Fly Fighting

Written by Dr. Jim White on .

Flies cause substantial economical losses to cattle producers; e.g., biting flies carry diseases such as anaplasmosis and bovine leukosis virus. Face flies can spread pinkeye from animal to animal. Flies are well adapted to the environment. They have been around for thousands of years and are doing very well for themselves. The adaptability of flies means that it is going to be impossible to completely remove them from your operation. However, there are ways to control flies and to lessen their negative impact.

1. FEED AN INSECT GROWTH REGULATOR. These are either Altosid to treat horn flies on pastured cattle, or Clarifly for confinement cattle. Clarifly has a claim for face flies in addition to horn flies. Clarifly costs about twice as much to use compared to Altosid, but it gets twice the fly species. The pesticide should be fed starting 30 days before flies typically appear, and should be continued for 30 days after a killing frost. This roughly means feeding it between March 15 to Nov. 15. While horn flies don’t travel far, face flies will travel up to two miles.

2. USE FLY TAGS. Newer-generation fly tags are quite useful in controlling fly populations. To reduce pyrethroid resistance, after using pyrethroid tags for two consecutive years, switch to an organo-phosphate tag for one year. For optimal fly control, many products require two tags for an adult animal and one tag for a calf. As always, whenever you are using a pesticide follow the label directions. Applying the tags too early will be result in less effective fly control. The ideal time to apply tags is when there are about 200 horn flies per cow. The best time to check this is in the early morning hours: it is cooler, and the wind tends to be down. Look at the animals as they graze, it is relatively easy to see the flies on their sides.

3. USE POUR-ONS. You can apply a pour-on at the same time you flytag your cattle. If you are doing this during spring turnout time, you can use a product that kills internal parasites, these products are also effective against flies. If you do this later in the year, use products that are just labeled for flies and/or lice.

4. PROVIDE DUST BAGS/CATTLE RUBS. If you place a dust bag or rub at a site where all cattle use it, and keep it charged with insecticide, it can provide a very economical means of controlling face and horn flies.

5. SPRAY CATTLE. If you use a spray product on your cattle at timely intervals it can be very effective at reducing the fly population. Though useful, this method can be time-consuming.

When working on controlling flies and lessening their damage to your cattle, it is unlikely that one strategy alone will be sufficient. When you use several methods in conjunction, you are better able to lessen the negative impact of flies. If grass tetany is a concern, use Mag- Ade Meal IGR-CTC. If you offer free-choice mineral and want to minimize problems, feed Ricochet FESQ Max CTC-Alt. If you need a fescue equalizer, feed Fescue Equalizer CTC-Alt.

Horn flies cost the American cattle industry a couple of million dollars every day. Horn flies are about half the length of a house fly. Both males and females are blood feeders and congregate on the shoulders and backs of cattle. When disturbed, horn flies will fly up in a swarm, but they will return to animals almost immediately. Females leave occasionally to lay their eggs in fresh manure piles.

The close association between horn flies and host helps with control. The flies leave animals only to lay eggs or to change hosts. Thus many methods will expose flies to control practices (ear tags, topical products, feed-through feed additives). With some chemistries (pyrethroids), insect resistance has been an issue. Resistance is not a problem when using IGR-insect growth regulator, chemical name S-methoprene; there is no known resistance to IGR-methoprene-Altosid. The appropriate application of an IGR feed-through product is that the horn fly control is long-term and preventive, not reactive. IGR is ingested as part of the animal’s feed. Cattle then excrete manure which has IGR. Given that horn flies must lay their eggs in fresh manure, the IGR is there to keep the horn fly pupae from developing into breeding, biting adult horn flies.

Ricochet FESQ Max CTC-Alt is a convenient, ready-to-use mineral formulated to balance range or pasture feeding programs for beef cattle. The inclusion of IGR and CTC allows for both horn fly control and medicated feed claims.

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