The horn fly is a small (one-half size of a house fly), obligate parasite. As adults, they spend most of their time on cattle, feeding on blood 30-40 times per day. The females deposit eggs in fresh manure. The life cycle consists of egg, larva, pupae and adult, and can be completed in two weeks during warm weather. The fly overwinters in the pupal form under or near manure pats. If left untreated, the population will reach several hundred per animal by mid-July.
If left untreated, horn fly numbers may reach several hundred per animal by
late July or early August. At this
level, cattle will usually bunch, fail to graze properly and expend
considerable energy in tail switching, head throwing and stamping in an attempt
to dislodge flies.
High numbers (over 200) of horn flies may reduce weaning weights, because of
reduced cow milk production, yearling weights and cow body condition scores. The degree of loss is associated with
quantity and quality of forage available and climate. Hot, dry weather and horn fly stresses seem
to be synergistic in
There are no cultural methods available to reduce horn fly numbers.
There are some predators and pupal parasites that
reduce horn fly numbers to some degree but not enough to control them. It would not be practical to rear and release
these predators or parasites.
Insecticides used for control of horn flies are administered primarily for
self-treatment by the cattle. These
would include dust bags, oilers, ear tags impregnated
with insecticides and mineral blocks or feed treated with an insecticide. Dust bags and oilers
can be either forced use or free choice.
Forced use is when cattle must pass through a gate with dust bags or oilers hung in it to obtain water, feed or mineral. Free choice is where cattle have access to
dust bags or oilers but don’t have to use them. Ear tags contain an insecticide, which moves
to the surface of the tag from ear movement and is then wiped on the haircoat of the animal, where horn flies come into contact
with it. When first used, ear tags
containing pyrethroid insecticides provided excellent
seasonal control. However, within a few
years, horn fly resistance to pyrethroids was
widespread. After resistance developed,
horn fly control recommendations returned to those made prior to the ear
tags. Animal health companies then
developed ear tags containing phosphate insecticides with no history of
resistance, boluses that contained methoprene, a
juvenile hormone, and ivermec, a broad spectrum parasiticide and newer, more toxic pyrethroids
often with a synergist added to increase toxicity or a mixture of a phosphate
and pyrethroid insecticides.
None of the newer insecticide ear tags to date have provided either the degree or length of control as the original pyrethroid-only tags. At about 60 days after application, the current ear tags start to decline in efficiency because of a reduction in the amount of insecticide released.
Sprays and pour-on insecticides will control horn flies for 2-3 weeks after application and could be used when the ear tags start to decline in efficacy. Using sprays or pour-ons for seasonal control probably is not practical for range cattle because of the difficulty in rounding up cattle for treatment. The stress of handling the cattle might offset treatment gains.
Extension entomologists developed a set of recommendations to delay or prevent the development of resistance in horn fly populations to the newer insecticides contained in ear tags. These include: 1) delay tagging animals until horn fly numbers are at an economic level (200+ per animal); 2) rotate insecticides at least yearly, a phosphate with a pyrethroid; 3) provide alternate treatment methods when ear tag efficacy declines; 4) treat only animals in a weight gain mode, i.e., cows with calves and yearlings; 5) remove ear tags at the end of the fly season.
Insecticide |
Application
Method |
Application Rate |
Restrictions and comments |
|
Coumaphos (Co-Ral) (Co-Ral Fly & Tick Spray) (Co-Ral Plus) |
Spray Spray Ear Tag |
11.6 % ELI 2.5 oz/4 gal water 6.15 % EC 2 qt/50 gal water or 5 oz/4 gal water 20 % Coumaphos + 20 % Diazinon AI
|
Restricted-Use Pesticide Do not treat animals younger than three months. Do not treat lactating dairy cattle. Spray to run-off. Treat no more than six times per year. Do not make applications less than 10 days apart. Two tags per animal. Calves less than 3 months of age should not be tagged. |
|
Beta-Cyfluthrin (CyLence Ultra) |
Ear Tag |
20 % PBO AI |
Calves less than 3 months of age should not be tagged. |
|
Cyfluthrin (CyLence) (Cutter Gold) |
Pour-on Ear tag |
4 ml/400 lb body wt. 10 % AI |
Two tags per animal. |
|
Doramectin (Dectomax) |
Pour-on |
5 mg/ml AI 1 ml/22 lb body wt. |
Do not treat lactating dairy cows or heifers over 20 months old. |
|
Diazinon (Terminator) (Optimizer) (Cutter 1) (Patriot) (Warrior) |
Ear tag Ear tag Ear tag Ear tag Ear tag |
20 % AI 20.4 % AI 40 % AI 40 % AI 40 % AI |
Two tags per animal. Two tags per animal. Two tags per animal. Two tags per animal. Two tags per animal. |
|
Eprinomectin (Eprinex) |
Pour-on |
1 ml/22 lb body wt. |
Do not treat calves under eight weeks of age. |
|
Ethion (Commando) |
Ear tag |
36 % AI |
Two tags per animal. |
|
Fenvalerate (Ectrin) |
Ear tag |
8.6 % AI |
Two tags per animal. |
|
Permethrin (Atroban Extra) (Atroban DeLice) (Atroban EC) (Boss) (Ultra Boss) (Brute) (DeLice Synergized) (Ectiban) (Insectiban) (Gardstar Plus) |
Ear tag Pour-on
Spray Pour-on Pour-on Pour-on Pour-on Spray Ear tag |
13 % PBO 1 % AI 15 ml(2 oz)/100 lb body wt. 11 % EC 1 pt/25 gal water 5 % AI 3 ml/ 100 lb body wt. 5 % Permethrin + 5 % PBO 3 ml/100 lb body wt. 10 % AI 3 ml/100 lb body wt. 1 % Permethrin + 1 % PBO 15 ml(2 oz)/100 lb body wt. 5.7 % AI 1 qt/25 gal water 10 % AI |
Two tags per animal.
Do not apply more than once every two weeks. Maximum of 5 oz per animal. Spray to thoroughly wet animal. Maximum of 30 ml per animal. Maximum of 30 ml per animal. Do not treat more than once every two weeks. Maximum of 5 oz per animal. Do not treat more than once every two weeks. Spray to thoroughly wet animal. Two tags per animal. |
|
(Gardstar) (Permectrin) (Permectrin CDS) (Permectrin) |
Spray Pour-on Pour-on Spray |
40 % EC 4 oz/25 gal water (High pressure spray) 4 oz/2.5 gal water (Low pressure spray) 1 % AI 2 oz/100 lb body wt. 7.4 % Permethrin + 7.4 % PBO 2 ml/100 lb body wt. 10 % AI 1 pt/100 gal water |
Spray to thoroughly wet animal Maximum of 5 oz per animal. Do not treat more than once every two weeks. Maximum of 20 ml per animal. Spray to thoroughly wet animal. |
|
(Permethrin) |
Dust bag |
0.25% AI dust |
Do not use in pyrethroid resistant areas. |
|
Phosmet (Del-Phos) |
Back rubber |
1 gal/50 gal water 1 gal/50 gal of fuel oil, or other suitable carrier |
Treatment-slaughter interval 3 days. Do not treat non-lactating dairy cattle within 28 days of freshening. |
|
Pirimiphos-methyl (Dominator) (Double Barrel) |
Ear tag Ear tag |
20 % AI 6.8 % Lambda-cyhalothrin + 14 % Pirimiphos methyl |
Apply two tags per animal. Apply two tags per animal. |
|
Stirofos (Rabon) (Ravap) |
Dust bag Spray
Spray Mineral additive ROL Spray |
3 % dust 24 % EC 50 % WP 4 lb/75 gal water 1.23 % AI
23 % Rabon + 5.3 % Vapona 1 qt/50 gal water |
Follow label directions. Apply 0.5 to 1 gal per animal. Follow label directions.
Do not use on dairy animals. |
|
|
Back rubber |
1 qt/25 gal of approved back rubber oil |
|
|
Zeta-cypermethrin PYthon Python (Magnesium) |
Dust bag Ear tag Ear tag |
0.075 % Dust Zetacypermethrin + 0.10 % PBO 20 % Zeta-cypermethrin + 10 % PBO (9.5 g) 10% Zeta- cypermethrin + 20% PBO (15.1 g) |
Apply two tags per animal. Apply only 1 tag per animal and do not apply Calves under 3 months of age |
The information herein is supplied with the understanding that no
discrimination is intended and that listing of commercial products, necessary
to this guide, implies no endorsement by the authors or the Extension
Services of
|
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Categories: Livestock insects, Cattle, Horn flies
Date: