Controlling External Parasites In Beef Cattle
In order for anyone to maintain the comprehensive health of a herd of beef cattle it is
necessary to plan and follow a systematic program of external parasite control. Each year the US cattle industry
loses hundreds of millions of dollars because of the destructive effects of parasites. Flies, ticks, mites, grubs
and lice are all part of this national problem.
Cattle owners lose money in many different ways but primarily
parasites create loss through
• Reduction of animal performance
• Decreased milk production and ability
• Decreased fertility
• Loss of market value
External Parasites- Control Program for Beef Cattle
External parasites of beef cattle can be controlled by using a wide variety of products:
• ear tags
• Wet applications or pour-on insecticides
• back rubbers
• Mineral additives
Ear tags that contain organophosphate or man made pyrethroids are easy ways to use insecticides
that can control flies and ticks. These have been used for almost 30 years but some cattle owners have had varying
results due to misuse. When ear tags were first used the flies would be off the animal in 15 minutes. However these
ear tags have been overused and this has led to resistance among the fly population on many of the farms. Here are
the proper directions that should be used with ear tags or “fly tags”.
• Use two tags, one in each ear for every animal
• Tag the calves
• Use the ear tags beginning around the 15th of May, if they are used too early the medication will
run out before fly season is over
• Remove the ear tags in the fall around October 1st
• Rotate the types of ear tags you use every year so you do not use the same insecticide compounds
continually. If you are using ear tags with an organophosphate compound this year you should switch to tags with a
man-made pyrethroid compound next year.
External Parasite Application Treatments
Some people will choose specific parasite treatments that need to be applied to the animal’s body.
These can be very effective but must be used correctly.
• Only apply these medications or insecticides on a day when rain is not forecast. If it rains during the first 4
hours after you applied the treatment then the water will render it useless.
• Sprays and pour on applications for external parasites can be used but directions must be
followed carefully and contamination of food and water should be avoided. Always use a glove, safety goggles and
mask when applying any dust or liquid medication to animals.
• Backrubbers and facerubbers can be used for control of lice and most of the biting insects. These
must be kept charged and daily use will provide the best results. Only use#2 diesel grade oil or approved
backrubber base oil.
• Dust bags can be used with good results but must be hung where cows will come in contact with
them. Protect the dust bags from rainy weather to prolong their use. If you choose a hand dusting method for
applying insecticides to cattle you need to make sure that you contact the skin under the hair.
Important Reminders Regarding External Parasite Treatment and Control for Cattle
• Sprays for Grub control should only be used between August 1 and November 1. If used after this
time the larva can be in vital areas of the cow’s system and the spray can result in bloat, paralysis or death of
• Fly control should be started in mid-March or no later than mid-April.
• There is no internal or external parasite treatment that lasts for 6 months.
• Internal and external parasite treatments for beef cattle will be effective for 1-2 months
• Treat cattle for grub and lice in the early fall and again in January or in February.
• Check with your veterinarian to determine the best parasite control system to use for the needs
of your herd.