NC State Extension

Pest Problems After Storms – Flies on Farms

Chicken standing in water-logged litter

Chicken standing in water-logged litter

Hurricanes & similar storms can leave behind some additional problems for livestock and poultry producers by damaging poultry and hog houses, horse barns and other livestock structures. The first concern, of course, will be to care for the animals and repair damage as soon as possible. However, fly numbers are likely to rise dramatically around poultry houses and other dry waste systems such as horse barns and cattle lots in the wake of a hurricane. Confinement hog houses and some layer operations with liquid waste handling systems should not experience severe fly outbreaks unless they are unable to flush wastes into the lagoons for a week or more. Poultry houses (broilers, breeders, turkeys) that have lost any portion of their roof are particularly vulnerable. Wind blown rain will  wet large areas of litter and/or manure, even if a building’s roof remains intact, especially where side curtains or end doors have been damaged by the storm. Rain soaked feed spills from destroyed feed bins are another concern, as are storm related disruptions of carcass disposal. The mix of organic matter + moisture + warm temperatures will produce a large spike in fly populations within 10 days.

Reducing the likelihood of a storm-related fly outbreak on the farm is problematic
at best — there are likely to be more pressing issues. Nevertheless,
here are some guidelines that may help:
  1. Remove and dispose of wet litter/manure/feed/etc. as soon as possible. Obviously, this will not be practical or even possible in many cases. Wet litter/bedding can be replaced with fresh shavings/straw where removal is possible. Dispose of wet material by land application or composting if local conditions will allow it. Additional dry material (shavings or chopped straw) may be required to make a drier mixture for successful composting.

  2. For small areas, mix wet litter/bedding with hydrated lime to absorb excess moisture. Top dress with several inches of fresh shavings, straw or other bedding material. For large areas, wet litter/manure/bedding
    can be mixed with equal or greater amounts of fresh bedding/litter.
  3. Increase airflow as much as possible over wet areas to evaporate excess moisture. Continuous, high volume air flow will be most effective.

  4. Flies collecting on the outside walls of a poultry building.

    Flies collecting on the outside walls of a poultry building.

    Be prepared to apply insecticides to manage fly outbreaks. Baits will not be effective due to the large amount of available organic material. Permethrin
    and RaVap® will be most effective as surface sprays on interior building
    walls. Use products containing a pyrethroid such as cyfluthrin or lambda cyhalothrin products on interior surfaces when animals and birds can be removed, as well as for exterior treatments. Do not treat interior walls if animals are present unless the product label allows it. These chemicals will provide good fly control for a minimum of 10-14 days. Apply spot treatments to eliminate concentrations of maggots where there are isolated areas of wet material. Use broadcast treatments only when most or all of the manure, litter or bedding area has been saturated. RaVap®, Rabon® or dimethoate are effective spot treatment insecticides for maggot control. Space sprays (fogs) with pyrethins, PBO-synergized permethrin, or other approved insecticides can be used effectively for rapid knockdown of adult flies. Check the North Carolina Agricultural Chemicals Manual for additional information.

  5. For waste stockpiles:
    • Be sure that drainage carries standing water away
    • Cover with black plastic to aid solar heating and shed rainfall. Finally, here’s a caution about land application of wastes as a method of disposal. Be careful about where the material is spread. Avoid land application within a mile or two of residences if at all possible
    • Understand that wet litter and manure will likely contain a large
      number of fly larvae and pupae. It’s true that only a small
      percentage will survive and successfully emerge as adult flies,
      but those survivors can create a fly nuisance even when the waste is thoroughly incorporated. Application and incorporation will destroy all but 1% to 5% of the fly larvae and pupae, but even this relatively small percentage can produce thousands of flies if the manure/litter/bedding is heavily infested.

For more information:

Written By

Photo of Dr. Michael WaldvogelDr. Michael WaldvogelExtension Specialist (Household & Structural Entomology) (919) 515-8881 mike_waldvogel@ncsu.eduEntomology and Plant Pathology - NC State University

Contributing Specialist

Photo of Dr. Wes WatsonDr. Wes WatsonInterim Head, Professor and Extension Specialist (Livestock & Poultry) (919) 513-2028 wes_watson@ncsu.eduEntomology and Plant Pathology - NC State University
Page Last Updated: 2 years ago
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