• If you are having problems logging in please use the Contact Us in the lower right hand corner of the forum page for assistance.

fly block

Help Support Ranchers.net:


Well-known member
Mar 17, 2005
Reaction score
I am going to try some fly blocks this summer. some guys say it is a waste of money, others say it is essential... any one use them? do they work for you??
i've used them with horses; they seem to help, but the horses used them up pretty quick. also used them with a few cattle, same deal, but some of the people that run a LOT of cows will be able to help you more than i can....
I may be able to help a bit with this question, but first, do you know the ingredient that the block contains to control flies? Is it Rabon or IGR? Rabon is not nearly as effective as IGR, Rabon is bitter and it is hard to get the cattle to eat a product containing Rabon. IGR is the ingredient of choice.

We sell a lot of mineral containing IGR (Insect Growth Inhibitor). My first comment to you would be to get it in loose form, works way better than block form. Understand when you put it out that you are never going to get rid of all the flies. IGR works on horn flies. Horn flies are the flies that point downward when sitting on the cow. They are the flies that create the most economic damage. The way to tell if the fly control is working, is to see the cattle out grazing, not bunched up fighting flies. Don't go by the flies you see on the cows. The mineral needs to be put out consistently. Best not to let them run out. Aheavy fly load causes the cattle to lose a lot of fluids and also creates blood loss~all which has a very negative effect on production.

Of course, cows have to ingest the mineral in order for it to work. Our mineral (Vigortone) is designed so it will work if the cows eat only 2 oz./day. Another good thing about IGR is that it does not destroy dung beetles. Dung beetles are an important part of the eco-system as far as flies are concerned. They take care of a lot of flies. Ivomec destroys dung beetles. I have seen slides where Ivomec was used for several years and the manure build up in the pasture was terrible. The manure plots were piled up, nothing was destroying them and they were full of fly larvae. The producer switched to Safe-Guard for worming and it wasn't long until the manure piles were gone, due to the presence of the dung beetles. I think we are going to hear more about dung beetles as time goes on.

IGR works by inturrupting the life cycle of the fly. The larvae hatches prematurely, can't fly and dies. You need to start fly control when the temperature reaches 60 degrees for two to three days in a row. You should keep the fly control out until the first freeze in the fall. This helps with the hatch in the sping. More flies will die instead of overwinter, therefore, you won't see as many flies next spring.

If you have a terrible fly problem, you many need to incorporate dust bags, oilers or something else to help keep the flies down. The people here who use IGR have really seen a difference in the weight of their calves and condition on their cows. Cows have to eat to produce milk, when they are bunched up fighting flies they aren't eating~and milk production drops as a result.

Hope this helps. Feel free to ask any other questions you might have, maybe I can answer them as well. (Maybe not, too!) LOL!!
yes it is IGR and I got it in the block form so I could judge the use a bit better.....will switch to bagged when the blocks are gone. I was told that it would help reduce pink eye problems, ant that was my major goal.
Gosh, I never ever heard that IGR would reduce pink-eye problems. Pink eye can be caused from IBR and is suspect if you get an epidemic of pink eye. Face flies can irritate the eyes when they land where the eye waters and runs down the face but IGR doesn't do anything for face flies, as least as far as I am aware.

Who told you IGR would reduce pink-eye? if I may ask.

Now I am curious and I am going to check this out. Will let you know what I find out.
not sure who said it. I run Hereford cattle, and of course the pink eye problem rears its head when you sit with an Angus man.......so after a heated discussion, the bits and pieces I recalled were that feeding a fly block would reduce it.
We've started on the Right Now Mineral made by Cargill...it has IGR in it. At the seminar we went to the man said 200 flys on one cow is concidered an exceptable amount..you'll never git rid of ALL the flys..but getting them under controll helps. Before all we did was spray for flys..put em in the lot and mix up corral...in a 55 gallon barrel with a gasoline pump spray rig..yes it kills some..but it don't last long...the mineral with the fly control in it I think is the easiest way to go..plus all the other added benefits from minerals.
This is what Dr. Ranken from over at Auburn has to say about fly blosks.
[email protected]
Monday, April 11, 2005 - As we approach the summer period I am beginning to receive questions regarding the use of Rabon in the mineral as a fly control method. As most are aware this compound acts as a fly control by passing through the cow into the manure where it inhibits the development of new flies from eggs that are laid in fresh manure. It is quite effective if the cows being fed this compound are isolated from other cows. However, if cows are adjacent to neighboring cows that are not receiving Rabon then it is an exercise in futility. The flies simply crosss the fence or road and lay eggs in the manure that is present there and the life cycle continues. Thus for the system to be effective the cows must be in an isolated system or all neighboring cows must also be on the program.
there ya go JIGS! really, this is interesting to me; the blocks i've had have been RABON, and the stock have just eaten them up in NO time.

i wonder if they've had so much "sweetener" in them that that the animals have chowed down to not much effect as far as fly control...they've seemed "soft" to where the cattle/horses have just really eaten them up...

i don't have the cattle here yet, but i'll have to look into it before i buy blocks this summer.

you guys make me think, give me a headache!!! :lol:
Horn flies will only fly half mile to a host animal. If you have your cattle half mile from any others, you will see a reduction in flies. If they are closer than that, you will see more flies for a couple of weeks, then the numbers will be lower again. I think it takes two weeks for a hatch...

Alabama cattle are probably closer to the neighbors cattle than cattle in Mt. SD, ND, Wyoming, Nebraska, Kansas, Idaho, etc. so we don't see much of that problem.

Remember what I posted a long time ago about blocks? Takes a lot of licks to get one ounce of a block of something, unless it is chewable like a previous post mentioned. (Like 3,000 licks to get 1 oz. of salt)~

Dave Wieland, Independent Nutritionist ( he used to write the "consultating Nutritonist" column for BEEF magazine. I still miss his column in that publication~it was a definite asset), has this to say about fly control:

..."horn files are the most costly parasite; they cost the beef industry more than $800 million each year. It is estimated that 500 horn flies per animal will result in the loss of 1 pint to 1 quart of blood loss per day! This amount of blood loss may lead to lowered milk production, resulting in reduced weight gain in nursing calves, reduced weight gain in other classes of cattle and a lowered immune response. In addition to these losses, flies can also transmit diseases such as pinkeye, anthrax, and tb..."

"With the advent of larvacides, used either as a bolus and or as a feed additive, producers were given an exellent method of of control that acts on a completely different part of the fly's life cycle. Instead of killing the adult, larvacides, as their name implies, acts of the larva. In one group of these compounds, insect growth regulators (IGR) kills developing fly larva in the manure of treated cattle. Another class, methoprene, interrupts the horn fly's development into an adult. A convincing argument for the use of a larvacide is that there is no known resistance to these compounds. As far as effacy, larvacides should play a MAJOR PART pf a fly control program."

"The most important fact that producers need to remember is that regardless of the methods used, we will never be successful in eliminating all flies; breeding sites are too numerous, fly life cycles are short enough that reinfestation is inevitable, not all flies will be killed by any one method of control, not all producers or their neighbors in a given area practice good fly control, and the cost of such a goal would be prohibitive. Our goal should not be to eliminate all flies but should be to attempt to get fly numbers below an economic threshold, considering both the cost of control and the potential loss of production if no contol is practiced."

Hope this helps!
For fly control the only thing is a lewis cattle oiler. the mineral is not pratcial and the oiler runs for 1 dollar per head per year. All year round. Check the out on the web
How can you possibly say the mineral is not practical? Mineral pays for itself in many ways and is most certainly practical. Do you mean as a method of fly control? I just posted an informative article from an independent nutritionist about IGR. Everyone, and I say EVERYONE in this area that has used IGR in their mineral has put pounds on their calves. Now this is not to say IGR is the ONLY way to control flies.

Here is a bit more from Dave Wieland:

Fly control is a coordination game

Most cow/calf producers-about 81%, according to a 1997 report from APHIS, use some method of fly control. But only a small number have a well-managed program.

Cost, timing of control method and the inablility to implement an adequate program due to lack of facilities or cattle spread out on range are the most common reasons citied for flies not being adeqately controlled.

When setting up a fly control program for a customer, the first thing I show them is the fly number profile for the entire five to six months of the fly season. Although most producers realize that fly numbers peak in June, they don't realize there is also another peak in August, long after most control methods have been forgotten and efficacy of the insecticide used has been drastically reduced.

In recommending programs, I try to coordinate the timing of the application of fly control to be as close as possible to June to give the best results. However, branding calves and sorting cows for the range may be done earlier, and producers do not like to handle cows and calves again just for fly control. Often, this timing is not possible because cattle are on range and away from adequate facilities.

In proposing fly control programs, my first recommendation is to get an inital kill on the adult flies. If we don't knock down the adults, then the other methods will be overwhelmed and not give the desired results.

This is the major reason why most fly control methods fail. I recommend either spraying the cows or using pour-ons to achieve this initial kill. Buildings and corrals may also by sprayed to lower adult population. The
next step is to determine another method of control. I always recommend at least two different methods.


*Larvacides may be fed free-choice and may be used in most range conditions.
*Larvacides fed in this manner do not require handling of the cattle.
*Larvacides act on a different stage of the fly life cycle (acting on the larva stage rather thatn the adult fly.) No known resistance has been shown.
*I like to have mineral available for both the cows and calves

Back rubbers and dust bags are also good methods of fly control that may be used around watering places and don't require much labor or expense. Mister-sprayers or foggers may be used where cows congregrate to help reduce the adult flies. Fly tags may be used but need to be put on at the right time for best results. Be sure to use TWO tags and not just one.

Some producers think there shold be no flies on the cows. Regardless of the methods used, we will never be successful in eliminating all flies.

(There is more information about flies in the article, which I chose to skip here. Here is the concluding paragraph:)
Knocking down the adult fly population, practicing good sanitation, alternating fly tag and other insecticide types (pyrethroid or organophoshate), timing the control measures to coincide with with both peaks of the fly population (June and August) and using multiple methods of fly control should be integral parts of setting up a fly control program.

(If you wish to read the article in its entireity; see page 74 of April 2000 BEEF magazine.)

We consult with a lot of producers on fly control. There is nothing wrong with using one or more methods. Flies steal a lot of money from producers pocketbooks. I know how well the IGR works. I have old-time ranchers that use it and tell me how happy they are that their cattle are out grazing when other cattle they pass along the road are bunched up in the fence corners. One rancher that takes in yearlings sets the rule that the cattle have to be on our IGR mineral product. That is the only way he takes cattle in. That is a pretty impressive testimonial.

One of the most common problems with feeding IGR is not starting it soon enough or leaving it out long enough in the fall. If it is left out until a killing frost, it will prevent the flies from overwintering and you will not get that big hatch in the spring. Therefore, you are ahead of the game right off the bat.

If you want to gather your cattle and spray them, I suggest you wait until the breeding season is over. Do it then and do it again when you precondition your calves. We have had great experience with a product called CYLENCE. It is very easy to apply and is very reasonable as well.

In our Vigortone mineral containing IGR, it is set up so the cattle can consume 2 ozs. and still get enough IGR to control flies. We all know cattle don't eat mineral as well in the early spring and summer when the grass is green, therefore IGR is mixed in so that 2 oz. will be effective.

Vigortone does not make any product available in block form, based on their research that blocks are not an effective way of getting mineral or additives in cattle. And, as the poster mentioned above, the sweetness and softness of the block encourages over-consumption. Based on Vigortone's research, I would NEVER recommend block form.

Hope this helps!

I think he was answering in terms of the fly blocks in the original post, but your info was good,

Got my cattle all on pasture except calves and btcher cows I am feeding, feels good. Hows your spring coming?

What spring?

It is a blizzard here today! Cold, everything is froze back. 17 degrees last night, 30 degrees now. It is disgusting. It was nicer in February! Just a dry cold, some flurries when it isn't blowing the bigger flakes around. My husband is at a branding today, for pete's sake! He told the guy holding the branding, "I wish I wasn't quite such a good friend, so I wouldn't have to do this!" LOL!! Couldn't talk him out of it though. (He's Norwegian-not my husband-the guy holding the branding!)
If you are feeding a mineral with IGR and it is from a respected company you can probably get good results in block of granular form.
Now that said if pink eye is your major concern you are going after the wrong fly. Face flys spread pink eye and need other control. Vigortone has a mineral feeder that can be ordered with an optional passive wipe that gives great results and if used will help in lice control as well.
I am not saying you must use a Vigortone feeder as there are several other companies with the same design.
Remember good minerals and insect control do not cost they pay!!!

Latest posts