Side by side: mosquito control

07/14/2010 @ 11:00pm

Spring brings wet weather. And wet weather brings mosquitoes. Livestock bothered by mosquitoes spend more time scratching and less time eating. If attacked by mosquitoes, dairy cows produce less milk. Beef cattle, sheep, and poultry lose weight. In addition, mosquitoes can transmit deadly viruses, including West Nile and encephalitis.

Are those enough reasons to take preventive measures before mosquitoes become a problem on your farm and around your home this summer?

Water is key to the growth of mosquitoes. All young mosquitoes hatch and develop in water before they mature into flying insects. They breed in stagnant water, and thrive in weedy ponds and in water that collects in ditches, fields, or containers. It can take as few as four days for mosquitoes to mature when standing water is present.

Ponds, streams, and wetlands that are well managed and kept clean produce few mosquitoes. Typically, these natural waters have plenty of predatory insects or fish.

If the wet area becomes too weedy or the water too shallow, mosquito problems will occur.

According to Sharon Lawler and Gregory Lanzaro, Department of Entomology at the University of California-Davis, there are four basic principles of mosquito prevention.

1. Prevent or eliminate wastewater. Any water that stands for more than four days is a breeding ground. This includes water in ruts or containers not being used such as old tires and machinery. Properly drain areas so no surface water is left standing.

2. Keep weeds well trimmed around ponds and ditches. Weeds are the perfect hiding place for mosquitoes. Significant mosquito problems can occur in waters that are very weedy and shallow, especially if they receive runoff that includes fertilizers or manure. Prevent these problems by using fertilizers conservatively and by creating a buffer between fields and wetlands.

3. Irrigate properly so surface water is gone within four days.

4. Supplement preventive methods with biological and chemical control. Consider treating ponds with a biological larvicide (see chart) or introduce insect-eating fish (see sidebar). You can treat the water in livestock troughs with a biological larvicide. Mosquito fish can be added to control mosquitoes in tanks or troughs. Ten to 15 adult fish can provide quick control.

Pastures are often placed on shallow, poorly drained soils. To ensure pastures don't become a breeding ground for mosquitoes, consider implementing these practices: a. Grade land for irrigation and drainage before planting a forage crop. b. Wet soil just to depth of the roots. c. Irrigate only as needed. d. Drain excess water within 24 hours after irrigating. e. Inspect drainage and broken checks. f. Keep animals off soft soil. g. Rotate fields. Breaking up fields into smaller ones will allow you to rotate animals so fields can dry properly. h. Avoid overfertilizing.

Livestock management practices can also make a difference when it comes to controlling mosquitoes. If livestock drink from ponds and natural pools of water, their waste adds nutrients. This is food for mosquitoes.

In addition, if the area around the pond is soft, hoofprints can create puddles. Install a fence around the pond to keep livestock out. This will also prevent erosion of the bank.

The area around watering troughs can have the same problem. Animal hooves produce hundreds of small water pockets. Permanently correct this mosquito-breeding ground by providing drainage or paving around the trough.

Regularly clean cattle tanks and watering troughs. If drainage outside the trough is good, you can flush out the water every week, and this will help control mosquitoes. If tanks or troughs are not being used, remove them.

Look around your farm. Are there old tires that could be removed? Is that old, unused piece of machinery still sitting behind the shop? Is the tarp someone forgot to fold up and put away still outside next to the barn?

Each of these places is an ideal area to accumulate water and produce hundreds of mosquitoes. Check your farm on a regular basis to be sure no potential problem areas exist.





Trade name: VectoLex

Bacillus sphaericus or Bs is a naturally occurring bacterium. Bs spores eaten by mosquito larvae release toxins into the mosquito’s gut, causing the larvae to stop eating and die. It is only effective against actively feeding larvae. Pesticide products containing Bs remain active for one to four weeks after application.

Granules are mixed with water and other substances and sprayed from the air or the ground.

Trade names: Aquabac, Bactimos,
LarvX, Teknar, VectoBac

Bacillus thuringiensis israelensis or Bti is a naturally occurring soil bacterium to control mosquito larvae. The larvae eat the Bti product, which is made up of the dormant spore form of the bacterium and an associated pure toxin. The toxin disrupts the gut in the mosquito by binding to receptor cells.

Bti is available in liquid, granular, or briquette formulations and applied by hand (with a sprayer) or aerially.

Trade names: Altosid, Bayer Advanced Garden Mosquito Preventer, PreStrike, Zodiac Preventive Mosquito Control

Methropene is a compound that mimics the action of an insect growth-regulating hormone and prevents the normal maturation of insect larvae. It is applied to water to kill mosquito larvae. It may be used with other mosquito-control measures in pest management programs.

It can be applied as a liquid, pellets, or

Mineral oils
Trade names: Bonide, BVA2,
Golden Bear-1111 (GB-1111)

Oils, like films, are pesticides used to form a coating on the water’s surface to drown larvae, pupae, and emerging adult mosquitoes. They are specially derived from petroleum distillates and have been used for many years to kill aphids on crops and to control mosquitoes. They can be used with other mosquito-control methods.

It is available in liquid form and applied by
spraying methods.

Monomolecular film
Trade names: Agnique MMF, Arosurf

Monomolecular films are a nontoxic pesticide that forms a thin film on the surface of the water. The film makes it difficult for mosquito larvae, pupae, and emerging adults to attach to the water’s surface, which causes them to drown. Typically, films are active from 10 to 14 days on standing water.

It is available in liquid form and applied by
spraying methods.

Trade name: Abate

Temephos is an organophosphate (OP) pesticide. It is the only OP with larvicidal use. Temephos helps prevent mosquitoes from developing resistance to bacterial larvicides. It is used in areas of standing water and shallow ponds and can be used with other mosquito-control methods.

It is available in liquid or granular form.

The mosquito fish is a small top-feeding minnow that is often used to control mosquito larvae.