Fly control strategies for dairy calves and heifers

Fly control is critically important on all livestock farms.  Flies negatively impact dairy calves in two primary ways:

The key with any fly management strategy is to start early in the season before fly populations become a problem.  A simple but useful way to monitor the fly population on your farm is to place at least 10 3-by-5-inch index cards throughout your operation.  Take corrective action if more than 10 fly spots (black dots) occur on any one card during a 24-hour period.  It is important to develop an integrated pest management plan to maximize fly control on your operation.

The first step is maintaining sanitation within the calf’s environment.  Flies reproduce in undisturbed, damp organic matter.  Minimize the amount of wet bedding, wasted hay, and manure near calves and heifers.  Remove and dispose of wasted feed daily.  Consider alternative bedding.  Some calf growers will switch to sand bedding during the summer.  Sand is inorganic and does not support the growth of flies.

Work toward building your whole program around source reduction through prevention and debris management.  Scout for maggots to see where flies originate and then target debris management tactics accordingly.

Soiled bedding under confined calves and heifers is likely to be the principal source of house flies and stable flies. Organic debris left over from winter is a big hazard and should be dispersed by May 1 (and probably earlier the farther south you are).

Spilled hay, TMR, and silage, if wet, will be fly sources too.  Organic debris older than two weeks in summer will have been around long enough to produce new adult flies.  So, if scrape-and-haul is an option, do it every-other week and replace with fresh bedding. Haul to spread or to active compost, not just cold stack. Flies will easily disperse a half mile, so simply stacking soiled bedding in a corner of the property will not be adequate.  Eliminate weeds and tall, unwanted vegetation around facilities to reduce attractiveness to flies.

Next, consider feeding an insect growth regulator.   An insect growth regulator (IGR) is a feed additive that can be added to milk or milk replacer (either during milk replacer manufacturing or as an add-pack).  It may also be added in calf starter grain.  An IGR should be added to the feed several weeks before the start of fly-season so that manure in calf housing contains IGR if and when flies begin reproducing.

ClariFly® larvicide aids in controlling house flies and stable flies in confinement-housed dairy cattle.  ClariFly works by disrupting development of the fly’s exoskeleton (external skeleton) in immature flies, killing them so they do not become adult flies.  The recommended dosage of ClariFly is 0.10 mg per kg of live bodyweight per animal per day.  Start feeding Clarifly early in the spring, 30 days before flies begin to appear, and continue feeding throughout summer and into the fall until cold weather restricts fly activity.  To minimize the number of over-wintering pupae, feed Clarifly 30 days past the first frost.

Other items to consider in an integrated pest management plan include premise insecticide sprays, fly control tape and traps, pour-on fly control insecticides, fly bait poisons, and fly parasitoids.  With a fly control strategy in place, your calves can have less exposure to disease and more energy for health and performance.

Contact your consultant to discuss fly control strategies for your dairy operation.