Young calves are often the first to fall victim to mosquitoes. (Texas A&M AgriLife Extension Service picture by Dr. Joe Paschal)
Young calves, such as these pictured in Aransas County, are often the first to fall victim to mosquitoes.

Improper mosquito control on livestock can do more harm than good

Important chemical label specifically defines how product should and can be used.

In an effort to save their livestock from torment from the plague of mosquitoes in the wake of Hurricane Harvey, some producers in Texas and the Southeast are making the mistake of misusing chemicals to control the pests, Texas A&M AgriLife Extension livestock entomologist Dr. Sonja Swiger said.

“The results can be potentially disastrous,” Swiger warned. “Misuse of potent chemicals can quickly become an example of ‘the cure is worse than the malady’ not only for the animals being treated but also to the environment.

“I have heard people promoting the use of premise treatment products for mosquito control on their cattle,” she said. “They’re reportedly using pyrethroid chemicals that are labeled ‘NOT FOR USE ON ANIMALS’ on their cattle. I can’t emphasize enough how important it is to follow the label, even if it’s 10 pages long. What a tragedy it could be if producers whose animals survived the storm lost them through their own wrongdoing.”

Dr. Joe Paschal, AgriLife Extension livestock specialist in Corpus Christi, Texas, added that he also has heard some reports of off-label pesticide use in the affected area.

“One recommendation was a product I had not heard of,” he said. “I looked it up, and it turned out to be a termiticide, which, of course, was not approved for livestock -- only premises.”

Swiger said the all-important chemical label specifically defines how a product should and can be used.

“Products that are labeled ‘not for animal use’ are not at the proper application rate for the animals or -- worse -- shouldn’t be used on animals at all,” she said. “Applying them to livestock could have a negative impact on the animals such as skin issues, (chemical) retention in the meat or even death.”

There are products available that are labeled for on-animal use. Most are permethrins or other pyrethroids, but the labeling will say specifically how to treat the animals, she said.

Swiger conceded that the current demand and logistical problems following Hurricane Harvey have made livestock pesticides harder to find than normal, but they are available.

“In a disaster situation, people might feel using anything is better than using nothing, but this is, of course, not a smart idea. If the products are not on hand, then make the effort to get the right products,” she emphasized.

Still, Swiger said if producers do nothing, that does not help suppress the mosquito populations feeding on the cattle, which could also be detrimental.

“Most older cows can withstand the extensive bites and large numbers reported, but they should not have to,” she said. “Calves and heifers are more susceptible and can suffer from anemia due to blood loss or even asphyxiation due to the large mosquito populations. Keep in mind that one female mosquito can lay an average of 200 eggs, and at least half will be female. All will emerge at one time, so there could be hundreds to thousands of mosquitoes looking for blood at the same time. Since these mosquitoes grow in uninhabited locations most of the time, cattle and wildlife are their first hosts.”

Paschal said, when confronted by massive numbers of the pests, the main immediate problems are inhaling and ingesting mosquitoes, especially by young calves.

“Hard as it is to believe, under normal circumstances, asphyxiation — choking and death — can and does occur following events such as Hurricane Harvey,” Paschal said. “Besides the hazards to young calves that have already been pretty well stressed from the storm, mosquitoes can transmit parasites and diseases to other animals — such as heartworms to dogs, the encephalopathies and equine infectious anemia to equines and, of course, numerous human maladies."

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