Integrated Pest Management: A Systems-Approach to Insect Pest Control

During the years following World War II, many synthetic pesticides became available for agricultural uses, including insecticides for controlling cattle pests. Relatively easy to use and inexpensive, insecticides initially provided rapid and effective control of a wide variety of troublesome insects. However, concern grew over the unintended consequences of pesticide use, such as toxicity to plants, fish and wildlife –even other insects and organisms that were natural enemies to targeted pests. And, of course, there was concern over potential impacts to human health, should surface and ground water become contaminated.

Consequently, further use of some pesticides was prohibited or severely limited. Remaining and newly developed “safer” formulations have not been without limitations either. There is the cost factor, since most pesticides are petroleum derivatives and cost of production is tied to that of oil. Particularly perturbing to producers has been increasing resistance, among targeted pests, to available pesticides. Despite greater frequency of their use and increased dosages, or because of those tactics, some naturally resistant individual pests survive and pass on the resistance trait to offspring. With each successive generation, pest populations become more difficult to control.

Hence, to reduce reliance on pes-ticides and still optimize their efficacy, agricultural producers, including managers of cattle operations, are encouraged to implement Integrated Pest Manage-ment (IPM). Accord-ing to Texas AgriLife Livestock/Veterinary Entomologist Sonja Swiger, IPM represents a systems approach to insect pest control.

“IPM incorporates multiple, least-risk op-tions for controlling populations of troublesome pests, and limits impact on other organisms and the environment,” explains Swiger. “For cattle operations, IPM may incorporate cultural, biological, and chemical controls.”

Controlling pests with integrated management

Cultural controls, says Swiger, involve monitoring and managing an operation to minimize the occurrence of pests. On cattle operations, it means stepping up sanitation efforts, particularly with regard to insect breeding grounds. Manure management is key for feedlots and diaries, but attention should also be given to feed storage areas and refuse piles – any areas where the combination of organic material, warmth, and moisture are conducive to insect breeding and larval development. In a ranch setting targets include corrals, working areas, and lots where cattle may be held in concentrated numbers.

“Biological controls utilize what nature has provided – living organisms which function as parasites, predators, or pathogens to help control pests,” says Swiger. “Certain insects – dung beetles and others that breed in manure – compete with species of flies that also breed in that environment. Some predatory insects feed on fly larvae. Others, like parasitoid wasps, seek fly pupae in which to lay their eggs.

”Some cattle feeding operations and dairies introduce populations of these nat-ural enemies to help control flies, making this form of biological control a standard procedure in their IPM plan.

“To help promote biocontrol, pesticides should be used judiciously. Wherever possible, chemicals that are the least toxic to natural enemies should be chosen,” adds Swiger.

Another biological factor that breeding herd managers might consider is genetic resistance among cattle. Some animals appear to have greater natural resistance to pests – a desirable trait for genetic selection and one which geneticists are pursuing through DNA-marker selection.

“While the objective of IPM is to minimize use of pes-ticides, using alternative controls to reduce pest populations, there are situations where chemical control measures are nec-essary to keep pests from causing significant economic loss,” states Swiger. “Chemical controls may be the only answer when population thresholds are reached and insect pests take their economic toll.”

Why pesticides for fly control

Flies rank among the most troublesome pests on most cattle operations, and deserve particular consideration when developing an IPM program. Collectively, flies cause blood loss, contribute to the spread of disease, and serve as a torment to cattle. Aggravation and resulting stress are responsible for the lion’s share of losses.

Studies suggest that heavy fly infestations can rob 20 pounds from end-of-summer calf weights, and cause weight loss among nursing cows. Research suggests average daily gain among summer-grazed yearling steers may be reduced by as much as 15 percent. Generally, speaking, horn flies and face flies have the greatest economic impact. Losses result from reduced cattle performance coupled with the expense of trying to reduce populations that reach and exceed threshold levels.

“We’re talking big numbers. Flies reduce profits at the U.S. producer level by over $1 billion annually,” says Montana State University Entomologist Greg Johnson. “Most of that can be attributed to horn flies, but face flies and stable flies cause significant losses too.

”Blood-sucking horn flies breed in fresh manure but spend nearly all of their adult lives on cattle, taking 20 to 30 meals each day. The economic threshold level is estimated at 200 horn flies per animal.Face flies also breed in manure. They don’t bite, but feed on eye secretions of cattle, causing irritation and weeping which attracts more of their kind. Face flies are also blamed for spreading bacteria that cause pinkeye. The economic threshold is 10 face flies per animal.

Face flies also breed in manure. They don’t bite, but feed on eye secretions of cattle, causing irritation and weeping which attracts more of their kind. Face flies are also blamed for spreading bacteria that cause pinkeye. The economic threshold is 10 face flies per animal.Horn flies and face flies typically plague cattle on pasture, though some reports indicate stable flies are becoming more common in pasture situations. Typically, however, stable flies are most numerous in feeding areas and nearby hay storage sites. Moist hay or straw provide a favored breeding environment for stable flies. They are blood feeders and 10 to 12 flies per animal is the economic threshold.

Waging war on fliesAccording to Johnson, producers do have a varied arsenal of chemical weapons for waging war on flies. A number of pesticide formulations and delivery methods are available and there is no single “best” plan of attack.“The insecticide ear tag has been popular for cattle on pasture. They’re certainly the most convenient. If you can put them in at the start of the fly season, and they work, you shouldn’t have to worry about flies for the rest of the summer,” says Johnson.

Typically, the tags are impregnated with either a pyrethroid or organo-phosphate insecticide, or a combina-tion of both. Johnson says producers report better results when using tags with different chemistry in alternate years. Using tags with the same class of insecticide in successive years appears to promote resistance.

Furthermore, fly tags should be removed from cattle as soon as the effective period of use has elapsed. Continued exposure to low, non-lethal levels of insecticide remaining in the tags can contribute to fly resistance problems.

Time of insecticide tag applica-tion may also affect fly control results. Producers that calve early in the spring may be ready to work calves in April, but that may not be the best time to apply fly tags.

“On northern ranges, like Mon-tana, flies seldom become a problem until at least a month, maybe two months later,” Johnson explains. “And the tags are only effective for about five months, so the efficacy of tags applied early could be spent before the fly season ends. Producers who put tags in when it is most convenient probably won’t get much late-season fly control.”

Another option, he says, is topical application of an insecticide, using a backrub. A variety of application devices are available commercially. Still popular, however, is the home-made rub fashioned from a length of heavy chain wrapped in burlap and suspend-ed between two big posts. Another type of topical applicator is the dust bag which dispenses insecticide dust when cattle come in contact.

Johnson says rubs and dust bags can provide 75 to 80 percent control of flies and that’s adequate. They do require maintenance. Rubs and dust bags have to be checked routinely and recharged. Bulls can be hard on them too, making repair or replacement necessary.

“Backrubs and dust bags work if cattle use them, but some cattle won’t unless they’re forced,” notes Johnson. “The best way might be to hang the rub or dust bag where cattle can’t avoid contact with it, like in the entry to a fenced area around a water tank.”

Another alternative is to apply insecticide to cattle as a spray or through a pour-on formulation. The advantage is knowing the cattle received treatment. Johnson calls topical formulations effective, but short-lived. Repeated applications generally are required for lasting fly control, and that means repeated gathering and handling of cattle which may induce some stress.

It should be noted that topical application of insecticide products, and especially pour-on formulations, are often used for control of lice and ticks. Producers should be reminded that effective control of lice requires two applications. The first kills adult lice only, and a second application two weeks later is needed to kill lice that hatched from eggs that were present on the animal’s hide but unaffected by the initial insecticide treatment. Some insecticide tags also provide control of lice and ticks.

Still another method of fly control involves the use of a feed-through larvacide or insect growth regulator (IGR) administered to cattle through a feed supplement. Johnson says these products do exactly what they’re supposed to do, passing through the animal and killing or preventing development of larvae that hatch in manure. They work well, as long as each animal consumes the required amount.

Producers have to decide what will be cost effective for their individual operations, in terms of time, labor, cost of products, and expected results. Veterinarians can help develop insect control programs tailored to specific operations, advises Johnson.

“Unfortunately, there are limited cultural and biological controls for some of the insect pests that challenge beef cattle operations, particularly in pasture situations,” adds Swiger. “So IPM, for many cattle managers, must focus on strategic use of insecticides – using them only when really needed, rotating classes of insecticide from year to year, and always following the manufacturers’ directions.’