The Use of IVOMEC® (ivermectin) Pour-On and Permethrin Ear Tags for Season-long Ho. Page 1 of 4
The Use of IVOMEC® (ivermectin) Pour-On and
Permethrin Ear Tags for Season-long Horn Fly Control
James A. Hawkins, DVM, PhD
Hawkins JA, Foil L, Strother GR. Season long horn fly control using IVOMEC®
The Horn Fly
(ivermectin) Pour-On for cattle and pyrethroids ear tags. Proc AAVP 41st Meeting,
Benefits of Horn Fly Control
The horn fly is a major pest of cattle. Drummond et al
Use of IVOMEC®
estimated annual losses from horn flies for cattle production in the United
States of $730 million. They have also reported that horn flies cause an On In A Strategic
estimated weight loss of 12 lb. per calf, 10 lb. per head of stocker cattle,
Horn Fly Control
4.6% weight loss of slaughter cattle as well as a 1% reduction in milk flow
Program in the
during the 6-month horn fly season. Accepted estimates of the economic
threshold of horn flies on cattle range from 50 to 200 flies per animal,
Extensive data are available to document the efficacy and duration of
internal and external parasite control with IVOMEC Pour-on following a single treatment. Effective control of horn flies for the duration of the
season, however, often requires several treatments, and may also require
several different products. These trials demonstrate the benefit of using IVOMEC Pour-On in conjunction with permethrin ear tags in a strategic
program to obtain season-long control.
The Bottom Line
Recommendations for the use of IVOMEC Pour-On generally suggest the
use of other commonly used horn fly control products in conjunction with
IVOMEC Pour-On in order to obtain season long control. Two studies were
conducted in Louisiana in 1994 and in Alabama in 1995. The objective was
to evaluate the efficacy of a spring and mid-summer application of
IVOMEC Pour-On in conjunction with a spring application of permethrin
ear tags as a program for season-long control of horn flies. The results of treatment of cattle with IVOMEC Pour-On for parasite control in these
The Use of IVOMEC® (ivermectin) Pour-On and Permethrin Ear Tags for Season-long Ho. Page 2 of 4
! Spring application of IVOMEC Pour-On alone resulted in significantly
fewer horn flies compared to untreated controls and fly numbers
below the economic threshold of 100 flies per side - P<0.05 through
week 5 in 1994, and P<0.01 through week 8 in 1995.
! Spring application of IVOMEC Pour-On in conjunction with permethrin
ear tags resulted in significantly fewer horn flies compared to
untreated controls and fly numbers below the economic threshold of
100 flies per side - P<0.05 up through week 5, 7, 9 and 11 in 1994 in,
and P<0.01 through week 11 in 1995.
Merial. 1998 Merial Limited. All rights
! An additional mid-summer application of IVOMEC Pour-On, with or
without application of ear tags in the spring, resulted in significantly
fewer horn flies compared to untreated controls and fly numbers
below the economic threshold of 100 flies per side - P<0.05 an
additional 4 weeks post-treatment in 1994 in, and P<0.01 an additional
5 weeks post-treatment in 1995.
The Field Trials
These trials were performed in Louisiana in 1994 in cooperation with
Louisiana State University, and in Alabama in 1995 in cooperation with
Auburn University. Both trials were conducted under the same protocol. All
cattle were spring calving commercial cross-bred beef cattle with the
exception of one herd which was purebred Angus. Each trial utilized 4
separate cow/calf groups on each of 4 different farms. Each group was
separated from all other cows by a minimum of 1000 feet to minimize horn
fly movement between treatments or into treatment groups from
surrounding herds. All non-test cattle on each farm were treated for horn
flies in an identical manner to equalize horn fly numbers on the farm. All
management practices were identical for each treatment group on each
farm, with the exception of the test treatment.
Each treatment group consisted of a minimum of 20 cows and their calves. The groups received the following treatments:
Group 1: Control - No treatment for horn flies.
Group 2: Ear Tags only - Spring application of ear tags.
Group 3: IVOMEC Pour-On only - Spring and mid-summer application.
Group 4: IVOMEC Pour-On plus Tags - Spring and mid-summer application of IVOMEC Pour-On plus ear tags in the spring only.
All cattle designated to receive ear tags received two (2) permethrin insecticidal ear tags (one in each ear) in the spring if they were 6 months of age or older. Ear tags were removed at the mid-summer treatment for cattle of Group 4.
Horn fly counts were made weekly by counting horn flies on 1 side of 10 or
The Use of IVOMEC® (ivermectin) Pour-On and Permethrin Ear Tags for Season-long Ho. Page 3 of 4
12 cows in each treatment group. The same cows were used for fly counts each week from each group. All fly counts were made before 8:30 am. Adequate horn fly control is considered to be the economic threshold of less than 200 flies per cow (less than 100 flies per side). Results from each study are presented in Figures 1 and 2.
Treatment with ear tags alone provided 4 to 8 weeks of adequate horn fly
control (1994 and 1995 respectively). Treatment with IVOMEC Pour-On
alone provided 5 to 8 weeks of control. Treatment with IVOMEC Pour-On
in the spring in conjunction with ear tags provided control through week 11
in both years.
Treatment with ear tags alone (applied in the spring) provided no additional
control at the time of the mid-summer treatment or thereafter, compared to
the untreated control . An additional mid-summer treatment of IVOMEC
Pour-On applied to cattle in both Groups 3 and 4 provided 5 more weeks of
control in addition to that resulting from the spring treatment.
Figure 1. Average Horn Flies Per Side - Louisiana 1994
Figure 2. Average Horn Flies Per Side - Alabama 1995
The Use of IVOMEC® (ivermectin) Pour-On and Permethrin Ear Tags for Season-long Ho. Page 4 of 4
Recommendations for use of IVOMEC Pour-On generally suggest the use of other commonly used horn fly control products in conjunction with IVOMEC Pour-On in order to obtain season-long control. Data from these trials indicate that treatment with IVOMEC Pour-On for parasite control in the spring and mid-summer, in conjunction with application of permethrin ear tags in the spring provided better and longer lasting horn fly control than either product alone.
Veterinary Professional Services, Merial Limited,
2100 Ronson Road, Iselin, NJ 08830-3077. Tel 1 888 637 4251
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