Jason Smith from the University of Tennessee shares the buzz of feed-through fly control to Drovers. Treating a fly problem is not always easy- and feed-through treatments are worth considering. Feed-through fly control, where the cows consume the pesticide, have no effect on the animals themselves. They move through the digestive tract unchanged and are deposited in manure. It is here that they take effect. Two types of insecticides used in feed-through treatments: insect growth regulators (IGR) and larvicides.
Insect growth regulators are compounds that typically interfere with the progression of normal fly development. In other words, these products work through inhibiting or delaying the progression of fly larvae from one stage of development to the next. Because of this, IGR products are generally species-specific, and thus target only a single fly species. Most commonly available IGR products are only effective on horn flies. The most common of these – shown as active drug ingredient include S-methoprene.
In contrast to IGR, larvicides elicit a structural change in the fly that leads to death before it is able to reproduce. In other words, these products prevent flies from breeding. Because of this mode of action, larvicides generally are not species-specific, and thus target more than one species of fly. As a result, larvicides target not only horn flies, but also face flies and stable flies. The most common of these include Diflubenzuron and Tetrachlorvinphos.
In order to maximize the effects of feed-through fly treatments, it’s very important to make sure that they are used correctly. The products need to be given a month prior to fly emergence, and throughout the duration of the fly season.
Because these products work in a dose-dependent manner, it is imperative that cattle consume the necessary (labelled) amount of product. This means that cattle must consume the amount of feed required to deliver the necessary level of IGR or larvicide, and they must do so on a consistent basis. Take steps to ensure that these products are being consumed in a manner that will allow consistent delivery of the necessary amount of drug to manure. If using a free-choice mineral supplement as your vehicle of delivery, this requires tracking mineral consumption, and re-locating mineral feeders as necessary to achieve consistent intake of the necessary amount.
Flies can be a real nuisance to the cows and to the bottom line of farmers. Kendi E. Sayre at the University of Illinois Extension provides some great information about why it is so important to keep these pests at bay.
Each adult fly can take up 20-30 bloodmeals a day. This can result in a cow losing approximately a pint of blood a day. Flies interrupt grazing and can reduce weight gain by 17-33% over an 80-day period. This is especially seen in growing calves that have over 200 flies as their weaning weights can be up to 15 pounds lighter.
Flies that in these large populations can lead to a devastating loss of profit. Up to $68/head can be lost due to overpopulation of flies. This can also total $1 billion of income loss over the entire United States. No producer wants to lose money, let alone when there is a solution to the problem.
When is it necessary to treat fly infestations?
The economic threshold for flies on a cow are 100 flies per side for a cow, and 50 flies per side for a calf. If cows begin to have over 200 flies total (100 for calves) producers will start to see some of these negative impacts. This is when fly control programs can be so important.
Knowing the fly life-cycle and when and how they reproduce is a key component to successful treatment.
Flies lay eggs in fresh manure where they will then mature and hatch within one week. The larvae will then develop in the manure and then pupate in the drier ground underneath. They complete their entire life cycle between 10 and 20 days depending upon weather. Keep lots clean and dry inhibits the habitat needed for eggs to mature.
Feed-through fly treatments have several advantages. They are relatively inexpensive, involve very little labor, and break the life-cycle of the fly. In order for the treatment to work, you have to start treating about a month ahead of time, and the treatments are sometimes only effective on horn flies- not face flies or stable flies.
A comprehensive fly control program is recommended. Consider other fly treatment options like fly tags, oilers, pour-on, and direct sprays to supplement feed-through treatments. For more information about the different preventative methods for treating flies, as well as the advantages and disadvantages of each treatment, visit web.extension.illinois.edu.
Image Courtesy Drovers