Horn and face fly numbers can continue to build throughout the summer, which will put pressure on your control programs.
Now is a good time to evaluate the pasture fly situation in your herd. Check during the early afternoon on a sunny day.
Less than 100 horn flies per side and less than 10 face flies per head is a good target for animal protection. Consider an adjustment or supplemental measure if fly numbers exceed these guidelines.
Late-season fly control is important. Pasture flies are approaching peak numbers for the season, so their impacts are near maximum levels.
Also, exposing flies to less than the recommended rates of insecticide, due to less effective treatment, selects for resistant individuals and increases the chance for control failure. To ensure flies are kept in check, use an integrated approach. The following suggestions will help:
Insecticide-impregnated cattle ear tags can provide 12 to 15 weeks of protection. Effectiveness may be running out in herds that were tagged early in the season.
Feed-through insecticides in mineral supplements require a minimum level of daily consumption by each animal. Be sure that the product is available and that the consumption rate appears to be on-target. This alternative is based on controlling horn and face fly maggots that develop only in cow manure.
Face and horn flies can move a mile or two, so action may be needed to control flies that move in from nearby herds. Provide supplemental control, as necessary.
Self-applicators, such as dust bags, backrubbers and oilers, are effective, but be sure they are charged and working. In some cases, enough dust can build up to reduce the wicking action in wipes and oilers.
Be sure dust bags have not been damaged and that the insecticide in them is dry and flowing.
Pour-on and spray applications generally provide no more than four weeks of fly control. Check the last treatment date, and be sure doses are measured accurately.
If you do apply a spray or pour-on to supplement the declining effectiveness of another product, use a product containing an active ingredient with a different mode of action from the product you used earlier in the season.
For example, if you used an organophosphate ear tag (such as Corathon®), use a pyrethroid pour-on or spray (such as CyLence®) for supplemental control.