Producers today have a larger arsenal of products available to combat horn flies and face flies compared to 15 years ago.
These insects can cause considerable livestock weight loss and irritation issues.
Horn flies are the ones we see on cattle’s backs in summer. They bite through the hide 20 to 40 times daily and draw blood. This makes quiet cattle nervous, which leads to lower milk production, and that can reduce calf weaning weights by as much as 14 percent. The calves get a double whammy — less milk plus fly bites and irritation.
Face flies feed on animal secretions, such as eye discharge, and can be so bothersome to cattle that they graze one hour less per day. That leads to less weight gain. As well, face flies can spread diseases such as pinkeye.
The life cycle of both flies involves eggs being laid in cattle manure. Their entire life cycle lasts two to three weeks, which means there can be up to five life cycles through the summer in our northern climates. More than 50 face flies per animal are significant.
Several options exist including insecticide ear tags that have been around since the 1980s, pour-on macrocyclic lactones (ivermectin type products like Solmectin or Ivomec) and pour-on pyrethroid products like Saber, Boss or Cylence.
Several years after the fly tags came out, resistance started to develop so different chemical compounds were developed.
Now, we can watch for the reoccurrence of flies. These products should give almost 100 percent protection from flies for the first few weeks.
If this is not the case, resistance may be developing and a switch to a different product may be necessary. There are also fly control products given by cattle oilers mixed with mineral oil or canola oil.
The cattle oiler options have been reduced lately with the removal of Malathion and I would recommend producers avoid mixing with diesel fuel if using cattle oilers.
The cattle oiler product available in Canada is a permethrin insecticide. One of the trade names is Ectiban but there are others and with insecticides we need to follow the label.
Oilers can provide continual treatment for flies, and lice and mosquitoes are indicated as well. A disadvantage is that oilers require a large capital outlay and yearly maintenance. There is a one day withdrawal time from an oiler before shipping cattle to slaughter.
The macrocyclic lactones (primarily the ivermectins) are the pour-on products most of us are familiar with.
They are still highly effective against lice and warbles but the effectiveness is waning against internal worms and many producers or veterinarians don’t think of them as a fly treatment even though they could be.
They are on label for fly control for 35 days and because the product goes systemic and is excreted in the manure, the fly larvae will be killed. Killing the larvae is a big benefit before they become flies.
These products have a longer slaughter withdrawal (49 days for most) but the ivermectin products have come down greatly in price over the years so are economical to use.
The broad spectrum of activity with an easy way to apply make these types of products advantageous.
The pour-on pyrethroids are the next category of insecticides producers and veterinarians can use for fly control.
These products generally work for both flies and lice. Some have efficacy for certain ticks as well. They require a small volume of material poured over the back. The products I am most familiar with are Saber, Boss and Cylence.
All of them work about the same way and control lice biting and sucking, as well as have a few weeks duration for effective fly control. Withdrawal times range up to a week but slaughter dates rarely come into play on pasture cattle.
The fly tags available on the market have a longer duration at about three months but are limited to fly control. Longer duration leads to higher cost and more labour to take old tags out and put in the new ones.
With point-in-time treatments, the closer a producer can treat to the actual fly season, the greater the benefit.
Any time a producer is running cattle through the chute in later spring or during summer, fly control should be on the to-do list.
With multipurpose products, weight gains are generally cumulative with flies, lice, internal parasites and in some cases ticks, all adding to decreased gains.
By breaking the fly cycle and killing adults early, we reduce the fly level for the entire season.
In our neck of the woods, July and August are the worst times for flies. Ask your veterinarian about recommending good fly control products. Apply it properly at the right dosage and reap the benefits of good quality fly control for your entire herd.