Tina Andersen

Fall and Winter are low seasons for flies. It can be tempting to cut back on all the fly control work in the stables and enjoy the low number of annoying flies. But you would be wise to plan the coming year’s fly control in the Fall/Vinter, because once the heat comes in the new year so too will the flies be back.

As it gets warmer the flies reproduce more rapidly and what is called fly season is usually from March/April till October/November in Denmark. During the winter period the number of flies drops as the temperature does, and it is easy to forget how much unwanted flies can torment animals and humans in the stable.

 

Some people wait until spring to decide how to handle fly season because they “want to wait and see how bad it gets” but that can become expensive, you can read more about that in the articleLandmand og snart forår? Forbered dig til fluesæsonen nu.

It’s easier to prevent than to cure

As spring comes around, so does the word in the fields and time starts to run out for deciding on the fly control for the season. And if too much time passes and the unwanted flies manage to establish themselves in the stable, you will have to work much harder to bring the population under control. As a basic there are two strategies for getting control.

1. strategy: Treat the symptoms with fly poison

You can choose to control the grown flies as the emerge by using immediate agents such as fog sprays, for example Aquapy (Aerosol containing poison), or alternatively something like Agita which you can smear on your walls – Agita contains a sugary lure and has an immediate effect that can last for up to 4 weeks.

2. strategy: Preventative treatment with either fly poison or biological fly control

To actually get control of the flies and not just treat the symptoms of the problem, when the flies have already started hovering around the animals it is necessary to control the population before they develop from the larvae stage into flies

Prevention with poison

Before the start of the fly season, you can work preventatively using larvacids such as Neporex or Hokoes, both of which contain poison that targets the fly larvae. The agent is sprinkled or dissolved in water and watered along the edge of the box you want to treat. In stables with slatted floors and pig stables the entire surface of the floor must be treated.

• • • Pros
      • Effective treatment against house flies and biting flies
      • Larvaecids have not shown any signs that the larvae can develop resistance
    • Cons
      • No immidiate effect on grown flies. You could complement with a smear that has good effect against adult flies
      • Effect lasts for about 14 days after first treatment
      • Larvaecids cannot be used by organic farmers
      • The treatment has to be repeated all of the fly season (according to data sheet: about 13 times

Prevention with biological fly control

If you choose to prepare for the fly season and want to spend minimal time and effort on fly control, then biological fly control may be the way forward for you. This treatment solution involves deploying predatory flies or mini wasps to the stable environment in early spring. Both of these are natural and effective enemies of the common house fly and the biting fly.

• Pros

• • Effective against the common house fly and biting fly
  • Subscription solution with a delivery plan for the fly season. The products are delivered directly to the stables when it’s time to deploy them
  • Preventative and holistic solution for the whole fly season
  • Minimal workload in the stable. The products are hung in complimentary buckets or added directly to the stable environment at recommended locations when they arrive

• • No risk of anything developing resistance to the method
  • can be used by organic farmers

• Cons
  • No immidiate effect on adult flies
  • It takes about 4-6 weeks before the effect of the predatory flies and mini wasps really kicks off. This is why it’s a good idea to start using them before the fly season really gets going
  • The treatment has to be repeated throughout the fly season (6-11 times – depending on the situation in and type of stable)

 

Predatory flies are used for controlling the population of other flies in pig and cattle stables. Its larvae eat the larvae of other flies. They are good for controlling the population of other types of flies in stables with for instance slurry channels. Source: Predatory flies by subscription. Miljøfluen

 

Mini wasps are a small group of wasps that breed by laying their eggs in the pupae of the flies. They are good for controlling the fly population in stables with deep litter bedding. They arrive in sealed containers to the stables. The wasps need to get into the bedding to find the fly pupae containing the unwanted flies. You can either spred the mini wasps in the bedding or place the opened container close to the area you want fly control in. Source: Mini wasps by subscription, Miljøfluen

 

Deploy the predatory flies or the mini wasps in the stables in early spring before the heat sets in to keep unwanted flies under control from the beginning of the season. Start early with a few deliveries and experience that you can keep the number of unwanted flies low for the whole season.

Sources

Andersen, Tina (2022) Farmer, and spring is closing in? Prepare for fly season now. MILJØFLUENS DATABANK ABOUT BIOLOGICAL FLY CONTROL

Andersen, Tina (2021) Flies can develop resistance to fly poison (Insecticides) MILJØFLUENS DATABANK ABOUT BIOLOGICAL FLY CONTROL
Nachman, Gösta & Skovgård, henrik (2016) Fluesimulatoren. Aktuel Naturvidenskab. Nr. 4.

Skovgård, H. (2004) Sustained releases of the pupal arasitoid Spalangia cameroni (Hymenoptera: pteromalidae) for control of house flies, Musca domestica and stable flies Stomoxys calcitrans (Diptera: Muscidae) on dairy farms in Denmark. Biological Control, bind 30, s. 288-297

Miljøfluen (2023) Predatory flies by subscription. http://www.miljofluen.dk

Miljøfluen (2023) mini wasps by subscription. http://www.miljofluen.dk

To put it in simple terms, biological fly control is the term for the method of using the natural enemies of the flies for keep the population under control. Several insects are so-called beneficial insects and will exterminate other insects such as house flies and biting flies. An example of the is predatory flies and mini wasps, and as such these can be used strategically for example as natural fly control in cattle, pig and horse stables.

Biological fly control is a preventative method for fly control

To make use of biological fly control using predatory flies or mini wasps, it has to be considered a preventative strategy meaning the plan for fly control should be initiated in early spring, as it is important to be aware that you have to start BEFORE the heat of spring and summer arrive.

Spring: Establish an army of beneficial insects in the stable

A small army of predatory flies and mini wasps should be established in the stable, before the unwanted flies show up. In that way you will be ahead of the development and the stable will be ready for deling with the invasion of flies.

Summer: Deploy small portions of beneficial insects in the stable throughout the summer

By deploying portions of predatory flies or mini wasps in the environment of the stable with short intervals in early spring and regularly throughout summer it becomes possible to keep, for instance, the common house fly and the biting fly populations low for all of the fly season.

Biological fly control can be used with great success in pig and cattle stables

In 2014 the Department of Agroecology at Aarhus University wrote Guidelines for control of flies at and around farms with livestock. They have noted the following about biological fly control:

“BIOLOGICAL CONTROL OF FLIES USING PREDATORY FLIES CAN BE USED WITH GREAT SUCCESS IN MANY PIG STABLES WITH SLOTTED FLOORS AND BEDDING. MINI WASPS CAN BE USED WHERE SOLID MANURE GATHERS OVER A LONGER PERIOD SUCH AS IN CALF BOXES AND LARGE AREAS WITH DEEP LITTER BEDDING”

Department of Agroecology (2014)

The larvae of predatory flies eat the larvae of other flies

Predatory flies can be used to control other flies in stables because their larvae are so-called predatory larvae that feed on the larvae of other flies. They are found in the wilds of most of Europe and North America and predatory flies are neither genetically modified nor created by humans.

Predatory flies are effecient against common house flies and biting flies

Predatory flies – in Latin hydrotaea aenescens</em (also known as black dump flies, black garbage flies, and dump flies) are the natural enemies of house flies (Musca domestica) and biting flies (Stomoxys calcitrans), both of which can often be found in pig, horse and cattle stables.

 

Predatory flies are good for use in stables with slurry channels

As a rule of thumb you can say that predatory flies are really good for fly control in stables with slurry channelse. You can read more about predaty flies at How predatory flies work.

In the below video you can see how Erik Nørbjerg from Thy in Northen Jutland use both predatory flies and mini wasps with his conventional cattle herd.

 

Mini wasps lay their eggs in fly pupae and take over

Mini wasps is a small group of wasps (2-3mm.) which breed by laying eggs in the pupae of the flies leading to mini wasp larvae instead of flies.

Mini wasps are good for use in stables with deep litter bedding

As a basic mini wasps are good for stables with dry areas such as stables with deep litter bedding.

 

Place the contained of mini wasps near the area in which you want to get better fly control

Usually, it is enough to place the container with parasitic wasps near the area you to engage in fly control in – for example in a box. In other cases, it is better to spread the wasps along the edge of the box. This depends on the setup of your stable. You can read more about mini wasps on How the mini wasp .