Spring brings wet weather. Wet weather brings mosquitoes. Livestock bothered by mosquitoes spend more time scratching and less time eating. If attacked by mosquitoes, horses, 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 around your acreage this summer?
The most effective method for controlling mosquitoes is targeting them at the larval stage. By reducing the areas mosquitoes may breed, you make it less likely they can mature into the adult stage.
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 they 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.
Four basic principles
According to Sharon Lawler and Gregory Lanzaro, department of entomology at the University of California-Davis, there are four basic principles of mosquito prevention.
- Prevent or eliminate wastewater. Any water that stands for more than four days is a breeding ground. This includes water in ruts or containers, such as plant saucers, birdbaths, and flat roofs. Properly drain areas so no surface water is left standing. Empty and change the water in birdbaths, fountains, wading pools, and rain barrels at least once a week.
- 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 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.
- Irrigate properly so surface water is gone within four days.
- Supplement preventive methods with biological and chemical control. Consider treating ponds with a biological larvicide (see chart, bottom of page) or introduce insect-eating fish, such as the mosquito fish (see sidebar, below). The water in livestock troughs can be treated with a biological larvicide.
Once applied, larvicides can last for a few weeks. Be sure to follow the manufacturer's application directions on the label. Mosquito fish can also be added to a birdbath to control mosquitoes.
If you have animals on your acreage, livestock management practices can make a difference when it comes to controlling mosquitoes. Livestock that drink from ponds and natural pools of water add nutrients to the water through their waste. 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.
Pastures are often placed on shallow, poorly-drained soils. To ensure pastures don't become a breeding ground for mosquitoes, consider implementing these practices:
Grade land for irrigation and drainage before planting a forage crop.
Wet soil just to depth of the roots.
Irrigate only as needed.
Drain excess water within 24 hours after irrigating.
Inspect drainage and broken checks.
Keep animals off soft soil.
Rotate fields. Breaking up fields into smaller ones will allow you to rotate animals so fields can dry properly.
Take a look around
Rain gutters are another area that can accumulate water. Inspect gutters on a regular basis to minimize debris buildup and water collection.
Whatever method you decide to use to control mosquitoes, be sure it's cost effective and environmentally safe. Consider alternatives before applying a conventional chemical insecticide.
Look around your acreage. Are there old tires that could be removed? Are containers inverted so they don't accumulate water? These are ideal areas to accumulate water and produce hundreds of mosquitoes. Check your acreage regularly to be sure no potential problem areas exist.
This minnow can help kill mosquito larvae
There are a variety of ways to reduce and eliminate mosquito larvae before they hatch. But did you know certain predators, such as mosquito fish, can help control larvae?
The mosquito fish (Gambusia affinis) is a small surface-feeding minnow that is an efficient predator of mosquito larvae. The full-grown females are usually less than 21⁄2 inches in length, while males are typically under 11⁄2 inches.
The muted silver and light olive green body color is common to both sexes. In addition, they are able to lighten or darken their body color pigmentation to closely match their surroundings.
Rapid reproduction cycle
Mosquito fish are ovoviviparous. This means eggs hatch within the female's body, and the fry (recently hatched or juvenile fish) are delivered as free-swimming, independent young. The gestation period varies from 18 days to 35-plus days.
Each female can produce three to four broods per year. Brood sizes range from approximately 25 to 100. Several broods of young may be produced from a single fertilization and are delivered during warm seasons in temperate climates.
Water temperature is very important to the growth and reproduction of this fish. Its preferred temperatures are between 77°F. and 86°F.
Stocking rates vary depending on the habitat. For ponds, the general stocking rate is a minimum of 0.1 pounds of fish (about 20 fish) per surface acre as they reproduce quickly. For season-long control, fish should be stocked in early spring. However, they shouldn't be introduced in a pond unless it is man-made and isolated from natural waters.
Contact your local mosquito and/or vector control technician to evaluate your acreage before stocking any fish.
Trade name: VectoLex
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
|It can be appliedas a liquid, pellets, or briquettes.|
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.|
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 conventional 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.|
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Photographs: PunchStock, Virginia Fish and Wildlife Information Service
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