adopt a preventive control plan
The control of flies and blowflies in cattle farms is an important preventive measure to be carried out regularly every spring. The purpose of control is to limit the environments that favor conditions for the development of fly larvae. As far as possible, it is good to carry out a preventive control without the use of chemical pesticides, for the protection of the environment and to avoid that flies develop resistance systems to insecticides.
Before proceeding to the various actions to be taken, it is useful to program a strategic plan to be implemented, so as not to forget any detail and not to preclude any environment of the farm from inspection.
For the correct prevention of fly spread, each breeder must make sure to manage the farm’s waste, straw moisture and water stagnation in the best possible way. Ideally, good sanitation of the premises should be carried out.
Where do flies breed on farms?
Manure produced by cattle is the ideal environment for housefly reproduction because it has high temperatures, which are maintained over time. The ideal environment for fly spawning has a temperature between 35-38°C and a humidity between 40 and 80%. More than 7,000 fly larvae can live in a single kg of manure!
Damp straw is another environment that favors the development of larvae in stables.
How to prevent fly egg laying in manure?
The fly has a life cycle that can be accomplished in 7 days. Therefore, it is important to perform wet manure removal in the barn at least twice a week. Environments should be kept as clean as possible, especially in the spring.
To prevent the manure from staying wet for too long, it can be spread in fields or other outdoor areas in order to dry it out more quickly. The larvae of muscids in fact, are unsuitable to survive in dry environments.
Inside the premises, it is useful to install a ventilation system which, besides creating comfort and improving the performance of the cattle, reduces the humidity of the manure making it less suitable for egg deposition.
It is well known that areas where organic waste is present are a suitable environment for the reproduction of various pests, including flies. To avoid uncontrolled muscidial proliferation in farm waste, these areas should be controlled. Bins should have a seal to isolate their contents and be located away from areas where livestock live.
Biological control of fly proliferation
Following the logic of reducing environmental impact, it is good to avoid the use of insecticides where possible. To exterminate fly larvae populations it is possible to introduce some insects called parasitoids. They are mainly wasps that deposit their eggs in the pupae of the flies, killing them. The most suitable organisms for this purpose are wasps belonging to the genus Muscidifurax and Spalangia.
The benefit of these types of parasitoid wasps is the fact that they only attack flies, and do not bite, sting, swarm or disturb either cattle or humans. Their size is similar to that of midges. Also, because they are primarily nocturnal insects, they are rarely seen during the day.
These genera are marketed in various countries, precisely because of their usefulness in pest prevention. Generally, you purchase a lot of parasitic wasp pupae amidst some sawdust. The pupae hatch within a few days, under a light source. Once you catch a glimpse of the first wasps in the bag, it’s time to release them (ideally at dusk) around the hot spots of the barn, i.e. where the most manure is present. The selling price is around 30€ for 10,000 pupae, or 50€ for 30,000 pupae.
The ideal quantity is about 500 parasitoids per week for each cow. The operation is to be carried out during the whole warm period.
The parasitoid should be released in a given period, coinciding with the greatest spread of fly pupae in the farm. For this reason it is important to monitor the spread of flies, for example by installing adhesive sheets in indoor environments.
Fly control using parasitoids is quite effective in medium-sized environments such as stables, pigsties and dairies. In cheese production places, this method is extremely advantageous as it avoids the release of chemicals on food due to the use of insecticides.
However, it is important to note that in case of very large areas such as open fields, the effectiveness of parasitoid wasps is not adequate to eliminate sufficient groups of flies.
|Harmless to humans and cattle||Need for weekly distribution of parasitodides|
|Relatively low cost||Low efficacy in extensive livestock and outdoor fields|
|Non-chemical||difficult to find commercially in some areas|
Actions to be performed after reduction of muscid larvae
It should be remembered that, effective preventive control of fly larvae should be effective for a marked decrease in the population during the warmer months. However, additional measures can be taken to exterminate adult flies without the use of insecticides.
In late spring and summer, adulticide traps can be installed to decrease the spread of the fly on farms. These are primarily systems that exploit positive phototropism, or the attraction of flies to light sources.
Adult pathogenic insects can be captured in a variety of ways by attracting them to electric grids, sticky surfaces, or fans through light lamps.
In the United States, a type of trap in which the cattle must pass inside a narrow covered structure is relatively popular. The animal crawls its fur over the walls covered with some brushes that allow it to capture flies in large numbers. The insect, once removed from the fur and trapped by the brushes, will look for the outside light to get out, where it will find a net that will not allow its exit.However, the disadvantage of this type of structure lies in the difficulty to herd the cattle inside. For this reason, the use of this type of traps is less and less frequent.
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