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Horse and Deer Flies (Tabanidae spp.)
This year, there has been a noticeable increase in deer and horse fly populations. These flies inflict painful bites on mammals, including livestock and humans.
Female horse and deer flies possess sharp mouthparts that they use to cut through the skin of their hosts, lapping up the blood that flows from the wound. This biting behavior causes significant distress to livestock, especially when fly populations are high.
Photo By: Ward Strong, BC Ministry of Forests, Bugwood.org
Photo by: Sturgis McKeever, Georgia Southern University, Bugwood.org
Horse and deer flies are commonly found near tree lines and wet areas, as they thrive in aquatic and semi-aquatic habitats during their egg and larval stages. Most species prefer environments such as streams, ponds, or swamps, though some are found in wooded areas with abundant leaf litter. The development time from egg to adult varies widely among species, ranging from 90 days to several years.
Life Cycle
Horse and deer flies lay between 100 and 800 eggs on vegetation above wet areas. Upon hatching, the larvae drop into the water or moist ground below. Depending on the species, the larval stage includes 6 to 13 instars before pupation. These insects typically overwinter in the pupal stage.
Control Measures
Managing horse and deer fly populations on cattle is challenging due to the flies’ quick feeding habits. They land, cut open a spot, and take a blood meal rapidly, reducing their exposure to control measures. These flies often concentrate in specific areas on a farm.
For farms experiencing significant fly populations, various traps can be used to manage their numbers, including the Horse Pal, H-Trap, and Epps Trap. These traps have been found to be effective in certain situations. Placing traps in areas where flies are most prevalent can help reduce their numbers locally. It is essential to position the traps out in the open but away from cattle, as the animals may damage them.
By strategically placing traps and managing habitats, farmers can alleviate some of the issues caused by horse and deer flies, improving the well-being of their livestock and reducing the nuisance to humans.
Stable Flies
Stable flies (Stomoxys calcitrans), known for their painful bites using piercing mouthparts, require blood to reproduce. This causes significant discomfort to cattle and, when populations are high, can reduce milk production in dairy cows, weight gains in calves and beef cattle. Both female and male stable flies feed on blood once or twice a day, typically targeting the legs of the cattle. However, when populations are high, they will feed on other parts of the animal as well.
Cattle under attack from large numbers of stable flies often show signs of distress, such as vigorously stomping their legs to dislodge the flies, which further impacts their feeding time, weight gains and milk production. Stable flies can infest cattle in both barns and pastures.
This video shows cattle moderately stomping off stable flies
Stable flies deposit their eggs in decomposing organic material and thrive in environments containing rotting moist grass, hay, straw, manure, and silage. They also lay eggs in lake weeds accumulating on banks, and any other decomposing materials leading to significant infestations, and can migrate long distances to find livestock.
A single female stable fly can lay up to 400 eggs and survive for about a month. Under optimal warm conditions, their lifecycle spans approximately 21 days from egg to adult. Once emerging as adults, they can take a blood meal within 12 hours.
Action Threshold
The action threshold for stable flies is a cumulative count of 10 flies on all four legs of an animal. Observing and counting flies on at least 10 to 15 cattle, then calculating the average, helps determine if intervention is necessary.
Management of Stable Flies
Sanitation: Proper sanitation is crucial for controlling stable flies. They lay eggs in moist, decaying organic matter. Breaking their lifecycle by regular cleaning is essential. Clean all moist organic matter from every corner of the barn, including stalls, calf hutches, pens, maternity areas, sick cow pens, under feeders, manure handling areas, and storage areas for feed, silage, and hay. Even a small amount of moist organic matter can produce hundreds of flies.
Composting: Composting manure, feed, old silage, hay, and bedding materials can kill fly eggs, maggots, and pupae. Compost piles reaching 120 degrees or more can effectively eliminate these stages of the fly. Turning the compost pile weekly prevents reinfestation by flies.
Spreading Manure and Bedding: Spreading manure, old bedding, silage, hay, and feed on a field in a thin layer allows the material to dry out, killing fly eggs and maggots in the decomposing organic matter.
Bedding Types: The type of bedding used can impact fly control. Moist straw mixed with manure, silage, hay, and feed is ideal for fly reproduction. Alternatives like sand, gravel, wood shavings, wood chips, and sawdust have lower fly reproduction rates. Nonetheless, regular cleaning of manure, feed, silage, and hay from stalls and pens is necessary.
Placement of Feed and Water: Placing feed and water outside of calf hutches, pens, and free-stall areas prevents contamination of bedding, reducing the risk of flies laying eggs.
Water Control: Preventing water from contacting bedding, hay, or feed is essential. Position waterers to avoid spillage, ensure proper drainage around barns, and direct rainwater away from buildings and feed storage areas. For calf hutches, mound gravel to ensure proper drainage and prevent moisture build-up. Adequate ventilation and dry conditions in calf hutches are also crucial.
Bedded Packs: For producers using bedded packs, it is essential to keep the area dry and add fresh bedding material regularly. Properly maintained bedded packs can minimize fly production.
Clean Hay/Haylage Feeders on Pastures: Stable flies breed in areas where hay or haylage accumulates on pasture. Clean these areas weekly to prevent significant fly production.
Biocontrol: One type of natural predator of fly pests is parasitoid wasps, which may already be present on farms. To enhance their impact, additional parasitoids can be purchased and released. By strategically releasing specific parasitoids in barn areas, the wasps act like “smart bombs” and target stable fly pupae.
For comprehensive insights into parasitoids targeting house and stable flies, please explore the following website: https://cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/fact-sheets/muscidifurax-raptor-and-m-raptorellus-biocontrol-agent-fact-sheet
Organic Solutions
For organic producers, approved forms of pyrethrum or neem and other natural repellents can offer some relief, though their efficacy may be limited to short durations.
Insecticidal Measures
Residual insecticides can be applied to barn walls to control stable fly populations. Flies resting on treated surfaces will be exposed to the insecticide. Various insecticidal products can also be applied directly to cattle to reduce fly pressure. VetPestX is a valuable resource for selecting suitable insecticides tailored to specific pasture conditions. More information can be found at VetPestX.
Horn fly populations are increasing rapidly this year, with some beef cattle exceeding the 200-fly action threshold. These flies cause significant pain and annoyance to dairy and beef cattle, leading to economic losses due to reduced milk production in dairy cattle and decreased weight gain in beef cattle.
Photo by: Craig Sheppard, University of Georgia, Bugwood.org
Horn flies are biting insects that need a blood meal from cattle to reproduce, with both females and males consuming up to 30 meals daily. They are smaller, about half the size of face flies or stable flies, and primarily infest the back and sides of cattle, moving to the belly in higher temperatures. Horn flies spend most of their lives on cattle, leaving only to lay eggs in fresh manure. Each female can lay up to 20 eggs at a time, totaling around 400 in her lifetime. Maggots in manure can reach high populations.
The horn fly life cycle spans 10 to 20 days, with adults living about a month. They develop only in cattle manure pat on pasture, not in manure from other livestock. In the northeastern United States, there are typically 12 to 14 generations per grazing season.
To determine if control measures are needed, scout the cattle on pasture. Take photos of the cattle where the flies are, count the flies in that area, and estimate the number of horn flies on one side of the cattle. Depending on herd size, count up to 15 cattle, take the average, and compare it to the action thresholds.
Action Thresholds
- Dairy Cattle: 50 horn flies per shoulder, side, and belly.
- Beef Cattle: 100 horn flies per shoulder, side, and belly.
Control Methods
Bruce Trap (Passive Walk-Through Trap)
Horn flies, which dislike enclosed spaces, fly off the cattle as they enter the trap. The trap features strips of old carpet or canvas that brush off the flies, which then move towards the light and are trapped by double screen walls. Data suggests that this trap can control 50 to 70 percent of horn flies over time.
CowVac
The CowVac is an advanced vacuum system designed to remove horn flies from cattle. It generates a strong air current that dislodges flies from the cattle’s body, while a high-powered vacuum sucks up the dislodged flies. This trap has been shown to reduce horn fly populations on farms by 68%, improving cattle health and comfort and reducing the need for chemical treatments.
Flatten Manure Pats
Disrupting breeding habitats by flattening manure pats on pasture can control horn flies. Dragging a harrow or chain over the pasture spreads out fresh manure, causing it to dry out and preventing egg and larvae development. This method is particularly effective in rotational grazing systems but can be labor-intensive.
Shaded Areas
Providing shaded areas, such as sheds or barns, allows cattle to escape flies. Darkened spaces can significantly relieve cattle from the stress and annoyance caused by flies.
Organic Solutions
For organic producers, approved forms of pyrethrum or neem and other natural repellents can offer some relief, though their efficacy may be limited to short durations.
Insecticidal Measures
When infestations are significant, insecticides may be necessary. Use them only when populations exceed the action threshold. Methods include sprays, pour-on, ear tags, back rubbers, and dust bags, targeting areas where face flies congregate.
VetPestX is a valuable resource for selecting suitable insecticides tailored to specific pasture conditions, aiding producers in making informed choices. More information can be found at VetPestX.
Face Flies Already!
Yesterday, amidst our routine fly counts on beef cattle, we encountered a concerning influx of face flies. This year, their presence seems particularly pronounced, with some unfortunate animals bearing as many as 70 of these bothersome insects. Such numbers far surpass the accepted threshold of 10 flies per animal, prompting a heightened awareness of the potential issues they pose.
Resembling common house flies, female face flies predominantly target areas around the eyes and nose of cattle, as well as any wounds or cuts. Feeding on animal secretions, flower nectar, and dung liquid, these pests not only induce significant irritation but also serve as vectors for afflictions like pinkeye and Thelazia eyeworms.
The male face fly, primarily concerned with reproduction, spends little time directly on the cattle, preferring instead to perch on foliage, fence posts, and other surfaces. Meanwhile, the female deposits her eggs in fresh cattle manure, where they undergo a transformation from maggot to adult over a span of 2 to 3 weeks, depending on ambient temperature.
Maggot in a Dung Pat on Pasture
Combatting face flies requires a multifaceted approach:
- Environmental Modifications: Face flies shy away from enclosed spaces, making the provision of sheds or barns a strategic move to offer relief during peak fly seasons.
- Pasture Management: Regularly dragging or harrowing paddocks can disrupt the flies’ preferred breeding grounds, reducing their habitat and impeding their life cycle.
- Organic Solutions: For organic producers, approved forms of pyrethrum and other natural repellents offer some relief, though their efficacy may be limited to short durations.
- Insecticidal Measures: When faced with significant infestations, judicious use of insecticides becomes necessary. However, it’s crucial to apply them only when populations exceed the action threshold. Various methods, including sprays, back rubbers, face rubbers, and dust bags, can effectively target the areas where face flies congregate. Ear tag have shown some control as well.
- Researching Solutions: VetPestX, a valuable resource for selecting suitable insecticides tailored to specific pasture conditions, can aid producers in making informed choices. https://www.veterinaryentomology.org/vetpestx
By employing a combination of these strategies, producers can mitigate the nuisance and potential health hazards posed by face flies, ensuring the well-being of their cattle and the productivity of their operations. In future issues of the blog, I will discuss biological control.
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