NDSU Extension - Morton County


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June 15, 2020 Fly Control

Renae Gress, Extension Agent/Agriculture and Natural Resources


Dates to Remember:

  • June 17: Cover Crops and Prevent Plant Online Café Talk, 7:30am
  • June 17: Container Gardening Presentation-Online, 7pm
  • June 18: In depth perspective of Steer and Heifer Complex, 7pm
  • June 23: Your Money Your Goals Online-Behind on Bills, 3pm
  • June 30: My First Business: Online Babysitting Class


Fly Control

I think everyone can agree that flies are annoying little buggers. The constant buzzing sound, how they manage to get in everything and their ability to easily dodge our attempts to swat them are all unpleasant. Not only are they an annoyance to humans but they are a greater nuisance to livestock. Flies can cause pain, aggravation, stress, pinkeye, reduce weigh gain and reduce milk production. 

Horn flies, face flies and stable flies are the three main types of flies livestock have to deal with. Horn flies are gray and look like small houseflies. They generally are located near the head, shoulder and back of the animal but can also be found on their belly. These flies are blood sucking and can feed up to 30 times per day. Their life cycle is 10-20 days and peak population occurs in midsummer and early fall. Face flies look like large dark houseflies. They are nonbiting and feed on animal secretions. These flies live around 21 days and achieve peak population in late summer. Stable flies are similar in size to houseflies and have circular markings. They generally are found on the abdomen and legs feeding on blood. Their life cycle is 10-24 days and are often present at pasture turnout.

So what should you do if your livestock have flies?

Well first, you need to monitor the fly population and identify the economic threshold. Count the number of flies on the head, back and shoulders of at least 15 animals. If 100 of more flies are counted on average, producers should implement control measures.  Generally the economic threshold has been reached when the fly count reaches 200 flies per animal which will lead to significant weight loss.

There are a few options on controlling flies in pasture and they include:

  • Ear tags containing insecticides: These slowly release insecticide into the animal’s hair. They shouldn’t be applied until near economic threshold around mid-June to July. Be sure to remove the tags when they no longer provide control to prevent flies from becoming resistant.
  • Pour-ons and sprays: Should be applied periodically depending on environmental conditions.
  • Self-application devices including back rubbers and dusters and nonchemical traps: These can provide limited control if cattle can use them when they choose.
  • Feed additives insecticides: Can be included in mineral formations. Offer at least 30 days prior to fly emergency in late June or early July

It is important to rotate the class of insecticides you use each year. Always remember to follow the label and use the method of control that fits best with your operation. Although pest control can be costly, following IPM principles and applying the appropriate product, at the appropriate time, for the appropriate control of pest populations will keep your cattle healthy and leave more money in your pocketbook.

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