Submitted by: Dr. Chandlar Kern, Penn State Extension Livestock Educator
Summer brings longer days, abundant forage, and growing calves, but it also brings one of the most frustrating challenges for beef producers: flies. Heavy fly pressure can reduce grazing time, lower weight gains, and increase stress, making flies more than just a summertime nuisance. Beyond their direct impact on cattle performance, flies can also play a major role in the spread of pinkeye, making fly control an important part of summer herd management. Several species of flies affect beef cattle, but face flies are among the most concerning because of their connection to pinkeye. Face flies feed on secretions around the eyes and nose of cattle and can move bacteria from infected animals to healthy animals. As face fly populations increase during the summer months, so does the risk of pinkeye outbreaks.
Pinkeye, or infectious bovine keratoconjunctivitis (IBK), is one of the most common eye diseases in beef cattle. Early signs include excessive tearing, squinting, sensitivity to sunlight, and inflammation around the eye. As the disease progresses, a white spot or ulcer may develop on the cornea. Severe cases can result in blindness, reduced weight gain, and increased treatment costs.
Fortunately, there are several management practices that can help reduce the risk of both flies and pinkeye. No single fly control method works perfectly on its own. The most effective programs use multiple strategies throughout the fly season. Insecticide ear tags remain a popular option for pasture-based beef operations. Tags can help reduce fly numbers, but producers should follow label directions carefully, rotate insecticide classes from year to year, and remove tags at the end of the season to help reduce insecticide resistance. Dust bags, back rubbers, oilers, sprays, and pour-on products can also be effective, particularly when positioned where cattle are forced to use them, such as near water sources, mineral feeders, or pasture gates. Control methods that target the animal’s head and face are especially valuable for reducing face fly populations. Feed-through insect growth regulators (IGRs) are another tool that can help reduce fly development in manure when consumed consistently throughout the fly season. These products are most effective when the entire herd has access and consumption is adequate.
While developing a summer fly control program, producers may also want to consider products that provide both fly and tick control. Tick populations continue to expand across Pennsylvania, and the spread of the Asian longhorned tick has increased concerns about Theileria orientalis Ikeda, a blood parasite that can cause severe anemia, weakness, abortions, and death in cattle. Although no single product should be relied upon as the sole means of tick control, selecting fly control products with labeled activity against ticks may provide additional value as part of an integrated parasite management program. Producers should consult product labels and work with their veterinarian or Extension educator to determine which options fit their operation and management system.
Pinkeye often develops when the eye becomes irritated and susceptible to infection. Tall grasses, weeds, seed heads, dust, and ultraviolet (UV) light can all contribute to eye irritation. Maintaining pastures through clipping or rotational grazing can help reduce seed heads and tall vegetation that may scratch cattle’s eyes. Managing dusty conditions around feeding areas and heavy traffic locations can also reduce irritation. Providing access to shade may offer additional relief during periods of intense sunlight and heat.
Even with good prevention efforts, some pinkeye cases may still occur. Early detection is critical. Producers should watch for cattle with watery eyes, excessive blinking, squinting, or signs of discomfort. Animals showing early symptoms should be evaluated promptly. Many producers wait until the eye becomes cloudy or severely damaged before initiating treatment. However, treatment is generally more successful when cases are identified early. Work closely with your veterinarian to develop a treatment plan and discuss whether vaccination may be appropriate for your operation.
Successful fly control is not a one-time treatment. It requires consistency throughout the summer. Treating only a portion of the herd often allows flies to continue reproducing and spreading throughout the operation. Likewise, relying on a single control method may not provide adequate protection during periods of heavy fly pressure. Combining multiple fly control methods with good pasture management and prompt treatment of pinkeye cases can help reduce economic losses while improving cattle comfort and performance throughout the grazing season. As summer progresses, now is a good time to evaluate your fly control program and make adjustments if needed. A proactive approach can improve cattle comfort, support performance, and help keep pinkeye from becoming a costly problem in the herd.
