Integratedpest management

of �ies in Texas dairies

12-97

Contents

3 Fly management problems

Insecticide resistance, environmental regulations and public opinion are increasing the need for

an integrated approach to fly management.

4 Major pest flies

Knowing the biology of the major pest flies — houseflies, stable flies, horn flies, garbage flies

and blow flies — can help producers manage them successfully.

6 Integrated pest management

Integrated pest management (IPM) links many control methods into one system that reduces

dependence on chemicals.

7 Sanitation

To implement a successful IPM program, begin with sanitation and manure management.

8 Biological control

Fly populations can be suppressed by using beneficial insects and arthropods, predators and

parasites.

10 Chemical control

Chemicals used for fly control must be applied to specific areas. For adult flies, chemicals are

used in sprays, mists, self-application devices, baits and traps. Larvae are suppressed with sprays

and feed-through or oral larvicides.

14 Scouting

Scouting is essential to find breeding sites and to decide where to release parasites and to apply

larvicides and additional sanitation.

16 Principles of fly control

Nine principles govern fly control in dairies and provide excellent guidelines in your pest-

management program.

FLIES IN DAIRIES are managed bestwhen producers coordinate severalmethods that together offer good con-

trol at low cost. Called integrated pest man-agement (IPM), this approach reduces depen-dence on chemicals, instead combining sani-tation practices, biological control and chemi-cal agents to reduce fly populations.

The integrated approach to fly control isneeded because:

• Fewer effective fly-control insecticidesare available.

• Flies are becoming more resistant to in-secticides.

• New regulations require reductions ofinsecticide residues in food.

• People need to reduce their exposure toinsecticides.

• Dairy systems are expanding, producingmore intense fly breeding.

• Concern is growing over the cost/benefitsof fly control in dairies.

• Flies harm animals and lower milk pro-duction.

• The public is more aware of the healthand annoyance problems flies cause.

Dairy producers need to understand the fac-tors producing fly populations, including cli-mate, regional terrain, management practicesand production facility design. To keep flypopulations the lowest at the least cost, pro-ducers should take action at decisive times inthe pests’ life cycle. Knowing the biology ofthe major fly pests — houseflies, stable flies,horn flies, garbage flies and blow flies — canhelp producers implement a successful dairyIPM program.

Integrated pest managementof flies in Texas dairies

Douglass E. Stevenson and Jesse Cocke*

* Extension associate; Extension entomologist; The Texas A&MUniversity System

Dairies that control flies can increase production and reduceannoyance and disease spread.

Housefly Musca domestica L.

The most common, most prolific and mostcostly fly pest in dairies is the housefly (Fig-ure 1). Besides annoying animals and people,houseflies spread diseases from animal to ani-mal and to humans.

Life cycleThe housefly passes through four life

stages: egg, larva (maggot), pupa and wingedadult. Under ideal conditions, the life cyclemay be as short as six days. In Texas, twoto three generations may develop per monthduring warm months. Adult female flies havebeen known to lay more than 2,000 eggs, butnormally produce about 500 to 600 eggs dur-ing their lifetime. Eggs are laid in clusters of75 to 150 every three to four days during a31-day period.

Flies usually deposit eggs in wet, decayingorganic matter such as manure and spilled feed.After hatching, the cream-colored fly larva, ormaggot (Figure 2), feeds from four to six days.The fly grows during the larval stage, the sizeof the adult being dependent on how big thelarva grows during feeding.

After feeding, the maggots crawl away frommoist feeding areas to a dry habitat to pupate.They may spend three to four days in thisprepupal or migratory stage before pupatingin dry feed or manure. Once at rest, the larvatransforms into a brown, nonfeeding seed-likepupa. The pupa remains stationary until itemerges from the old larval and pupal skins asan adult fly.

Under ideal conditions, houseflies multiplyquickly. Just one pound of wet manure canyield more than 1,500 maggots. It is possiblefor 1,000 pounds of wet manure to harbor 1.5million larvae. This means that even smallbreeding areas can produce many flies.

Economic importanceHouseflies can spread diseases and para-

sites from one animal to another and to hu-mans. Their feeding method and ability tocarry diseases make them a constant threat tomilk production and animal and human health(Table 1).

The housefly can consume food only in liq-uid form. When feeding, it frequently regurgi-

tates droplets of food and saliva from its spong-ing mouthparts (Figure 3). Regurgitation helpsthe f ly l iquefy solid food. Then it canreconsume the mixture as it feeds on variousfood sources.

Male and female adult flies eat feed, excre-ment and other decaying organic matter. Theyusually pick up pathogens and parasites bywalking over materials containing them, con-taminating their wings and feet. When feed-ing, the flies’ intestinal contents also becomeloaded with disease agents. The flies redepositthe disease agents each time they defecate, feedor vomit.

In a dairy, heavy housefly populations cancause serious economic problems (Table 2). Vi-rus diseases carried by flies include bovinevirus diarrhea (BVD), the bovine herpesvirus(BHV-1) causing infectious bovine rhinitis(IBR), and parainfluenza 3 (PI3). Fly-bornebacterial diseases include pink eye, mastitis,bacterial scours, typhoid, anthrax, vibriosisand several clostridial diseases.

Houseflies have harbored more than 100different species of pathogenic organisms.Studies have incriminated them in more than65 human and animal diseases. They also cantransport eggs and infectious larvae of severalimportant parasitic worms.

Economic thresholds have not been estab-lished for housefly populations in dairies.However, nuisance levels (Table 3) that annoyanimals correlate closely with the incidenceof such diseases as pink eye and mastitis. Tol-

HOUSEFLY PROBLEMS

Table 1. Economic problems fromhigh housefly populations in dairyoperations.

• Reduce milk production through annoyance

• Annoy humans and interfere with work suchas milking and feeding

• Increase frequency of animal disease

• Raise disease medication costs

• Increase veterinary service costs

• Prompt complaints and legal action from thepublic

• Increase the potential for spread of conta-gious human diseases

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Fig. 1. Housefly adult

Fig. 2. Housefly maggot

Fig. 3. Housefly regurgi-tating while feeding

erance levels often depend on the size of thearea infested with flies.

Left unmanaged, houseflies can irritatecows, lowering feed conversion and milk pro-duction. Similarly pink eye, mastitis and otherinfectious diseases may spread more rapidlythrough the herd. Cow irritability and diseaseraise labor, medication and veterinary costs.Income also drops with production losses.

Stable fly Stomoxys calcitrans (L.)

The stable fly (Figures 4 and 5) feeds onblood. Although it is in the same family as thehousefly and resembles it slightly, the stablefly bites aggressively. It is easily distinguishedfrom the housefly by its piercing-suckingmouthparts, which it carries in a sheath pro-jecting forward from under the head. Whenfeeding, the stable fly inserts its mouthpartsinto the host to withdraw blood. Both malesand females feed on blood, frequently chang-ing position on the animal or moving to otherhosts until they have engorged themselves withblood.

Stable flies also differ from houseflies inthat they require a looser, drier environmentand a superior diet. Stable flies prefer an un-digested food supply higher in protein. Theybreed in decaying hay, straw, grain and mix-tures of grain, manure and hay residue. Idealbreeding sites are manure piles containingmixtures of manure, urine-soaked bedding,straw and undigested feed. Stable flies developless well in manure than in manure mixed withundigested food.

Life cycleThe female stable fly crawls into loose

breeding material and deposits from 25 to 50eggs at each egg-laying site. It may lay as manyas 600 eggs during its lifetime. In about threedays, the eggs hatch into larvae, which feedfor about two weeks before transforming intothe nonfeeding pupal stage. In about 10 days,the adult stable fly emerges. On average, thelife cycle from egg to adult requires about 28days.

After mating, female adults return to theirbreeding sites to lay eggs. Soggy, fermentinghay and manure residue left in piles or underfeed bunks is an ideal habitat for larval devel-opment. Old straw piles that remain moist dur-ing spring, summer and fall can harbor largefly populations.

Economic importanceStable flies irritate cattle during resting,

feeding and milking. Research shows that highpopulations of stable flies can lower milk pro-duction by 15 to 30 percent.

Stable flies usually bite during daylighthours. They can irritate cows so severely dur-ing milking that some cows kick off their milk-ers. They also bite humans and can tormentworkers during milking and feeding. Stableflies may travel several miles to find bloodmeals and suitable breeding sites.

The stable fly also can carry several ani-mal diseases, including anthrax and trypa-nosomiasis.

Fig. 4. Stable fly adult

Fig. 5. Stable fly adult,side view

MILK PRODUCTION LOSS

Table 2. Milk production loss relatedto stable flies.

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NUISANCE LEVELS

Table 3. Nuisance or tolerance levelsfor houseflies

Dairy location Mean no. flies

Milk holding room 50 total

Milking parlor (closed) 200 total

Milking parlor (open) 400 total

Building walls 100/100 sq. ft.

Feeding lanes (per side) 100/10 linear ft.

Commodity surfaces 200/100 sq. ft.

Commodity barn walls 100/100 sq. ft.

Open lot holding areas 200/100 sq. ft

Cows 20-40 per head

Calves 10-20 per calf

Horn fly Haematobia irritans (L.)

About half the size of the housefly or stablefly, the horn fly (Figure 6) is similar in colorto the stable fly and also feeds on blood. Hornflies remain on the cow all the times. Femalesleave the animal only to deposit eggs on freshmanure.

Life cycleA horn fly lays eggs in groups of three to

seven on the manure surface, rarely deposit-ing more than 20 eggs. Larvae hatch within 24hours. They develop rapidly, reaching com-plete growth in three to five days. Then theycrawl to drier parts of the manure to pupate,and remain in the pupal stage six to eight daysbefore emerging as adults.

Under ideal conditions, the entire life cyclefrom egg to adult takes from 10 to 14 days.After emerging, adults fly to animals wherethey remain.

Economic importanceConstant feeding by heavy horn fly popu-

lations annoy, irritate and take blood fromcattle, causing them to lose weight and eatmuch more feed than necessary. Cows heavilyattacked by horn flies may lose half a poundof body weight per day. Milk production maydrop as much as 10 to 20 percent.

Garbage and blow fliesBlack garbage flies (Ophyra spp.)

Sometimes called “dump flies,” garbageflies (Figure 7) are shiny black and about two-thirds the size of houseflies, with a similar lifecycle. Garbage flies breed in the same habitatas houseflies and may become very abundant.Two species, Ophyra ignava (Harris) andOphyra aenescens (Wiedemann), inhabit con-fined animal facilities in the United States.

Garbage fly larvae feed on housefly larvaeand may reduce housefly numbers while in-creasing their own. They may become almostas annoying as houseflies when the two occurtogether.

Blow flies (Family Calliphoridae)

Several species of blow flies, including theblack blow fly (Figure 8), Phormia regina(Meigen), inhabit confined animal productionfacilities. They are robust flies with a metallicsheen to the body. Species vary in color, rang-ing from green and blue to bronze-black andthe color of a new penny. Ordinarily larger thanhouseflies, green blowflies and blue blowflieshave stout bristles but no stripes on the backor thorax (Figures 9 and 10).

The blow fly life cycle is similar to thehousefly’s. It passes from white eggs throughthree larval (maggot) stages (Figure 11), a pu-pal and an adult stage. To develop, however,blow flies require a wet medium and a diet richin animal protein. They prefer to breed in de-composing animal carcasses, afterbirth andareas contaminated with spilled milk. Thoughless well, they can develop in decaying ma-nure and spilled feed when other food sourcesare unavailable.

Good sanitation can prevent major problemswith garbage and blow flies.

Integrated pestmanagement - IPM

Dairy flies can be managed effectively andeconomically using integrated pest management.IPM is not a way to control pests, but a way ofthinking about pest control. It links many con-trol methods into one system, excluding any thatdisrupt or diminish the effectiveness of the oth-ers. In IPM, all control methods must supporteach other.

Figure 12 shows a decision-making flow chartthat includes four courses of action: chemical;larvacide-supplemented; IPM; and spray-as-needed, late-season suppression. All but the IPMprogram depend almost exclusively on chemicalcontrol methods. Larvicide-supplemented controlis simply a variation of chemical control.

The spray-as-needed plan to defer any actionuntil flies reach problem levels carries the high-est risk. Putting off a decision until later in theseason or adopting a “wait-and-see” attitude al-lows fly populations to explode. Sometime in midor late summer, fly populations will multiply outof control. No amount of late-season spraying

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Fig. 6. Horn fly

Fig. 7. Black garbage fly

Fig. 8. Black blow fly

INTEGRATED PEST MANAGEMENT - IPMFig. 12. Dairy fly pest management decision making flow chart for planning IPMactions for season-long fly control

will bring an exploding population under con-trol. The flies will have the day.

The IPM strategy uses as many nontoxic ornonlethal methods as possible to suppress flypopulation growth. It unites sanitation, biologi-cal control and chemical agents to manage flieseffectively and economically. Compared to otherapproaches, the IPM method usually presents thelowest expenses and risks.

Dairy fly IPM activities should begin in win-ter or spring before flies are active and continue

until fly activity shuts down at the end of theseason. A good fly-control plan includes sanita-tion, biological control and chemical agents.

SanitationTo implement a successful IPM program,

begin with sanitation and manure management.Spring is a good time to remove and spreadmanure and to suppress overwintering flies. Atlower temperatures, flies are frequently more

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Season-long Suppression

Chemical LarvacideSupplemented

I.P.M.

EarlySpring

SpringCleanup

LateSpring

EarlySummer

Manure removaland spreading

Applyresidual sprays

Manure removaland spreading

Start feedingoral larvacides

Residual sprays

Manure removaland spreading

Kill overwintering fliesw/pyrethrins or othernonpersistent agent

Start feedingfeedthrough IGRs

Begin parasitoidreleases

Residual spraysand fogs

MidSummer

Residual spraysas needed

Begin baiting

Bi-weekly releaseof parasitoids

Begin regularfogging

Tank mixadulticides withresidual sprays

Residual spraysas needed

Spray & fogas necessary

Continue sprayprogram

Continue baiting

Selected spraysif control beginsto break down

Continue sprays

Discontinue orallarvacides

Begin intensive(sometimes daily)fogging and sprayingand continue as needarises for the rest ofthe season

LateSummer

Fall

Cont. intensivespraying, manuremanagement

END PROGRAM END PROGRAM END PROGRAM END PROGRAM

Spray-as-neededLate-season Suppression

SpringCleanup

▼

SpringCleanup

▼▼▼

Fig. 11. Blow fly maggots(side view)

Fig. 9. Green blow flyadult (top view)

Fig. 10. Blue blow fly

active than their natural enemies. This offersan opportunity to use short-term, nonresidualpesticides to reduce fly numbers.

Adopt these sanitation practices in earlyspring to prevent heavy housefly and stable flypopulations from developing:

• Clean and move calf hutches regularly.Elevate one side of the hutch to allowair circulation or provide ventilation inconstruction. Clean calf holding pensweekly if possible. Calf manure attractsflies rapidly.

• At least weekly, clean open feeding lanesand concrete corners where the feedstall(s) curb meets the drive-throughfeeding lane slab.

• Completely clean entrance and exit lanes(alleyways) to and from the milking areadaily or after each milking.

• To prevent floating mats on the edges oflagoons where anaerobic respiration hasdeclined, collect debris from runoff col-lection channels, sediment basins andretention ponds regularly.

• Keep the outside corners next to exitwalkways from barns weed-free. Cleanthem at least weekly. In these areas, ma-nure may wash over the curb to the out-side of walkways.

• Remove and spread straw and manurepiles frequently to eliminate stable flybreeding sites. Immediately dispose ofdead calves, cows and afterbirth to pre-vent disease spread and blow-fly breed-ing.

• Never allow silage residue to accumu-late at openings to pits on bagged silage.

• Scrape pens at least weekly to clean outmanure. Remove manure piles withinfive days. Maintain at least a 3 to 4 per-cent pen slope; avoid creating potholesduring pen scraping. Maintain broad,shallow sediment basins to keep solidsuphill away from runoff holding ponds.Use a separate drainage system fromeach pen. Keep the drain system at a uni-form slope of 3 to 4 percent from feedbunks to the back of the pen. Maintainthis slope through alleyways into maindrainage channels.

• To move manure from pen to pen forcomplete manure collection and piling,clean under fence lines using a tractorfront-end mounted push bar or othermethods.

• Clean manure spreaders regularly toprevent fly breeding.

• Prevent moisture from accumulating atthe entrances of feed holding facilities(commodity barns) and feed mixing ar-eas.

• Use vertical-sided feed bunks and watertroughs. Prevent manure from buildingup in these areas for more than sevendays. Use overflow drains on watertroughs to prevent water from overflow-ing into pens and feeding areas; fix wa-ter leaks.

• Move round bale feeders regularly to pre-vent manure, urine and hay buildup thatcan breed stable flies. To prevent house-fly and stable fly breeding, scrape, pile,remove and spread manure-straw mix-tures and clean under elevated feed bunksin pens.

Biological controlIn IPM, lethal methods target the pests and

avoid injuring helpful insects. To suppress flypopulations, dairy producers can use suchnatural enemies as black soldier flies, rat-tailedmaggots, beetles, mites and wasps.

Beneficial insects and arthropods

Black soldier fly [Hermetia illucens (L.)]

The black soldier fly (Figure 13) is a large(2 cm long) blue-black fly with black legs,white-yellow tarsi (feet) and two clear or trans-lucent areas on the dorsal part of its abdomen.Females prefer to lay eggs in drier areas of ma-nure, where they produce about 900 eggs inseveral batches, which hatch in about fourdays. Larvae pass through five instars over twoor more weeks. During feeding, the large lar-vae (Figure 14) churn and liquefy the manure,making it less suitable for house fly develop-ment.

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Fig. 14. Black soldier flylarvae

Fig. 15. Rat-tailedmaggot (syrphid flylarvae)

Fig. 13. Black soldier fly

Large populations of soldier fly larvae notonly reduce housefly larvae, but also discour-age houseflies from laying eggs in the samehabitat, such as in areas along drainage canalsand around settling basins and lagoons.

Rat-tailed maggot [Eristalis tenax (L.)]

The rat-tailed maggot (Figure 15) is the lar-val stage of the syrphid fly (Figure 16). Largeand cylindrical, the larva has a long filament-like tail projecting from the posterior end ofthe body, as the name implies. The tail is actu-ally a breathing tube with two openings, or spi-racles, at its tip. Surrounding the breathing tubeare tiny hairs that allow the tip to take in air atthe water surface. Larvae develop throughthree stages, each having a caudal projectionor tail. When fully mature, the third stage isabout 1 inch long.

Rat-tailed maggots gather in polluted liq-uid habitats such as run-off ditches, pools, set-tling basins and waste lagoons. They are im-portant because they aid in decomposition andreduce other fly breeding in these habitats.

Excessive pesticide run-off may kill rat-tailed maggots. Feed-through larvicides alsomay destroy these good fly larvae or impairtheir development. Premise sprays may killadults.

Predators (Beetles and mites)

Predatory beetles in the families Staphy-linidae and Histeridae feed on fly eggs andlarvae. Both larval and adult stages of thesebeetles are efficient fly predators. A smallblack beetle, the histerid, arcinops pumilo(Erichson), may consume 13 to 24 house flyeggs per day. Its larva eats two to three eggsper day. Dung beetles bury manure, aid in itsdecomposition and make it unsuitable for flylarval development (Figure 17).

Mite predators belonging to the familiesParasitidae, Macrochelidae and Uropodidaefeed on housefly eggs and first instar larvae.

Parasites (Wasps)

The fly parasites most commonly associatedwith dairy operations are small wasps (Figure18). Three genera in the wasp family Ptero-maldae are effective fly parasites: Muscidi-

furax, Spalangia and Pachycrepoideus. Themost common species in confined animal op-erations are Muscidifurax raptor Gerault andSanders; S. nigroaenea Walker, S. cameroniPerkins, S. nigroaenea Curtis; and Pachy-crepoideus vendemiae Rondani.

Female wasps of these species activelysearch for fly pupae. The female wasp piercesthe pupal skin and inserts a single egg into eachfly pupa. Once the egg hatches, the parasitedevelops through three larval instars whilefeeding on and killing the fly pupa. After feed-ing, the larva pupates inside fly pupal skin.Later, the mature wasp cuts a hole in the flypuparium and escapes as an adult parasite. Theparasitic wasp completes its entire life cyclein about three weeks.

Some adult parasites probe pupae and feedon the pupal exudate, killing the pupa withoutlaying eggs in it. As a result, many damagedfly pupae fail to develop into adult flies. Para-sitism of fly pupae on some dairies can reach4 percent, but 5 to 15 percent is much morecommon.

Another parasite species, Nasonia vitri-pennis Walker, lays many eggs per fly pupa,producing as many as seven to 10 adult para-sites from a single fly pupa. However, it isscarce, both naturally and where augmentivereleases have occurred.

Under certain conditions, augmentive re-leases of fly parasites may increase parasitismrates and reduce fly populations. However,little is known about augmentive parasite re-leases, including guidelines on the species,numbers, times and conditions of parasite re-leases. When considering parasite augmenta-tion, first use cultural and management tech-niques to increase the parasite populationsoccurring naturally.

Parasite species differ in their response toclimate, weather and micro-habitat. The sub-strate and its condition also affect certain para-site species’ ability to establish themselves.

Spalangia usually parasitize fly pupae bur-ied 3/8 inch or less deep in manure or substrate.Researchers found that Spalangia cameroniPerkins occurs more often in loose substratesregardless of moisture. However, studies showthat Spalangia nigroaenea Curtis prefers pu-pae in sheltered moist feed and wet straw.

Fig. 16. Syrphid fly

Fig. 17. Dung beetles

Fig. 18. Parasitic waspon fly pupa

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A drought-resistant strain of Spalangiaendius is active at lower temperatures and hy-bridizes with other strains of S. endius. Theoffspring of these crosses are stronger and livelonger.

Muscidifurax attack fly pupae 3/16 inchdeep or less in dry or moist manure under feedbunks, fence lines and manure piles. These spe-cies occupy the broadest niches on the dairy,reproducing in older pupae and in those para-sitized earlier by other parasites. They alsosurvive longer when hosts are not immediatelypresent.

Muscidifurax raptor and M. zaraptor are ap-parently less effective in hot, dry climates.However, a strain of M. zaraptor occurring inColorado and New Mexico can better resistclimate extremes and can forage better thanthose in California and the Midwest.

Dairies should release only those parasitesthat can effectively establish themselves. Toestablish itself, a parasite must find a suitablehost and reproduce on the host in sufficientnumbers to sustain population growth. A re-cent study of parasites released in Texas dair-ies showed that less than 15 percent of fly pu-pae contained parasites. Most of the parasiteswere species of Spalangia and Muscidifurax.The most efficient parasite was Spalangiacameroni, which accounted for about 41 per-cent of the parasites recovered. S. nigroaenaaccounted for another 17 percent; S. endius,14 percent; and Muscidifurax raptor and M.zaraptor, only about 5 percent. Various otherparasites accounted for the rest of the speciesrecovered from parasitized pupae.

Another two-year study rated commercialparasite release material from two companies.This study showed that the commercial mate-rial contained mainly M. zaraptor, M. raptorand S. endius in various frequencies during thespring and summer. No shipments containedS. cameroni nor S. nigroaenea, even thoughthese parasites establish most frequently onTexas dairies and feedlots.

The level of fly control to expect from adultparasites feeding or foraging on fly pupae isstill unknown.

Suggestions for using parasites

• Release only species that have shownability to establish themselves (Table 4).Ask dealers the composition of their re-lease material.

• To promote establishment, release para-sites in early spring.

• Practice maximum sanitation in earlyspring to reduce breeding sites and adultpopulations.

• Place parasites directly on specific remain-ing fly breeding sites in early morning orlate afternoon.

• Use at least 100 to 200 parasitized pupaeper square foot of breeding media saturatedwith maggots and pupae.

Chemical controlChemicals used for fly control must be ap-

plied to specific areas. Where proper sanitationoccurs, it is seldom justifiable to use premisesprays or pesticide applications to entire dairies.Most insecticides are broad-spectrum, killingpests as well as fly predators and parasites. Topreserve such natural enemies as mites, beetlesand wasp parasites, spray insecticides only whereflies and larvae are abundant. Such spot larvi-

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PARASITES

Table 4. Pteromalid parasitoids thathave established more and lessfrequently in Texas dairies andfeedlots.

Established most frequently

Muscidifurax zaraptor Kogan and Legner

Muscidifurax raptor Gerault and Legner

Spalangia nigroaenea curtis

Spalangia endius Walker

Spalangia cameroni Perkins

Established less frequently

Nasonia vitripennis

Urolepis rufipes (Ashmead)

Spalangia nigra Latrielle

Spalangia drosophililae (Ashmead)

Pachycrepoideus vindemiae (Rodani)

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cide applications reduce overall populations ofparasites and predators only slightly.

Reduce drift by applying surface sprays foradult flies as coarse droplets. Direct any re-sidual surface treatments to structures whereflies rest, such as upper partitions and the up-per parts of buildings that show fly spotting.

Houseflies develop resistance to insecticiderapidly. To avoid resistance, follow resistancemanagement practices strictly, alternating orrotating classes of insecticides. Do not usepyrethroids consecutively. Alternate them withorganophosphates or carbamates, but not withmethoxychlor or other DDT-related com-pounds, because both classes of insecticide af-fect the same target site. This means they bothproduce the same type of resistance. Pyre-throid-resistant flies also resist methoxychlor.

Also, DDT- and methoxychlor-resistantflies probably will resist pyrethroids. Whenusing pyrethroid surface sprays, use organo-phosphate dust bags or self-treatment devices.For organophosphate surface or premisesprays, use pyrethroid or methoxychlor dustbags or self-treatment devices.

For adult flies, chemicals are used in sprays,mists, self-application devices, baits and traps(Table 5). Surface applications of pesticidesare effective where adult flies gather or rest.Larvae are suppressed with sprays and feed-through or oral larvacides (Table 6). Larvicidalpesticide applications work where maggots areabundant and biological control has failed.

Adulticides

Sprays

Surface sprays are dilutions of pesticideformulations applied as coarse droplets. Ap-plied to walls, posts, ceilings and other struc-tures, formulations used as surface sprays in-clude wettable powders (WP) or emulsifiableconcentrates (EC). Surface sprays create along-lasting toxic surface to control flieswhere they rest. To wet surfaces completely,apply these sprays at pressures of about 40 psi,but not to the point of run-off. For small ar-eas, hand-pumped compressed air sprayersmay be the most economical.

Larger operations may require low-pressureroller or piston pumps driven by motors. Small

gasoline engines or power-takeoff equipmentserve this purpose well. Wettable powders orsoluble powders usually control flies longer.However, wettable powders require constantagitation to keep them from settling to the bot-tom of the tank. When applying wettable pow-ders as residual sprays for fly control, be surethe spray tank has bypass or mechanical mix-ing to keep chemicals suspended.

Mists

Mists are sprays with very small dropletsused exclusively to control adults. Mist drop-lets are so small that they float freely in the airand take a long time to settle, directly expos-ing adult flies to the insecticide as they flythrough the air. Insecticides used in mist spraysproduce quick knock-down and are useful asshort-term space sprays. Mists have little or nolong-term residual effect. They are most effec-tive when used to reduce quickly the numberof flies in and around facilities.

Tractor- and R.V.-mounted equipment isavailable for larger facilities. Small hand-car-ried or backpack equipment may be useful forlocalized applications. Hand-carried mist gen-erators are available in both gasoline- and elec-tric-powered versions. Misting equipmentbreaks insecticides into fine droplets either bymechanical means (rotating plates or vanes) orby shearing with high volume air or a combi-nation action.

Various concentrations of mists may be pro-duced by mixing active ingredients with eitherwater or oil solvents. Oil solvents include refinedkerosene, mineral oil or other organic solvents.Oil controls flies more rapidly. However, petro-leum products may irritate animals or present afire hazard. Ultra low volume (ULV) applicationequipment produces mists with undiluted highconcentration formulations, with particle sizesaround 15 to 30 microns in diameter.

Automatic misting systems installed with tim-ers are also available. They use “piped-in” insec-ticide mixes through nozzles at exit walkwaysand lanes. Connecting pressurized cylinders di-rectly to the system avoids the need for electricpower. Although convenient, automatic mistinghave several disadvantages: They are expensiveto install, maintain and operate; air currents maymove insecticide away from animals, wasting it;and drift may kill parasites far from the source.

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ADULTICIDES

Table 5. Adulticides for use on dairy flies.

Ectiban 5.7% E.C. - spray as per label

Insectiban 5.7% E.C. - spray as per label

Permectrin II 10% E.C. - spray as per label

LiquiDuster 1% - rope wick self treatment

Synergized DeLice 1% - 0.5 oz/100 lb or up to 5oz max

Permectrin 25% WP - 1 lb/50 gal water (wetanimals)

Permectrin 0.25% dust - 2 oz/animal or dust bag

Rabon 3% dust - 2 oz/animal or dust bag

Ear tags - provide only limited control of these flies

Premises:

Dairy barns

Dimethoate (cygon 23% E.C.) - 1 qt/6 gal water;use 1 gal mix/500 sq. ft.

Rabon 50 WP - 4 lbs/25 gal water; use 1 gal per500 sq. ft.

Permethrin - both WP ad EX formulations

Pyrethrins + Synergists - aerosol sprays

UV light + sticky board - change sticky boardsregularly

Other buildings

Diazinon 50 WP - restricted use (certified applica-tors only)

Naled (Dibrom 60% E.C.) - 3 pts/25 gal. water; use1 gal. spray/500 sq. ft.

Dimethoate (Cygon 23% E.C.) - 1 qt/6 gal water;use 1 gal spray/500 sq. ft.

Rabon 50% W.P. - 4 lbs/25 gal water; use1 gal/500 sq. ft.

Permethrin - WP and EC formulations as for adultfly applications (follow label)

Space sprays (blowers, foggers, mist systems)

Dibrom (36% E.C.) - 1 qt/40 gal water

Dibrom (1 % Ready-to-use) - 1 oz/3,000 cu. ft.

Ectiban 5.7% - mist undiluted 4 fl oz. per 1,000 sq.ft. surface

Insectiban 5.7% - 1 qt/12.5 gal diesel or mineral oil;use 4 fl. oz spray/1,000 sq. ft. in overhead system.

Atroban 11% E.C. - pt/10 gal diesel or mineral oil;use 4 fl. oz/1,000 cu. ft. in overhead system.

Permectrin II 10% E.C. - mist undiluted at 4 ozspray/1,000 sq. ft.

Pyrethrins + Synergist - follow label directions foreach product.

Horn flies: (on animal)

Pyrethrins + Synergist—use as needed(aerosol)

Permethrin:

Atroban 11% E.C.—use per label directions

Ectiban 5.7% E.C. - use per label directions

Insectiban 5.7% E.C. - use per label directions

Permectrin II 10% E.C. - use per labeldirections

LiquiDuster 1% - Rope wick in exit walkway self-treatment

Synergized DeLice 1% - 0.5 oz/100 lbs. up to5 oz/animal

Permectrin 25% WP - 1 lb/50 gal. water(wet animals)

Permectrin 0.25% dust - 2 oz/animal or dust bag

Rabon (tetrachlorvinphos) 3% dust - 2 oz/animalor Dust Bag

Marlate (methoxychlor) 50 WP - 1 Tablespoon/animal or Dust Bag

Ear tags (two/cow)

Ectrin (8.0% fenvalerate)

Atroban (10% permethrin)

Expar (10% permethrin)

Ear Force (10% permethrin

Gardstar Plus (10% permethrin)

Deckem (10% permethrin)

Perma-Tect (10% permethrin)

Perma-Tech II (10% permethrin + chlorpyrifos6.6%)

Ear Force Ranger (10% permethrin + 4.2% pbc)

MaxCon (7% cypermethrin + 5% chlorpyrifos 13%p.b.o.)

PYthon (10% zetamethrin + 10% p.b.o.)

Dusts

Co-Ral (coumaphos 1% dust) - follow labeldirections

Marlate (methoxychlor 50% WP) - follow labeldirections

Rabon (tetrachlorvinphos) - follow label directions

Houseflies and stable flies

Pyrethrins + Synergists - aerosol spray formulations

Permethrin (on animal)

Atroban 11% E.C. - spray as label

Use mists only when wet weather preventsproper sanitation, allowing adult fly popula-tions to become unacceptable.

Aerosol sprays under high pressure contain-ing natural pyrethrins, PBO, and syntheticpyrethroids are available for space sprays.Aerosol space sprays are most useful in milkholding rooms, milking parlors and otherbuilding spaces.

Self-application

A highly cost-effective way to control flieschemically is self-treatment. This method al-lows animals to treat themselves with insecti-cide using various devices that apply formula-tions directly to the animal. Self-applicationdevices include dusters, dust bags, liqui-dust-ers, and back rubbers and oilers. Various pes-ticides are labeled for use in self-applicationsystems, including synthetic pyrethroids, or-ganophosphates, and methoxychlor, a biode-gradable chlorinated hydrocarbon. When us-ing self-application systems, use caution andfollow label instructions.

Baits

Fly baits usually contain an insecticide suchas propoxur mixed with an attractive substancesuch as sugar or molasses. The most effectiveattractant is a pheromone such as z-9-tricosene.Other baits may contain the insecticide trichlo-rfon. Users also can prepare their own mix-tures, but results from homemade baits maybe somewhat erratic.

Traps

Traps are mechanical devices that captureand kill flies. Although properly belonging ina section outside chemical control, most trapsinvolve chemicals registered as pesticides ei-ther as attractants or killing agents. All trapsuse attractants to lure flies to destruction in acontainer, on a sticky surface or on an electricgrid. Some also contain an insecticide.

Traps come in many shapes, as simple aspaper with a sticky surface or as complex asan electronic fly “zapper.” Among the simplestand oldest traps are fly strips or fly paper,which have been used for more than a hun-dred years.

Container traps, variations of the old-fash-ioned bottle trap, are almost as old. They use

chemicals to lure flies into a container fromwhich they cannot escape and where they areheld until they die.

Some electronic traps use ultraviolet lightas an attractant. The light lures flies to acharged grid where a powerful current elec-trocutes them. Several electronic traps use bothlight and chemical attractants; they also mayuse a combination of electric grid and stickysurface to destroy flies. These are among themost complicated of all traps.

Many chemical attractants exist. The olderones are usually foul-smelling substances thatmimic the odor of fly food. Some newer at-tractants are odorless feeding or sex attracta-nts. The most powerful is z-9-tricosene, a sexand aggregation pheromone of the housefly.Used in most modern traps, z-9-tricosene hasthe common name Muscamone®.

Traps are useful where chemical use is dif-ficult or impossible, or where residual spraysor mists are ineffective or inconvenient. Theseareas include milk holding rooms, milkingparlors and feed holding and mixing areas.

Larvicides

Direct larviciding applies insecticide mixesto manure or other fly breeding sites. Larvi-ciding should be applied with high-volume,large-droplet equipment. Always use a coarsespray and high-volume mix. Consider this typeof application only where fly larvae are abun-dant and sanitation difficult. Chemical larvi-ciding also may be effective where biologicalcontrol has failed. Larviciding the whole dairyis never justifiable, and may reduce naturalcontrol, increasing the need for continuousinsecticide control.

Use larvicides carefully. Most kill benefi-cial insects as well as fly larvae. Apply themif you have a “hot spot” of heavy fly larvae,where they damage overall beneficial insectpopulations only slightly. Insect growth regu-lators such as methoprene (Altozid®) do notaffect most beneficial insects, controlling flylarvae only. However, methoprene may dam-age black soldier fly and rat-tailed maggotpopulations. Methoprene is the only larvicideregistered for use in dairies that does not in-jure predators and parasites.

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Feed-through or oral larvicides

Also available are feed and mineral larvi-cides, which can reduce fly breeding in ma-nure and feed waste. When fed, oral larvicidesprevent flies from developing in manure andspilled feed. They are ineffective against ex-isting adult flies.

For the feed additive to be effective, animalsmust consume the recommended dosage, and allanimals and manure must be treated. In areas withmany separate dairies located close to each other,all must use oral larvicides to control flies effec-tively. Flies may migrate from one herd to an-other within a few days, traveling across manymiles to any of dozens of dairies.

Larvicides are more effective against hornflies than for other flies. They do not controlhouse flies, stable flies, garbage flies or blow

flies completely because the flies develop inmany sites other than fresh manure, includingfeed mixing areas, silage holding areas andfeeding lanes.

Fly control with oral larvicides also requiresgood manure sanitation. Supplemental fly con-trol is always needed where flies breed in ma-nure from such untreated animals as indoorpenned calves.

The active ingredients in feed-through lar-vicides include tetrachlorvinphos (Rabon®),methoprene (Altozid®), and phenothiazine.Only tetrachlor-vinphos and methoprene havetolerances in lactating cattle. Rabon 7.76 per-cent oral larvicide is suggested to be fed at70 mg/100 pounds body weight. It comes inpremixes, mineral mixes or blocks, molassesblocks, or in custom feed blends.

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3. Use everything needed to get the job done. Apply deci-sive force at critical times and places to achieve your de-sired goal. Don’t scrimp on resources. Reluctant half-mea-sures work against you.

4. Attack weakness, not strength. Flies have three greatstrengths: a short generation time, a high reproductive rateand the ability to detoxify many poisons. It is almost use-less to attack the strengths head-on. IPM uses roundaboutmethods to gnaw at the strengths that allow fly populationsto build up to economically harmful levels.

To erode the flies’ strengths, dairy producers can:

• Increase generation time. The length of time it takes toproduce a new generation of flies depends on conditionsof the physical environment. Changing the environmentcan double and even triple the time that flies complete ageneration.

• Reduce reproductive rate. The physical environmentand amount of food available affect the flies’ reproduc-tive rate. Limiting available habitats and food can severelycut the fly reproduction.

• Manage resistance. Although flies rapidly become re-sistant to chemical control agents, resistance can be lim-ited through many management strategies, some of whichdo not kill flies or maggots. For instance, insect growthregulators (IGRs) affect larval development and alter gen-eration time and the number of individuals passing intothe adult stage. This strategy preserves a large propor-tion of insecticide-susceptible individuals in the popula-tion and reduces the number of resistant adults repro-ducing in a succeeding generation.

Principles of fly controlNine principles govern fly control in dairies. They also pro-

vide excellent guidelines in your IPM program.

1. Set a measurable and clearly defined goal. If progress isslower than expected, perhaps your goals are ill-defined.Planning is essential in any IPM fly-control program. Foreach goal, lay out a plan of action that:

• Includes a way to measure progress.

• Plans for prevention.

• Includes only mutually compatible methods, eliminat-ing those that counteract each other.

• Is simple and flexible to allow changes.

• Plans for setbacks.

2. Gain and maintain the initiative. Take action before prob-lems arise. Get ahead of the flies before they get ahead ofyou. Start control activities early, use multiple methods,and keep constant pressure on flies throughout the season:

• Begin control activities while flies are still dormant.

• Monitor fly populations and control results.

• Adjust fly-control practices to meet new situations.

• Avoid repeating actions that have failed.

• Add control practices to support previous actions.

• Continue control efforts until fly activity stops at the endof the season.

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LARVICIDES

Table 6. Larvicides for use on dairy fly larvae.

Rabon® 50WP - 4 lbs in 25 gal. water applied at1 gal. spray per 100 sq. ft. of manure. Repeat at7-10 day intervals.

D.z.n.® diazinon 50W - 4 lbs. in 25 gal. waterapplied at 1 gal. spray per 350-750 sq. ft.manure or debris.

Baits

Methomyl + tricosene (Golden Malrin) - Placewhere flies congregate away from feed, water,milking area. Apply where children, birds oranimals will not contact.

D.z.n. Diazinon 50 W.P./Sugar/Molasses -Mix 1/2 lb. 50% W.P. with 1.0 lb. sugar or 2 cupsof syrup or molasses and dissolve in 21/2 gal. ofwater. Treat around cracks, crevices, doorways,

windows and other areas where flies congre-gate; do not contaminate milk, feed, water orapply where animals may consume.

Ultra low volume (ULV) applications(nuisance flies)

Aerial: Dibrom® 14 concentrate (85%Naled)—Dilute 100-230 fl oz (3/4-1 3/4 gals)Dibrom concentrate in 100 gals. No. 2 fuel oilor diesel oil. This is equivalent to 0.1 to0.2 lbs. actual Dibrom per acre at 100 m.p.h.

Ground (Thermal Fog): Dibrom® concentrate(85% Naled) I—Dilute 1 gal. Dibrom to 99 gals.No. 2 fuel oil or diesel oil or 13 oz. Dibrom to10 gals. oil. Apply at 40 gal/hr. at ground speedof 5 m.p.h. with swath of 300-400 ft. wide.

Flies also have four great weaknesses: They are vulner-able to changes in habitat, changes in food supplies, com-petition from other species, and predators and parasites.These well-known weak points have been the founda-tion of fly control for centuries.

To attack weaknesses, dairy producers should:

• Change, limit or destroy larval habitats. Habitatchanges severely restrict fly development. The key issanitation. Take preventive actions to reduce the size ofavailable habitats. Spread and dry manure or store it asliquid until spreading. Maggots develop much moreslowly at very high or very low temperatures and whenthe growth medium is too dry or too wet. Slight changescan double and even triple generation times. As a result,far fewer individuals survive, and populations are moreexposed to natural control factors.

• Limit or destroy larval food supplies. Here, sanitationand feed commodity management are crucial. Make surethat livestock — not flies — get the feed. Keep com-modities, hay and bedding materials dry. Without foodor water, maggots die. Limit fly access to spilled feed,hay, silage and mixtures of feed and manure. This cutshe number of flies that live to maturity.

• Encourage fly competitors. Adult soldier fly larvae,rat-tailed maggots and dung beetles never bother live-stock or people. However, they alter the developmentmedium to favor their own kind. Fly competitors squeezeout flies by destroying the fly habitat and consumingavailable food. To encourage fly competitors, avoid con-taminating their environment. Prevent off-target pesticidedrift or runoff that can kill these valuable allies.

• Cultivate and conserve fly enemies. Birds, predatorybeetles, mites and other predators take an enormous tollon flies. Provide shelter and protection for predators. Con-serve parasites. Artificially increase parasite numbersthrough release programs. Limit pesticide use to areasthat do not shelter helpful animals. Avoid pesticide driftor runoff. When possible, use chemicals that do not harmnatural enemies. Use fly control practices that take ad-vantage of fly natural enemies.

5. Use only the material and effort necessary to achievethe desired result. Don’t waste time, energy or resourceson overkill.

6. Make all methods and actions work together. Remem-ber that you are in charge of your fly-control operation.Don’t let the flies or other factors distract you from yourgoal.

7. Continue to monitor fly populations throughout the sea-son. Don’t be surprised by a fly population explosion. Beflexible in your use of time and IPM methods. Give your-self some space to adjust to situations as they develop.

8. Do the unexpected. Take advantage of materials and prac-tices that flies have not experienced before. When flies re-sist a control agent or adapt to overcome a control practice,use new materials or different practices the flies have notrecently encountered.

9. Keep control efforts simple. The more complex the fly-control operation, the more there is to go wrong.

Certain states do not recommend the useof oral larvicides or insecticides given throughthe feed. Rabon® oral larvicide, methoprene(Moorman’s IGR), and phenothiazine feed ad-ditives often do not control flies unless usedextensively.

Resistance

A disadvantage of feeding tetrachlorvin-phos is resistance. Tetrachlorvinphos (Rabon®)is an organophosphate insecticide. When feed-ing Rabon® oral larvicide, flies are likely toresist other organophosphates.

This means that other insecticides in thisclass will be ineffective, including naled(Dibrom®), dimethoate (Cygon®, GoldenMalrin Liquid®), coumaphos (Co-Ral®),fenthion, diazinon, malathion and many oth-ers. Bear resistance in mind when planning touse tetrachlorvinphos oral larvicides.

Methoprene oral larvicides do not produceresistance. However, they injure several help-ful insects, including black soldier flies andrat-tailed maggots. Take precautions to keepmethoprene from destroying them. Whenfeeding oral larvicides, follow label direc-tions and precautions.

Scouting forbreeding sites

Only certain areas on the dairy may exceedthe nuisance or tolerance levels of flies. Scoutingis essential to find breeding sites and to decidewhere to apply additional sanitation and larvicidesand where to release parasites. Check breedingmedia for maggots and pupae in these locations:

• In poorly drained cattle guards wheremanure and feed accumulates.

• Inside calf hutches around bottom sideswhere manure and bedding remain wet.

• Outside the curbing of exit walkways andlanes where the curb meets the soil andwhere manure and feed wash over the curb.

• On feeding lanes where upright concretestalls meet drive-through lanes.

• Under open elevated feed bunks in hold-ing lots where undisturbed manure andfeed collect.

• In manure wash or flush canals awayfrom free stalls where manure gathersand remains wet.

• In settling basins collecting debris along-side; at entrances and exits from basins.

• On excess floating mats on edges of la-goons where anaerobic respiration hasdeclined.

• Around solid separators where manureaccumulates and remains undisturbed.

• Around the edges of manure piles thathave remained unmoved for 10 days.

• In entrances to silage pits where waterhas collected.

• On unwashed mechanical manurespreaders.

• At entrances and areas next to feed-hold-ing facilities where moisture and feedcollect.

• Along milk parlor exit lanes that collectmanure.

• Along water troughs where manure col-lects.

• Under fence lines where manure has notbeen removed by scraping.

• In sick-calf and -cow pens where manurebuilds up along sides of sheds or underfence lines.

• Around water leaks where feed and ma-nure may accumulate.

• Around feed-mixing facilities where feedspillage and moisture occur.

• Around bale feeders where manure andstraw accumulate.

For IPM to work effectively, each controlmethod must be timely, decisive and compat-ible with present and evolving dairy produc-tion practices. Once you have decided on astrategy, it is best not to switch to another.Adopting a course of action usually locks youinto a chain of related activities until the endof fly season. By following the decision makerin Figure 12, you can design your own indi-vidualized program and adopt a program thatbest fits your operation.

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Produced by AgriLife Communications, The Texas A&M University System

Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion,age or national origin.

Issued in furtherance of cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, andJune 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, Texas AgriLife ExtensionService, The Texas A&M University System.

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