Kylie Sherrill, Livestock Technical Services Entomologist for Central Life Sciences
Filth flies can quickly impact cattle operations when left unchecked. From nuisance complaints from neighbors at feed yards to disease concerns in pastured cattle to lost milk production, there is not an aspect of the cattle industry that is left untouched by flies. For many herdsmen, fly control remains at the bottom of the lists of concerns but at a hidden cost. Filth flies such as house flies, stable flies, face flies and horn flies have been proven time and time again to be a cost cattlemen cannot afford to ignore.

First step in controlling filth flies is identifying the correct fly and understanding how they can impact your herd’s bottom line. Cattlemen with pastured herds are targeted by face and horn flies. These two species develop in fresh cattle manure and cannot stand for the manure pat to be broken up and disturbed. On the other hand, confined cattle are more likely to be impacted by house and stable flies. Both species prefer older decomposing organic matter and can flourish around spoiled feed, soiled bedding and mismanaged compost piles.

Horn flies
Horn flies are frequent blood feeders that are not found away from cattle herds. Populations begin to build in the late Spring and peak during the hottest point in the summer months. As few as 200 horn flies per cow signals the economic threshold or ET. The ET is the point where the population is causing economic loss and treatment is needed to recoup the loss. Horn fly populations can easily reach into the thousands if left untreated. It is estimated that the horn fly causes $1 billion in damages to the US Cattle Industry annually in the form of production loss and necessary control measures. Cattlemen can lose up to $40 per cow due to stress, reduced grazing and blood loss. Cattle receiving some form of fly control can increase weaning weights by 20 lbs (Campbell et al. 1976, Cocke et al. 1989). Stocker cattle on pasture can gain an additional 33lbs (Haufe 1982, Cockeet et al. 1989) if fly control is used. An Oklahoma State University Study in 2011, tested Altosid IGR, (s)-methoprene, for fly control in stocker calves with positive results. Stockers on the feed-through fly control gained over 15% more over the 86 day study period.
In addition to impacting cattle productivity, horn flies are competent vectors of Stephanofilariasis (dermatitis), and heifer mastitis. Heifer mastitis is a quiet threat that can diminish the heifer’s lifelong productivity before she even calves. Horn flies feed on the teats, transferring the bacteria that responsible for heifer mastitis, causing infection and when left untreated, can cause blind quarters and impact her productivity for life. A study in 1995 proved that 75% of retained heifers had cases of heifer mastitis. Just by implementing a fly control program, cases dropped by 55% (Nickerson et al. 1995)
Face flies
Face flies build populations in the early spring and fall but do not flourish during the summer heat. They feed on tears and other cattle secretions. Unfortunately, face flies will overwinter as adults and jumpstart the following spring’s population quickly. Face flies can influence irritation behaviors, but do not have a set economic threshold for themselves. However due to their feeding behaviors, face flies are extremely competent vectors of Thelasia (eye worm) in cattle and horses as well as IBR (infectious bovine rhinotracheitis) and IBK (infectious bovine keratoconjunctivitis – pinkeye) in cattle. It is estimated that over $150 billion is lost by the cattle industry due to pinkeye. Pinkeye impacts growth rates, with weaning weights by over 30lbs per calf (Thrift and Overfield 1974, Cobb et al. 1976, Killinger et al. 1977), as well as docked sales and treatment costs. The economic threshold for face flies with consideration to pinkeye is low, with as few as 1 or 2 infected face flies being enough to transmit the disease efficiently.
House flies
House flies are the most common pest in confinement operations. These flies may not take a blood meal but quickly impact cattle behavior and production efficiency. When stressed by house flies, cattle spend less time at the feed bunk, leading to lower feed intake, feed efficiency, gain and milk production. In dairy, it is estimated that losses of $135 million annually are attributed to the house fly. In addition, these flies are proven to carry over 200 disease causing organisms, including diseases such as BRD and BVD in cattle and several such as E. coli, Salmonella and Clostridium that impact human health. In recent years, urban encroachment into traditional livestock areas have led to several fly nuisance complaint cases against cattlemen. Unfortunately, cattlemen are not always on the winning side unless it is shown that the facility is doing all necessary steps to control house flies and their potential movement off-location.
Like face flies, the house fly economic threshold can vary by operation and other factors. To monitor house flies, “spot cards” can be deployed around the facility. The spot cards are simple index cards that are placed in areas where house flies congregate for a week at a time. If the card has 100 or more “spots” that signals a high house fly population. Cattlemen can choose to treat at a higher or lower spot level depending on disease pressure, labor or time available. Sticky traps can be used in the same fashion.
Stable flies
Stable flies are considered a seasonal pest for most to most of the United States. Populations build in early spring and decrease with the summer heat. Some regions will see a resurgence of stable flies when temperatures cool in the fall. Stable flies are a painful blood feeder and cause significant blood loss and lost productivity due to stress. Studies have shown stable flies impact feed efficiency by 12% due to the stress and avoidance behaviors of the cattle. The economic threshold for stable flies is five stable flies per the two front legs of cattle. It is estimated that stable flies cost the livestock industry over 2 billion annually. Even though we consider them a confinement pest due to their larval development needs, stable flies can become an issue in pasture settings where compost piles, hay feeding sites and feed bunks are left unmanaged.
Cattlemen should take a closer look at their fly management plans and take the time to fly control a priority. Regardless of region or industry level, leaving fly control to chance is a deficient to your herd’s health and operation’s bottom line.
This article was reprinted with permission from Central Life Sciences.