Ask the Vet

By Dr. Ken McMillan
DTN/The Progressive Farmer Contributing Editor

Question:

I used Spalding's Fly Predators with success last season, with the exception of horn fly control. Can I use a product like Rabon and Fly Predators at the same time? If I use ivermectin, how often can I apply the topical solution? It would seem to me that ivermectin and Rabon would be more effective on horn flies and face flies. What do you think?

Answer:

Rabon, an oral larvacide, and insect growth regulators (IGRs) can be used with Fly Predators. Fly Predators, branded beneficial insects, lay eggs inside fly pupae, and their larvae feed on and kill developing flies. Maggots that have ingested sufficient IGR/Rabon never make it to the pupal stage, so Fly Predators never come into contact with them.

Topical applications of insecticides can be used if you are using Fly Predators, but with caution. Fly Predators are more susceptible to fogs and aerial sprays than the flies themselves. Pour-ons/sprays can be used away from areas where Fly Predators are spread.

I do not feel topical ivermectin applications should be looked at as fly control. Many experts feel repeated use of these products for fly control is driving resistance to this whole class of products. These products are too important for control of intestinal parasites to risk creating more resistance. Think of them as dewormers, and use them at the optimal time to control intestinal worms. Any control of external parasites, including flies, should be seen as an added benefit.

Good fly-control programs are based on an integrated pest-management (IPM) program. USDA defines IPM as "a sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health and environmental risks."

While I have never used Fly Predators or had much experience with them, I feel they could be a part of an IPM program. This concept is new to most livestock producers. Using them requires doing your homework and learning how they work and how they must be used. Be sure to follow all directions and ask questions if you are unsure of any aspect or are not getting the control you expect.

(VM/CZ)

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