July 2006
Horses, Horses, Horses!

We have made it through one very hot June, and July is here. I appreciate the input and the emails I received from my June article on biting flies and the remedies for them. Flies are obviously pests everyone loves to hate. So much so that I have had a request to write another article on flies… this time on the bot fly. Now of course I know you are practically chomping at the bit to hear more about this "wonderful" pest.

The bot fly, otherwise known by its three varieties: horse bot fly (gasterophilus intestinalis), Nose bot fly (gasterophius haemorrhoidalis) and the Throat bot fly (gasterophilus nasalis). "Lovely, lovely, lovely" creatures they are indeed. Each species of this creature has its own distinct way of entering the horse, thus the three names.

The horse bot is probably the species most people recognize in the egg stage of the fly’s life cycle. They are the yellow "dots" that are attached to the mane and/or legs (usually both) of the host horse. Most every horse person has seen these at one time or another. Unfortunately, horses are the natural host for this pest and bots are found generally everywhere horses reside. The good news is that nowadays these pests are not nearly as big of a problem as in bygone days because of better deworming programs and practices and more efficient wormers.

The life cycle of the bot fly is very similar for all three species; it is just that each has their own venue for getting inside the horse. Whereas the horse bot lays its eggs on the mane and legs of the horse, the nose bot lays its black eggs on the fine hairs of the lips, and the throat bot lays its eggs under the chin. As horses groom themselves and each other, they ingest the eggs. The body temperature of the horse’s mouth and throat cause the eggs to hatch, and the newly hatched larvae travel down to the stomach to live happily for several months.

Herein is where the trouble starts for the horse. The damage that the larvae (also known as "worms") can do to the inside of a horse is cause for making sure your horses are dewormed on a regular schedule. The larvae can cause stomach lesions that get infected, interfere with food passage and "run down" the horse. Once the larvae are ready, they will pass with the horse’s droppings and pupate beneath the soil. Adult bot flies will emerge from the pupae in the early summer.

Adult bots are furry-looking and bee-like in appearance, and are relatively harmless because they do not feed at all. They mate and, of course, lay eggs that in turn produce the larvae that are so harmful. The whole process of the life cycle from egg to larvae to pupa to adult takes one year to complete and starts all over again unless dewormers are introduced into the horses system to rid the horse of the larvae.

Dr. Jason Coe of the Oneonta Animal Hospital said that it is recommended to use a dewormer with ivermectin in it every other month to kill the bot larvae and prevent the bot flies from completing their life cycle. Dr. Coe, like many, has seen the effect and benefits of using ivermectin to combat bots and believes ivermectin products being used in regular deworming programs are the very reason that bots are no longer the problem they used to be.

This is good news for horses and their owners. Even more good news is that ivermectin products are readily available at your local Co-op. There is one newer product called Zimecterin Gold by Merial that kills bots and many other equine parasites, including tapeworms. You can check with your local Co-op to find out about this product. As always it is wise to check with your veterinarian about any program you use for your horse’s health; and always, always, always read and follow the directions on any products you buy.

As I close I would like to say thank you to those of you who email in to comment about the monthly articles I am doing. It is very encouraging to hear good things and to know that the information being provided is helpful. An email was received from Harriette Dye of Vestavia Hills in response to the June article’s discussion on "homemade fly spray." Harriette wrote:

Enjoyed your June article on fly control. I have in my recipe box a concoction for fly spray that I have no idea where it originated. It is:

3 oz. Avon Skin So Soft
3 oz. Citronella oil
12 oz. White vinegar
12 oz. Water

I must admit I never tried this. It is just too easy to pick up a bottle of fly spray from the Co-op.


Thank you Harriette for the wonderful email and for sharing your recipe. I know that it will be appreciated by those who are seeking homemade recipes.

Once again I would really like to know what horse people want and need to know about their animals. Please feel free to send suggestions, questions and/or comments to the mailing address: Cooperative Farming News, P.O. Box 2227, Decatur, AL 35609-2227 or fax 256-560-2605 or email This email address is being protected from spambots. You need JavaScript enabled to view it..

Janet Bryant is a freelance writer from Oneonta.

Editor’s Note: The publication of the homemade fly spray recipe contained in this article is not an endorsement by AFC or any of the Co-ops. It has not been tried by any of our personnel and should be used at the discretion of the reader.