Scheduled sanitation to reduce stable fly (Diptera: Muscidae) populations in beef cattle feedlots

Stable fly outbreaks in Brazil: a 50-year (1971-2020) retrospective

Over the last decades, stable fly (Stomoxys calcitrans) outbreaks associated with agricultural and/or livestock production systems have become a serious problem in some Brazilian locations. This article presents a survey on the history, evolution and mapping of such outbreaks in Brazil over five decades (1971-2020). Outbreaks (n= 579) were recorded in 285 municipalities from 14 states, mainly associated with by-products from the ethanol industry (82.7%), in natura organic fertilizers (12.6%) and integrated crop-livestock systems (3.1%). Few cases were reported until the mid-2000s, progressively increasing since then. Outbreaks associated with ethanol mills occurred in 224 municipalities, mainly in Southeast and Midwest states, while those associated with organic fertilizers (mainly poultry litter and coffee mulch) affected 39 municipalities, mostly in the Northeast and Southeast states. More recently, outbreaks in integrated crop-livestock systems during the rainy season have occurred in Midwest states. This survey highlights the magnitude of the problem of stable fly outbreaks in Brazil and its relationship with environmental public policies, agricultural production chains and regional trends. Specific public actions and policies are urgently needed to prevent their occurrence and impact in the affected regions.

Stable fly activity is associated with dairy management practices and seasonal weather conditions

Stable flies (Stomoxys calcitrans) are blood-sucking insects commonly associated with cattle production systems worldwide and are known to cause severe irritation to cattle due to painful bites. Cattle react to biting stable flies with an aggregating behavior known as bunching. Bunching behavior reduces grazing or feed consumption and thus reduces cattle productivity and welfare. Cattle’s fly-repelling behaviors include foot stomping, head tossing, tail switching and skin twitching. A longitudinal study was conducted in 2017 on 20 California dairies (average lactating herd size = 2,466 (SE±28.392)) during the stable fly season from April to July. The study objectives were to estimate the association between environmental factors and dairy characteristics including facility design, feed and manure management, total mixed ration (TMR) components fed to cattle, and operational pest management procedures and the outcome stable fly activity on California dairies. Stable fly activity was measured by counting stable flies on cow forelimbs (leg count) and on Alsynite traps (trap count) over the 13-week study period. Weekly leg counts were performed for cattle in lactating cow pens (31 pens from 10 study dairies) with counts made during the morning (AM) and again during the afternoon (PM). Trap counts were performed on all 20 study dairies. Data were analyzed using linear mixed models which revealed temporal variation in the average leg and trap counts with stable fly activity increasing from May to June and then decreasing to the lowest activity in July. Leg counts were higher during the afternoon compared to morning. Ambient temperatures ≤30⁰C and relative humidity (RH) measurements <50% were associated with higher leg and trap counts. Traps located at the periphery of study dairies had higher stable fly counts compared to traps located in the interior of the dairy. Cow pens with trees on the periphery had higher leg counts in comparison to pens away from trees. Specific TMR components were associated with both leg and trap counts. Dairies feeding by-products including almond hulls, wet distillers’ grain, fruits, and vegetables had higher trap counts compared to dairies that did not feed these ingredients. At the pen level, pens with rations that contained straw had lower average leg counts compared to pens fed with rations that did not contain straw. A similar association was observed for pens with rations that contained wheat silage when ambient temperatures were ≤30⁰C. In contrast, pens with water added to the TMR while the RH was ≥50% had higher average leg counts compared to pens without water added to the TMR. Dairies that applied insecticides for fly control to their entire facility had lower trap counts compared to dairies that did not apply insecticides. Stable fly activity measured on California dairies using leg and trap counts varied according to the month, environmental factors, pen surroundings, trap location, TMR components, and insecticide use.

Establishing a Method to Evaluate the Efficacy of Compounds Aimed at Repelling Horn Fly (Diptera: Muscidae) Infestations on Cattle in a Laboratory Setting

Use of nonpesticidal chemicals to minimize or eliminate horn fly (Haematobia irritans) populations on cattle could be helpful in combating insecticide resistance. One recent approach is the use of natural products with repellent properties against the target pest. A rapid on-animal evaluation system that accounts for both host and pest interactions and bypasses the need for costly multiyear field assessments is needed. The objective of this study was to develop a system to quantify product repellency of horn flies on cattle in a laboratory setting. Animal pair treatment groups were utilized to assess product efficacy and carrier effects across three experimental trials. A treatment solution consisting of 3% geraniol in mineral oil was the natural product repellent. Horn fly populations on animal pairs receiving the geraniol treatment were significantly reduced when compared with untreated animal pairs. However, animal pairs receiving a mineral oil-only treatment showed reduced horn fly populations similar to animals treated with mineral oil plus geraniol. Thus, there was a strong carrier effect that could be difficult to distinguish in the field but was easily observed using laboratory methods.

A Historical Review of Management Options Used against the Stable Fly (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), remains a significant economic pest globally in situations where intensive animal production or horticultural production provide a suitable developmental medium. Stable flies have been recorded as pests of livestock and humans since the late 1800s to early 1900s. Over 100 years of research has seen numerous methodologies used to control this fly, in particular to protect cattle from flies to minimise production losses. Reduced milk production in dairy cows and decreased weight gain in beef cattle account for losses in the US alone of > $2000 million annually. Rural lifestyles and recreation are also seriously affected. Progress has been made on many control strategies against stable fly over a range of chemical, biological, physical and cultural options. This paper reviews management options from both a historical and a technical perspective for controlling this pest. These include the use of different classes of insecticides applied to affected animals as toxicants or repellents (livestock and humans), as well as to substrates where stable fly larvae develop. Arthropod predators of stable flies are listed, from which potential biological control agents (e.g., wasps, mites, and beetles) are identified. Biopesticides (e.g., fungi, bacteria and plant-derived products) are also discussed along with Integrated Pest Management (IPM) against stable flies for several animal industries. A review of cultural and physical management options including trapping, trap types and methodologies, farm hygiene, scheduled sanitation, physical barriers to fly emergence, livestock protection and amendments added to animal manures and bedding are covered. This paper presents a comprehensive review of all management options used against stable flies from both a historical and a technical perspective for use by any entomologist, livestock producer or horticulturalist with an interest in reducing the negative impact of this pest fly.

Spatial repellency, antifeedant activity and toxicity of three medium chain fatty acids and their methyl esters of coconut fatty acid against stable flies

BACKGROUND

Stable flies are one of the most detrimental arthropod pests to livestock. With changing climates and agronomic practices, they expand their roles as pests and disease vectors as well. Their painful bites reduce livestock productivity, annoy companion animals, and interfere with human recreational activities. Current management technologies are unable to effectively control stable flies. The present study reports new results concerning the contact, spatial repellency, and toxicity of a bio-based product, coconut fatty acid and their methyl ester derivatives of free fatty acids of C_8:0 , C_10:0 and C_12:0 to stable flies.

RESULTS

Three medium chain fatty acid methyl esters (C_8:0 , C_10:0 and C_12:0 ) showed strong antifeedant activity against stable flies and their strengths were dose-dependent. Only the C_8:0 acid, C_8:0 - and C_10:0 methyl esters elicited significant antennal responses. Laboratory single cage olfactometer bioassays revealed that coconut fatty acid and C_8:0 methyl ester displayed active spatial repellency. All three methyl esters showed strong toxicity against stable flies.

CONCLUSION

Antifeedant activity is the main method through which coconut fatty acid deters stable fly blood-feeding. The C_8:0 , C_10:0 and C_12:0 methyl esters act not only as strong antifeedants, but also possess strong toxicity against stable fly adults. Limited spatial repellency was observed from coconut fatty acid and C_8:0 methyl ester. © 2019 Society of Chemical Industry.

Environmental Parameters Associated With Stable Fly (Diptera: Muscidae) Development at Hay Feeding Sites

Substrates composed of hay residues, dung, and urine accumulate around winter hay feeding sites in cattle pastures, providing developmental habitats for stable flies. The objective of this study was to relate physiochemical and microbial properties of these substrates to the presence or absence of stable fly larvae. Properties included pH, temperature, moisture, ammonium concentration, electrical conductivity, and numbers of coliform, fecal coliform, Escherichia coli, and Enterococcus bacteria. Each physiochemical sample was classified as a function of belonging to one of the three 2-m concentric zones radiating from the feeder as well as presence or absence of larvae. In total, 538 samples were collected from 13 sites during 2005-2011. Stable fly larvae were most likely to be found in moist, slightly alkaline substrates with high levels of ammonium and low temperature. The probability of larvae being present in a sample was the highest when the moisture content was 347% relative to dry weight and the average pH was 8.4. Larvae were recovered within all zones, with a nonsignificant, but slightly higher, percentage of samples containing larvae taken 2-4 m from the center. All methods used to enumerate bacteria, except total coliform, indicated decreasing concentrations in hay bale residue throughout the summer. In addition to the environmental parameters, cumulative degree day 10°C had a significant effect on the probability of observing stable fly larvae in a sample, indicating that unidentified seasonal effects also influenced immature stable fly populations.

Temporal changes in the bacterial community of animal feces and their correlation with stable fly oviposition, larval development, and adult fitness

Stable flies are blood-feeding insects with a great negative impact on animals world wide. Larvae develop primarily in animal manure and bacteria are essential for larval development; however, the principle of this dependence is not understood. We hypothesized that as the microbial community of animal manure changes over time, it plays an important role in stable fly fitness. Two-choice bioassays were conducted using 2 week old horse manure (control) and aging horse manure (fresh to 5 week old) to evaluate the effect of manure age on stable fly oviposition. Our data showed that fresh feces did not stimulate oviposition and that the attractiveness increased as manure aged but started to decline after 3 weeks. Bioassays assessing the effect of manure age at the time of oviposition on larval development demonstrated that 1–3 week old manure supported larval development significantly better than fresh, 4, and 5 week old manure. In addition, adult fitness (body size) was significantly higher in flies from 1 and 2 week old manure comparing to that of all other treatments. Analysis of the bacterial community of aging horse manure by 454-pyrosequencing of 16S rDNA revealed a great reduction in bacterial diversity and richness from fresh to 1–5 week old manure and a major shift from strict anaerobes in fresh manure to facultative anaerobes and strict aerobes in aged manure. Overall, the microbial community of 2 and 3 week old horse manure with its dominant bacterial taxa Rhizobium, Devosia, and Brevundimonas stimulated stable fly oviposition the most and provided a suitable habitat for larval development. These bacteria represent the candidates for studies focused on better understanding of stable fly – microbial interactions.

Nuisance flies on Australian cattle feedlots: immature populations

Species composition, seasonality and distribution of immature fly populations on a southern Queensland feedlot during 2001-2003 were determined. Similar data were collected on feedlots in central New South Wales and central Queensland. The fly species recovered in the highest numbers were Musca domestica L. (Diptera: Muscidae), Stomoxys calcitrans L. (Diptera: Muscidae) and Physiphora clausa Macquart (Diptera: Ulidiidae). Houseflies were the dominant species at all feedlots. Houseflies preferred the warmer months from October to June, but stable flies preferred the cooler months and peaked in spring (September-November) and autumn (March-May). Larval abundance ratings recorded in the feedlot and numbers of larvae extracted in the laboratory from corresponding samples followed similar trends. Larvae of M. domestica were most abundant in the hospital and induction area and least abundant in horse stables and yards. Pupae of M. domestica were abundant in the hospital and induction area and drains, but least abundant in horse stables and yards. Larvae of S. calcitrans were most abundant in drains and least abundant in horse stables and yards. Pupae of S. calcitrans were most numerous in drains and least numerous in old cattle pens. Feedlot design and management had little effect on fly reduction.

Economic impact of stable flies (Diptera: Muscidae) on dairy and beef cattle production

Stable flies, Stomoxys calcitrans (L.), are among the most damaging arthropod pests of cattle worldwide. The last estimate of their economic impact on United States cattle production was published 20 yr ago and placed losses at $608 million. Subsequently, several studies of effects of stable flies on beef cattle weight gain and feed efficiency have been published, and stable flies have become increasingly recognized as pests of cattle on pasture and range. We analyzed published studies and developed yield-loss functions to relate stable fly infestation levels to cattle productivity, and then estimated the economic impact of stable flies on cattle production in the United States. Four industry sectors were considered: dairy, cow-calf, pastured stockers, and feeder cattle. In studies reporting stable fly infestation levels of individual herds, median annual per animal production losses were estimated to be 139 kg of milk for dairy cows, and 6, 26, and 9 kg body weight for preweanling calves, pastured stockers, and feeder cattle, respectively. The 200,000 stable flies emerging from an average sized winter hay feeding site reduce annual milk production of 50 dairy cows by an estimated 890 kg and weight gain of 50 preweanling calves, stockers, or feeder cattle by 58, 680, or 84 kg. In 2009 dollars, the value of these losses would be $254, $132, $1,279, or $154, respectively. Using cattle inventories and average prices for 2005-2009, and median monthly infestation levels, national losses are estimated to be $360 million for dairy cattle, $358 million for cow-calf herds, $1,268 million for pastured cattle, and $226 million for cattle on feed, for a total impact to U.S. cattle industries of $2,211 million per year. Excluded from these estimates are effects of stable flies on feed conversion efficiency, animal breeding success, and effects of infested cattle on pasture and water quality. Additional research on the effects of stable flies on high-production dairy cows and nursing beef calves is needed to increase the reliability of the estimates.

Potential impacts of climate change on stable flies, investigated along an altitudinal gradient

Adult populations of stable flies were sampled along an altitudinal transect in Reunion Island to determine whether higher temperatures were associated with: (a) higher numbers of flies; (b) a longer season of infestation, and/or (c) different responses to warming in the cosmopolitan Stomoxys calcitrans (L) and the tropical Stomoxys niger niger Macquart (Diptera: Muscidae). Flies of both species were trapped at seven farms situated at four altitudes (100-1600 m a.s.l.) over a 90-week period. For both species, there were no relationships between the maximum or mean fly abundance and altitude. Only minimum abundance in winter was significantly higher at lower altitudes. Maximum and mean abundances differed significantly between nearby farms under similar climatic conditions. Seasonal fluctuations in fly abundance changed along the gradient. At lower altitudes, population growth started earlier after the winter but abundance declined earlier in summer, which resulted in a shift of the season of infestation. Seasonal fluctuations of both species were strongly related to climate variables at high altitude, mainly temperature. However, climate variables explained a decreasing proportion of the variations in abundance at lower altitudes. Stomoxys calcitrans was the most abundant species overall, but the proportion of S. n. niger increased significantly at lower altitudes and this species became predominant at 100 m a.s.l. It is concluded that stable fly infestations are unlikely to worsen in response to global warming. Maximum abundance is limited by local factors, possibly larval resources, which suggests that adequate husbandry practices could override the impact of climate change. Because S. n. niger tends to be the predominant pest at elevated temperatures, it is recommended that this species should not be introduced in areas where climate is changing.

Relationships between chemical properties of larval media and development of two Stomoxys species (Diptera: Muscidae) from Reunion Island

The development of two cattle pests, Stomoxys calcitrans L. and Stomoxys niger niger Macquart (Diptera: Muscidae), was studied in the laboratory using seven potential larval media from a dairy farm on Reunion Island. The media were six types of cattle feed and an old manure medium. Egg-to-adult survival, duration of development, and adult live weight at emergence were determined for both fly species on each medium. The media were analyzed for pH, nitrogen, organic matter, and structural compounds (cellulose, hemicellulose, lignin). For S. calcitrans, immature survival was significantly higher on sugarcane leaves, Rhodes grass, and elephant grass; for S. niger, survival was significantly higher on the same substrates plus sugarcane tops. These substrates were characterized by slightly acid pH values (range, 5.4-6.0). In both species, there were significant bell-shape relationships between immature survival and substrate pH. The developmental time of both fly species was significantly shorter on Rhodes grass, Rhodes grass hay, and elephant grass. These substrates were characterized by high cellulose contents and low soluble organic fractions. In both species, there were significant linear relationships between developmental time and cellulose content of substrates. Similarly, there were significant linear relationships between adult live weight and cellulose content of substrates. The C:N ratio of the most favorable substrates was highly variable. Although the relationships revealed in this study do not establish causation, it is suggested that pH and cellulose content may have direct and indirect effects on Stomoxys development.

Relationships between stable fly infestation with some physical facility characteristics and sanitation practices in several dairy farms in the State of Aguascalientes, Mexico

The possible relationships between stable fly infestation with dairy farm facilities and sanitation practices were studied using path analysis. Twelve dairies located in four counties of Aguascalientes dairy region were selected. The dairies were monitored from May to November 2003. In each occasion, fly infestation, individual physical facility characteristics, and sanitation practices were recorded. In all, 11 independent variables were involved in the study and related variables were grouped together and analyzed in two blocks by path analysis for each one of five population events (begin of fly season, first peak, fluctuation, second peak and decrease). There were significant regression coefficients only in the second peak for two variables, the distance to the silos and the distance to the dung heap (r(2)=0.96 for the full model). Among the 11 variables examined in the study, none had a statistical significant indirect contribution to fly infestation; direct contribution was observed for distance to the silos and for distance to the dung heap variables. However, only the distance to the silos variable was significantly related to stable fly Infestation.

Large sticky traps for capturing house flies and stable flies in dairy calf greenhouse facilities

Large sticky traps were evaluated for stable fly, Stomoxys calcitrans (L.), and house fly, Musca domestica L., (Diptera: Muscidae) capture under field conditions in 5 dairy calf greenhouse facilities in New York. The farm with the highest stable fly capture had the highest house fly capture, and the farm with the lowest stable fly capture had the lowest house fly capture, suggesting that fly management practices greatly influenced trap captures. In general, stable fly populations, as reflected by increased trap capture, generally rose during the summer. Numbers of flies counted on calves did not increase, however, suggesting that the traps greatly reduced the potential stable fly pressure on the calves as the fly population increased. Estimated number of stable flies and house flies captured during this 10-wk study exceeded 142,000 and 900,000, respectively. Producers were generally pleased with the trap performance and most felt that these traps reduced flies in their calf greenhouses to acceptable levels.

Abundance of stable flies on heifers treated for control of horn flies with organophosphate impregnated ear tags

Ear tags containing 40% organophosphate insecticides (diazinon or diazinon plus chlorpyrifos-ethyl) were applied to control Haematobia irritans (L.) (Diptera: Muscidae) in treated (TG01 and TG02) and untreated (UG01 and UG02) groups of Holstein heifers born in 2001 and 2002, respectively. Control and treated groups were assessed for the abundance of Stomoxys calcitrans (L.) (Diptera: Muscidae) from August 2001 to April 2002 and again from August 2002 to April 2003. The treatment had a high efficacy for control of horn flies (maximum median number per heifer of TG01 and TG02 = 5) but a low effect on the abundance of stable flies. The total numbers of S. calcitrans were 1251 (42.9% of the total) and 1668 (57.1%) for TG01 and UG01, and 1423 (48.8%) and 1494 (51.2%) in TG02 and UG02, respectively. No significant difference in stable fly burden was found in 55 of the 76 weeks evaluated. A unimodal peak of abundance in the spring was found during the first fly season, and a bimodal abundance, with peaks in the spring and autumn, during the second season. No strong associations between horn fly and stable fly burdens was found in individuals of the CG01 (correlation coefficient = 0.13, P > 0.05) or CG02 (correlation coefficient = 0.538, P < 0.05, determination coefficient = 0.289).