Fly control in confined livestock and poultry production operations

By Ralph E. Williams, entomologist, Purdue University

Fly Control in Confined Livestock Operations

Of flies occurring in livestock confinement operations, including feedlots, dairies, swine, and sheep, of most concern are stable flies, Stomoxys calcitrans, and house flies, Musca domestica.  Control of these two flies follows similar techniques.

Surveillance/Diagnosis:  Both stable flies and house flies can cause annoyance to livestock.  Stable flies feeding on livestock, especially on the legs, causes foot stomping, tail swishing, animal bunching, and nervousness.  Excessive house fly populations can also alter animal behavior.  Animals become reluctant to feed with high numbers of house flies present around feeders, and animals often bunch together to avoid fly activity.  Observing animal behavior can be an indication for the need for fly control.

Monitoring fly activity can be accomplished in several ways.  The use of light traps, baited fly traps, sticky ribbons, and spot (fly speck) cards are useful in monitoring fly activity, especially house flies inside buildings.  Electric fly traps, preferably those that either stun flies or simply get them stuck on a sticky pad, can be used in areas accessible to electrical outlets.  There are several commercial light traps available that can be used.  These should be placed away from competitive light sources, and be accessible for changing the sticky pads in them.  Flies stuck on sticky pads in these devices can be counted.

Baited fly traps can either be purchased or made.  Commercial traps usually consist of a jug design with liquid contents and fly attractant.  Traps can be made using gallon plastic milk jugs with four 5 cm holes cut in the upper part of the sides.  Place a small amount of granular fly bait (1 oz) into the jug.  The holes allow flies to enter the jug to feed on the bait and die.  Baited traps can be suspended with wire from rafters or building support beams.

Sticky fly ribbons can be strategically placed in a facility as well.  Place these where fly activity is likely and in a position where they hang vertically with both sides exposed.

Fly spot cards consist of 3” by 5” plain white file cards that can be attached to obvious fly resting surfaces.  When flies land on these cards they usually leave fecal and regurgitation spots.

The number of light or baited traps, sticky ribbons, or spot cards needed will vary according to the building size and configuration.  Five to 10 units of any of these minimally should be used.  These devices should be checked, serviced or replaced at 7 day intervals and fly activity enumerated.  Numbers of flies caught or fly specks counted will vary by facility but a general rule of thumb is if 250 flies are caught per week per unit, or 100+ fly specks are counted per card, this would normally indicate higher fly activity that needs attention.  Fly spot cards can be saved to provide historical documentation of fly activity and control effectiveness.

Outdoors, baited traps can be used as well as sticky traps.  Sticky traps can be commercially obtained or made.  One type of commercial trap that has shown to be effective in monitoring both house fly and stable fly activity is the Olson Fly Trap.  This is a cylindrical trap placed on a wood stake and wrapped with a sticky sleeve (see www.olsonproducts.com).  Like indoor monitoring devices these outdoor traps should be serviced on a weekly basis.  Stable flies can be monitored directly by counting flies on the legs of animals, the preferred feeding location for these biting flies.  A minimum of 10 to 15 animals should be included and flies observed on all four legs counted.  Fly control is generally warranted when counts average 5+ flies per leg.

Another aspect of monitoring for fly activity is to identify sites where flies are breeding in and around the operation facilities.  Designing a map/guide of the operation layout showing buildings, feeders, loafing areas, watering sources, hay feeding areas, walkways, etc. will be useful in the monitoring activity.

Create a checklist of sites to monitor and keep this as part of a written fly management plan, along with adult fly activity records.  This checklist can be used to assess the need for breeding site cleanup and maintenance and for fly control action steps needed.

Potential fly breeding area to check include:

  • Areas under fences and perimeter edges and corners of loafing areas
  • Under and around feeders, waterers, and water tanks
  • Old feed in bunkers and spilled along edges
  • Moist piles of manure and bedding
  • Loading areas for manure hauling and application equipment
  • Alley ways and animal loading areas
  • Silage effluent at the base of silage piles or spilled silage
  • Around the base of silos
  • Around and beneath stored and fed hay bales
  • Spilled feed around feed mixing areas and augers
  • Calf pens and hutches, particularly in corners and around feed and water sources
  • In and around sick animal pens
  • In and around maternity pens
  • Runoff areas
  • Vegetation surrounding pens

Fly Control:  Effective control of stable flies and house flies in livestock confinement operations involves an integrated approach.  Sanitation is the first and most important step to prevent fly development.  No insecticide can be effective for these flies as long as breeding sites exist.

Sanitation/Cultural:  Proper waste management and sanitation practices is a key aspect of an effective fly control program.  Livestock confinement facilities should be properly designed or modified to facilitate the ease in cleaning of waste and minimize accumulations of manure, spilled feed, moisture, and other sources of organic debris.

Confinement operations vary significantly in size and management practices.  The following points are recommended sanitation and cultural practices that should be considered for incorporating in an integrated fly pest management program to fit in with any given type of operation:

  • Scrape and clean loafing areas frequently
  • Clean stanchions and gutters frequently
  • Clean up spilled feed weekly
  • Divert surface water by grading and providing drainage around barns and facilities
  • Enclose area under feeders and provide concrete aprons around feed bunkers and waterers
  • Maintain working float valves in water tanks to prevent overflows
  • Provide shelters over feed bunkers to prevent excessive moisture from rain and feed wastage
  • Provide curbs and concrete surfaces in loafing areas to aid cleaning
  • Clean out maternity stalls and hutches frequently
  • Move calf hutches at frequent intervals
  • Flush manure pits under slatted floors at frequent intervals to remove solid waste buildup
  • Minimize seepage from silage storage by covering and sealing edges of bagged silage and silage piles
  • Clean around the base of silos and auger runs at frequent intervals
  • Cover and store hay bales on dry land or raised pallets, or store hay in properly designed stacks or hay sheds
  • Screen windows and maintain closed entries into milking parlors and processing areas
  • Keep lagoons free of debris and floating solids and do not overload
  • In feedlots:

-                maintain mounds to provide a dry area for animals and drainage for excess moisture to escape

-                maintain good slopes in pens to provide good drainage

-                drainage systems should be maintained with enough slope to move the moisture to holding ponds during wet periods

-                scrape wet areas to facilitate drying

-                stock pens with enough animals to cause effective trampling of wastes

  • Keep weeds and grass cut around the perimeter of pens and buildings to minimize fly resting areas and allow for effective wind movement
  • If manure is used as fertilizer and spread directly on farm agricultural fields, spread the manure thin enough for rapid drying

Biological Control:  Several insectaries have available parasitic wasps that can aid in fly control.  Depending on the climate and geographic location, some species of these wasps are more effective than others in reducing fly numbers.  The most effective species utilized are in the wasp family Pteromalidae and in the genera Muscidifurax and Spanlagia.  These are fly pupa parasites in which the female wasp oviposits one or more eggs inside a fly puparium.  The larval wasp kills the developing fly and emerges from the dead fly puparium as an adult wasp.  Natural populations of these parasites exist but usually do not develop in high enough numbers to provide noticeable fly control.  Commercial release of these fly parasites can aid in the control of flies.  It is advised to check with commercial suppliers of these parasites to customize a suitable program eared for a particular operation.

In using these fly parasites for most effective fly control benefit the following conditions should be met:

  • Proper sanitation and cultural practices must be carried out.  Parasite releases complement these practices but cannot replace them.
  • When insecticidal treatment is necessary for supplementing fly control, only use insecticides and application methods compatible with parasite use.  Non-residual space sprays and fly baits, if applied properly, usually are safe to use.

Research studies have looked at other candidate biological control agents.  Recently, a fungus, Beauveria bassiana, has shown promise as a fly control agent.  This fungus works by attacking the cuticle of flies leading to their death.  Approved formulations of this fungus are currently being marketed for use in poultry operations.

Chemical Control:  In using chemical insecticides it is imperative to read and follow all label directions and restrictions.  While some insecticides may be used associated with beef, hog, and sheep operations, they may have use restrictions with dairy operations.

The following guidelines should be taken into consideration when choosing appropriate insecticides to use:

  • Read and follow all label direction for proper mixing instructions, application rates, and precautions.
  • Do not use insecticides for dairy cattle or dairy premise use if not labeled for such use.
  • Label directions may restrict use to nonlactating dairy cattle and not be allowed for lactating animals.
  • Do not contaminate milk, feed, or water when using an insecticide.
  • Keep insecticides in original containers properly labeled and in locked storage.
  • It is illegal to use an insecticide in any manner inconsistent with the label.

The use of insecticides are a viable part of an integrated fly pest management program.  They can be used for fly control in several ways.  Application methods include space (area) sprays, residual sprays, baits, on animal sprays, baits, larvicides, and oral treatments.

Space Sprays:  Space sprays are designed to provide a quick knockdown of active adult flies in an infested area without residual activity.  They can be applied using various spray equipment that delivers fine mists, aerosols, or fogs.  They are most feasible in portable equipment that can be walked or driven through a facility or operation (e.g. backpack, cart mounted, or truck mounted).  In large outdoor operations properly equipped aircraft can also be used.  Because these sprays do not provide residual control they should be used when adult flies are most active.  Chemicals registered for use include synergized natural pyrethrins, some pyrethroids, and dichlorvos.

Residual Sprays:  Residual insecticide sprays are applied to fly resting surfaces such as on walls, and support posts.  These sprays can be applied with hand sprayers or power equipment.  Sprays are normally applied onto a suitable surface to the point of runoff.  Avoid contamination of feed or water.  Classes of chemicals registered for use as residual sprays include some pyrethroids, organophosphates, and spinosad.  With formulations available, residual spray treatments will last from 7 to 10 days.  The development of genetic fly resistance between any of the classes of insecticides can be deterred by periodic rotation between these different groups of insecticides.  If residual sprays are not effective for use in a particular situation, they should not be used.

Animal Sprays:  Insecticide sprays on animals can be made, but should only be considered to provide temporary relief of sable fly adults.  This is not a feasible approach to control house flies, however.  Natural pyrethrins and some pyrethroids are registered for on animal use.

Fly Baits:  Insecticide fly baits are only effective against non-biting flies, primarily house flies.  Blood feeding flies like stable flies are not attracted to baits.  Most bait products available are in granular form and contain such active ingredients as methomyl, imidacloprid, and spinosad.  Baits should only be applied in locations inaccessible to animals.  They can be placed in bait stations, used as scatter baits in infested areas, or mixed with water to form a slurry (if allowed on the label) and applied with a brush on fly infested surfaces.  Baits are best used in buildings and enclosed areas and are less effective in outdoor areas.

Larvicides:  A number of insecticides are registered for use as larvicides.  They can be used directly on manure and other fly breeding sources.  This type of application is best utilized when reserved for treatment of lfy breeding spots not eliminated by normal sanitation practices.  Because of the chemical and physical makeup of manure and other decomposing material most larvicide treatments breakdown rapidly.

Oral Larvicides:  Oral larvicdes are available as controlled release boluses and feed additives for use with cattle.  Boluses, when ingested, stay in the reticulum and release insecticide over several weeks that passes out in the manure.  With feed additives in mineral supplements or block form the insecticide passes through the digestive system of the animal and is present in the manure to kill fly larvae.  Insecticides available include IGR’s and stirofos.  The problem with oral insecticide use is that only the manure from animals given the product is treated.  Only house flies breed in manure.  Stable flies prefer breeding sources containing decomposing plant material.  Also, house flies will also breed in other material besides fresh manure.  Oral larvicides are most effective where fresh manure is the primary fly breeding source.

Fly Control In Poultry Operations

Accumulated poultry manure can be highly suitable for fly breeding, especially where general sanitation is poor and when there is excessive moisture.  Suitable fly-breeding conditions can be present the year round in enclosed high-rise egg layer houses with long-term manure accumulation and in shallow pit houses in which manure is held for several months.  In other types of poultry operations (e.g. breeder flocks, broiler/turkey grow-out houses) flies may also be of concern.  In breeder houses with slatted floors flies can find breeding spots, especially under feeders and waterers, and wherever manure accumulations under the slats have high enough moisture content.  In broiler and grow-out houses for chickens and turkeys, little or no fly breeding usually occurs because the entire floor is covered with relatively dry litter.  Some fly breeding may occur in wet litter around the waterers, but this is usually a minor problem.

The house fly is considered the major pest fly species associated with poultry manure, especially in caged-layer operations.  House flies are the primary cause of public health nuisance complaints in surrounding communities resulting in poor community relations and threats of litigation.  The effective house fly dispersal range from their preferred breeding sources is from ½ to 2 miles with nuisance populations highest closest to their breeding source.  Of public health concern, house flies are capable of harboring more than 100 human and animal disease-causing organisms.

When little house flies (Fannia sp.) are present, high populations can develop on poultry farms.  Little house flies are less tolerant of hot, midsummer temperatures than house flies, and often emerge in large numbers in early spring, declining in midsummer, and peaking again in late fall.  Although these flies may invade nearby residential areas, they tend to be less annoying in that they do not readily settle on food or people.  Adult males show a distinctive aimless hovering or circling flight behavior of long duration within the poultry house or at outside shaded areas.  Females are less active and more often found near breeding sites.

Several species of blow flies may occur in poultry facilities.  They breed in decaying animal carcasses, dead birds, broken eggs, and wet garbage.  Large numbers can be produced in a poultry operation if there are larger accumulations of broken eggs and if dead birds are not properly and frequently removed.  Prompt removal of dead birds and rodents, preventing accumulation of broken eggs, and daily cleanup of processing areas is usually sufficient to prevent the build-up of these flies.

Small dung flies, along with several other small gnats, readily breed in poultry manure and other decaying materials.  They can occur in large numbers in poultry operations but generally are not a nuisance on the farm or in nearby communities.  Population levels are often higher in spring and late summer and fall.

Surveillance:  A standardized, quantitative method for monitoring fly populations should be a part of a poultry fly pest management program for use in making control decisions and to monitor control effectiveness.  Visual observations of fly populations alone are subjective.  Of sampling methods available, the use of spot/speck cards and/or sticky fly ribbons are the most widely accepted.

Fly spot or speck cards consist of 3 inch x 5 inch white file cards placed in a poultry house upstairs in high-rise or shallow pit caged layer operations and/or in the manure pit.  They can be suspended from strings or fastened to support posts, ceilings, or other areas where flies tend to settle (where there are larger numbers of fly fecal and regurgitation spots).  Placement is also best where there is little air movement and where workers or equipment will not disturb the cards.  Several cards can be placed in a facility, with date of placement and location noted on the card.  Once placed, cards should be left for a period of 7 days and replaced with new cards at the same place each week.  The number of “fly specks” on the exposed side (one side) of each card should be counted and recorded in a record keeping notebook or spreadsheet.  Generally, 100 or more fly specks per card indicates the need for fly control measures.  The use of spot cards is a simple, cost-effective, and widely adapted method for assessing fly populations week after week.  It also provides documentation of fly activity over the course of time and the effectiveness of control efforts that can be helpful in resolving conflicts with neighbors over claims of increased fly activity.

Sticky fly ribbons/tapes are another means of monitoring fly activity in a facility.  One method to use them is to select locations to hang them up for weekly intervals.  However, used this way, they often tend to dry and get dirty over time and become less effective in capturing flies.  A more suitable way to use them is to take a fresh tape, hold it out in front at waist level, and walk at a steady pace the length of house down one walkway between cages and back another walkway.  Flies caught on the tape can then be counted and recorded.  One to two fly tapes should be used per house at least once a week.  Generally, 100 or more flies caught per tape indicates the need for fly control measures.

Fly Control:  Four basic management strategies make up a successful integrated fly control program: cultural/physical, biological, mechanical, and chemical control.

Cultural/Physical Control:  Management of poultry manure so that it is not conducive to fly breeding is the most effective means of control.  Fresh poultry  manure generally contains 60 to 80 percent moisture.  Flies can readily breed in manure with a moisture content of 50 to 85 percent.  Manure moisture below 50 percent is less suitable for fly breeding, and fly breeding usually does not occur at 30 percent moisture or less.

Dry manure management is practiced under two types of systems: 1) frequent manure removal (at least weekly), and 2) long-term, in-house storage of manure.  Frequent manure removal systems to prevent fly breeding are based upon weekly (or more frequent) removal and field spreading it or transporting it to a holding area/composting site for drying/composting.  This can be effective if done regularly and thoroughly, but it does require adequate and available agricultural land where manure can be spread or suitable facilities for holding manure or for composting.  With belt manure removal systems belts need to remove manure two to three times per week.  Fresh manure on belts is attractive for fly egg laying activity and fly maggots can develop if manure is not removed quick enough.  These developing flies may then continue developing in manure storage sites once the belt removes the manure.  With in-house storage of manure, efforts should be made to reduce manure moisture below 50 percent (preferably to about 30 percent or less) and to maintain this level.

In either system, any practice that limits moisture in the droppings or aids rapid drying is helpful.  A few practices to follow include:

  • Prevent leaks in waterers.  Inspect the pit daily to check for leaks, and repair them when found.
  • When the water table is high or there is a danger of water running in from the outside, adjust the floor/grade relationship so that the floor of the house is higher than the surrounding ground and water runs away from the building.
  • Provide abundant ventilation both in the manure pit for effective drying and in the house for bird comfort.
  • Avoid rations that are laxative.
  • Use absorbent litter where practical.
  • Maintain proper insulation on water lines to prevent condensation.

Adequate ventilation reduces manure moisture and maintains desirable air temperatures, removes gases such as ammonia, and provides fresh air.  Exhaust fans located in the manure pit walls provide ventilation for environmentally controlled high-rise houses.  Also, supplemental drying fans (three-blade, 36-inch, direct-drive fans) installed between manure piles in the pits will greatly increase manure drying, especially that of the fresh dropped manure on the top of coned manure.  These supplemental fans should be installed about every 50 feet, positioned in the same direction in each row and reversed in position every other row to get maximum efficiency of air movement through the pit and manure surface.  These fans should be kept free of obstructions and run during daylight hours when birds are most actively producing droppings.

In facilities designed for in-house storage of manure, accumulated droppings, if left undisturbed with adequate ventilation and free of additional moisture, will form a cone-shaped mound under the cages and allow for natural composting.

Undisturbed manure accumulations normally support large populations of beneficial parasites and predators of breeding flies.  These parasite/predator populations primarily consist of predaceous beetles, mites, and parasitic wasps.  The buildup of these natural fly enemies is usually slower than that of flies.  Populations high enough to substantially benefit fly control can develop only if the manure is not disturbed for relatively long periods of time.  To encourage parasites and predators:

  • Maintain dry manure
  • Remove manure in cooler months when flies are less active.
  • Stagger manure removal over a few weeks to preserve beneficial parasite/predator populations.
  • Minimize the use of insecticides in the manure pit/storage area.

In-house composting of accumulating manure is a practice that can be established to   process manure and manage insect populations in high-rise layer houses.  This process involves agitating the manure to incorporate oxygen and possibly a carbon source to aid in the composting process.  This agitation results in increased temperature, an increased ammonia level, and decreased moisture content, all of which help reduce insect populations and makes the manure more valuable as a fertilizer source that is easier to handle when removed.  The agitation can be accomplished either by installing in-house chain- or tract-driven turning machines or by hydraulic-powered portable manure turners that can be used in multiple houses.  Turning the manure pile twice a week is usually adequate, but the best way to determine need is to take the manure pile temperature with a compost thermometer.  The temperature should be at least 120°F before turning is implemented.  Because this composting activity produces ammonia that is released in higher concentrations during the turning process, protective respiratory devices should be used by workers.  Also, composting eliminates beneficial parasite/predator populations, so ceasing to compost after being initiated can cause large house fly outbreaks.  Also, because most available composting equipment cannot continually turn high manure piles, the pit needs to be cleaned out when composted manure piles approaches 2 feet in height for most available equipment.

When manure needs to be removed from a facility, it is best to do so in cooler months when flies are less active and when cooler outside condition would minimize insect migration from field applied manure.  Also, fresh manure that accumulates within just 2 days after house cleanout is ideal for fly breeding, often resulting in a severe fly outbreak to occur 2 to 3 weeks after a cleanout.  When fly populations are low and less active during cooler weather this fresh manure will be less prone to a quick establishment of fly breeding activity.

During spring and summer, when fly and beetle dispersal is a major concern, manure that must be removed can be treated with an insecticide approved for such use to kill insects in the manure at the time of removal.  Manure can also be piled in a field before spreading and either treated again and/or tarped to kill developing insects.  Heat that develops in the manure pile under secure tarps will kill insects that are present.  After about 2 weeks under the tarp, the manure can be spread on fields without concern for pest dispersal.

Additional sanitation practices are also important in fly control.  Remove dead birds daily and dispose of them properly.  Minimize accumulation of spilled feed and broken eggs that attract flies and pest beetles.  On the outside, keep grass and weeds adjacent to poultry houses mowed to eliminate resting areas for adult flies and to allow for adequate air movement around the buildings.

Biological Control:  As indicated above, cultural/manure management practices encourage the survival and buildup of beneficial predators and parasites that can suppress house fly populations.  Keeping manure dry also encourages the increase in other insects that compete for nutrients in the manure habitat.

Such beneficial organisms as predacious mite (e.g. Macroceles sp.) and small black hister beetles (Carcinops pumilo) will readily feed on house fly eggs and first-instar house fly larvae.  Another group of beneficial insects are tiny parasitic wasps (primarily in the family Pteromalidae).  Female wasps oviposit their eggs in fly pupae.  Inside the fly pupa, the developing larval wasp kills and consumes the fly before it emerges.

With proper dry manure management predaceous mite and hister beetle populations often build up in higher numbers.  Parasitic wasps (often called “parasitoids”) usually occur naturally in lower numbers.  Control using these parasitoids is sometimes based on mass releases of commercially reared parasitoids.  Parasitoids are currently available from several commercial insectaries.  For a release program to be successful, the producer needs to consider which parasitoid species are best suited for their particular operations and in what numbers to release them and when.  Check with the suppliers of these parasitoids for recommendations.

Other insects, such as the darkling beetle (lesser mealworm, Alphitobius diaperinus) and dermestid beetles, often build up in high numbers under dry manure management.  They can be beneficial in competing for the nutrients in the manure and prevent house fly buildup.  However, they are responsible for damaging poultry structures (wood and insulation), harboring poultry disease organisms, and often being the cause of nuisance complaints when manure is transported and field applied when higher beetle populations are present in the manure.

A newer biological control agent has been developed commercially for fly control in poultry houses.  A natural pathogenic fungus Beauveria bassiana has been formulated into a spray product (balEnce).  This product is sprayed directly over accumulated manure.  Adult house flies, as they emerge from their pupal cases, come in contact with spores of Beauveria.  Spores released from the conidia develop hyphae which penetrate into the body cavity of the flies resulting in death.  Beauveria fungus has no detrimental effect on beneficial insects including histerid beetles and pteromalid parasitoid wasps.

Mechanical Control:  Screens and fly traps are two methods of mechanical fly control, if used properly.  Where possible, doors and windows should be screened to prevent entry of flies, especially in processing areas.  Several kinds of fly traps are available.  Some traps consist of a fly attractant in a liquid to attract flies, while others are electrical, employing a black light with either an electrically charged grid to kill the insects or are equipped with sticky sheets to get attracted flies stuck.  Traps do appear to be helpful in tight, enclosed areas where good sanitation practices are followed.  However, in areas of heavy fly populations, traps are not effective in reducing fly numbers to satisfactory levels.  They are best used as a supplement to other fly control procedures.  Jug fly traps containing a liquid attractant can be strategically located around the outside perimeter of poultry buildings to help reduce adult flies near buildings.  All fly traps need to be properly serviced and maintained to assure their optimal performance.

Chemical Control:  Insecticides should be considered as supplementary to sanitation and management measures aimed at preventing fly breeding.  Producers should monitor fly populations on a regular basis to evaluate their fly management program and to decide when insecticide applications are needed.  Chemical insecticides can play an important role in an integrated fly control program.  However, improper timing and indiscriminate insecticide use can lead to increased fly populations.  Also, selective application of insecticides can avoid killing beneficial fly predators and parasites.  Insecticide applications may be directed to adult flies (adulticides) or fly larvae (larvicides).  Methods of application include sprays (knockdown, residual), baits, and feed additives.

Knockdown, non-residual space sprays, mists and fogs are designed for quick knockdown and kill of flies with no residual action.  They are usually the most effective and economical method to control potentially heavy populations of adult flies.  Because they do have very little residual activity, resistance to the insecticides recommended as space sprays is low, especially when using products containing synergized natural pyrethrins.  Several pyrethroids are also available for use as quick knockdown sprays.  There are many machines on the market designed to produce the small particle spray size desired for this type of application (e.g. backpack sprayers, cart mounted sprayers).

Space spray application should be made to the point of “filling” a room or area with the spray mist.  Treatments should be made as frequently as needed to keep fly numbers down below identified nuisance levels.  This method of fly control is best used in the cooler, early morning hours when flies are resting higher up in the house and ventilation fans can be safely turned off during the time of spraying without causing increased house temperatures.  These insecticides should not be routinely applied in the pits of high-rise egglayer houses since they will kill beneficial insect populations present.

Treating building surfaces with residual sprays has been a common practice over the years.  Dependence on this method has led to high levels of fly resistance to the available insecticides used as residual sprays (e.g. pyrethroids, organophosphates).  Also, treated surface tend to quickly get covered over with dust, and this could reduce fly exposure on the treated surface.  Residual sprays should be used sparingly and only as a last resort to control fly outbreaks that cannot be managed with other techniques.

Fly baits are a viable part of an integrated fly control program to maintain low fly populations.   They are a very effective supplement to sprays.  Commercial dry baits in granular and extruded form are readily available.  They contain such active ingredients as methomyl Golden Malrin), imidicloprid (QuickBayt), and spinosad (Elector).  Bait placement should be on walkways/aisles and other areas where flies congregate.  Avoid application in the manure pit, since the available baits will kill beneficial parasite and predator populations.  Baits must also be placed out of reach of birds and placed so they don’t contaminate food and water sources.  Some bait/insecticide products are also available on hanging strips.  One such product, containing nithiazine (QuikStrike), has shown to be very effective and fast acting when properly placed in active fly areas.  Also, some bait products are available as brush on formulations or can be mixed with water to make a brushable slurry.  Apply these treatments on surfaces where flies tend to congregate.  Rotating the use of different bait products and active ingredients once or twice during a fly season will minimize the onset of fly resistance to any one active ingredient.

Direct application of chemical larvicides to the manure surface to kill fly maggots should be avoided, except for spot treatment or manure that is scheduled to be removed.  This is especially so with products (e.g. pyrethroids, organophosphates) that will kill beneficial insects inhabiting the manure.  Cyromazine and pyridine spot treatments of small areas with higher numbers of maggots can be effective and yet have a minimal effect on the beneficial insect population and potential fly resistance development in the manure.

Cyromazine (Larvadex) is the only feed-through insecticide for breeding flies registered for caged layers.  It is an insect growth inhibitor and kills fly larvae before development is completed.  Its selective mode of action does not adversely affect natural fly predators.  Larvadex premix is blended in to the egg layer ration at the rate of 1 pound of premix per ton of feed for fly control.  It passes through the bird’s digestive tract and is present in the manure essentially in its unaltered state.  It has no adverse effect on feed palatability or consumption, or on eggs or meat.

Larvadex will give best results when integrated into a well-managed fly control program.  Use of this product too frequently can be expensive.  Also, where it has been used extensively, high levels of fly resistance have been reported.  It is best to use Larvadex after a complete manure cleanout.  After cleanout, it can be fed to the birds continuously for 4 to 6 weeks.  Its use after that should be avoided until the next cleanout.  This will reduce the chance of development of fly resistance.  If adult flies should become a problem during its use or after the time it is used, then proper adult fly control measures should be carried out.

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