Those Darn Flies!

Basic Fly Biology

It’s been said that every creature has its purpose. For flies their purpose is to decompose rotting organic matter such as manure, dead plants and animals. If you have an abundance of material needing decomposition, you get an abundance of flies.

Flies have four stages in their life cycle (shown in the diagram). Adult House Flies lay eggs on or close to a larval food source of rotting organic matter (i.e., manure but also compost piles, rotting hay, etc.) the eggs hatch within hours into larvae (maggots). The larvae feed and then in no less than 5 days they pupate forming a cocoon. Inside this cocoon they metamorphosis into an adult fly which takes at least 3 days.

This is the same process a caterpillar goes through as it turns into a butterfly. You can use these minimum transformation days to your advantage.

The pupa is light to dark brown and looks very much like a dark grain of rice or a rodent dropping. This is the stage the Fly Predator takes over killing that immature fly. The pupa is also the stage that flies “hibernate” when the temperature drops below 47°F allowing them to make it through the winter. Note there are no “baby” flies, when they emerge from the pupa, they are full size. The smaller flies you see are just different species.

So, it takes 345 days to produce a foal, 63 days to produce a puppy and 8 days to produce a fly!

House Fly

The easiest way to identify the flies that bug you is where they are on your animals. The most common pest fly is the non-biting House Fly. These are “filth flies” as they feed and reproduce on most any rotting organic matter, manure, spoiled feed, garbage, decaying fruit and eyes, but they can be anywhere on your animals.

Lure and capture these flies away from your barn with odor traps.

Inside the barn use non smelly sticky traps

Stable Fly

The second most common fly around horses and the most bothersome is the Stable Fly. These are blood feeders and they hurt when they cut through the skin to feed. You will find these mostly on the fore legs and flanks of horses. If your horses are stomping and twitching, it’s these bad boys (and girls).

These flies reproduce in horse manure as well as rotting vegetation. If coming from horse manure, they typically make up 20% of your fly population. If you have way more than that, then they’re also likely coming from old round bales, or old hay at the bottom of round bale rings, grass clippings, etc. that can be a mile or two away.

Put Fly Predators there or spread the old hay thinly to dry. To capture this fly you need a Biting Stable Fly Trap

When going into battle you need to have a plan of attack. If you  know who the enemy is you need to know where they live.

Are They Your Flies or The Neighbor’s?

If you are at least 1/4 mile away from neighbors with animals then it’s very likely most of your flies. If you have nearer neighbors or ones with lots of animals, then you’ll need to address those flies as well as your own. This calls for persuasion or traps. First try persuading them to use Fly Predators and maybe pickup a bit so they won’t have many flies to send you. If that isn’t going to happen, then add the right type of traps to intercept the different adult flies heading your way.

Fly Control with Horses

The first step is to identify the insect(s) that are plaguing you and your animals. With horses, the majority of your bothersome flies will likely be the House Fly (80%) and the biting Stable Fly (20%). When the fly is identified, then use the methods listed that focus on the prevention and control of that species. This is important as different flies can come from dramatically different places. Preventing flies fixes the problem. Just going after the adult flies you see only affects 15% of the population, the rest will be there bothering you in a week or so.

A key ingredient in fly control is managing your property and particularly your manure. Remember that flies breed in horse manure. You will need to clean stalls daily and compost the manure or have it hauled away frequently. Picking up manure out of paddocks and pastures will go a long way to reduce fly populations but it is labor intensive. They now manufacture pasture vacuums to make this process quicker and easier. Covering your manure pile with black plastic retains heat which kills fly and parasite larvae and stops fly access to manure.
Other steps to help reduce your fly population include raking up old hay, sealing up garbage and mowing the grass. Tall grass and weeds provide a shady rest area for flies. You certainly don’t want to have well-rested flies!

You can also put nature to work for you. Fly Predators are nature’s own enemy of all common manure and rotting organic matter breeding pest flies, including the common house fly, horn fly, biting stable fly and lesser house fly. In the natural environment Fly Predators serve as a major check of pest fly populations by destroying the next generation of flies in their immature pupa (cocoon) stage.  Fly Predators are tiny, completely biteless and stingless. They never become a pest themselves. Because of their small size and the fact they live their entire life cycle on or near manure (where the pest fly pupa are typically found), Fly Predators go virtually unnoticed.

Many people just go after adult flies buzzing around but that’s only about 15% of the population at any time. If you don’t stop the future ones you’ll be plagued all summer. Fly Predators break the fly’s life cycle. The hard working Fly Predator moms find and kill roughly 75 pest fly pupae before they hatch. Every female pest fly that doesn’t make it means potentially up to 900 fewer bothersome flies.

Using a preventive solution like Fly Predators or making the area less “fly friendly” requires that you treat the locations where the pest flies are reproducing. In almost all cases this is NOT where you see the adult flies that are bothering you or your animals. Often you will see the most flies in the barn but it’s highly likely that only a small percentage of those flies came from the barn. Instead they most likely came from the pasture, corrals, the manure pile, the neighbors animals, etc. If you’ve only been spraying, using traps, or baits you have to think differently when using prevention.

The optimum time to start for your area is when the daytime highs get into the 60s. It’s always before the flies are a problem. By starting prior to the first fly hatch there will be relatively few viable fly pupae that survived the winter so the ratio of Fly Predators to fly pupae is high. This allows the Fly Predators to reduce the initial fly breeding population to a very low level which can mean fewer flies all summer.
However, you must release enough Fly Predators to control all the fly reproduction in the area. You treat the farm not the horse. For example, if you board at a commercial stable, ordering Fly Predators for just your horse will not be sufficient as the flies that reproduce in the neighboring (within 1/4 mile) horses’ manure will easily reach your stall.