A gallon of water can produce 10,000 mosquitoes in a summer
By CAROL RYAN DUMAS
Mosquitoes are opportunistic when it comes to procreating, laying eggs in any pool of water available, but farmers can control them with some simple measures.
It just takes knowing what environment is conducive to egg laying and hatching and eliminating it, said Kirk Tubbs, manager of the Twin Falls County Pest Abatement District.
How to irrigate and avoid raising a crop that bites back was the topic of Tubbs' presentation at the Agri Action 2013 farm show in Twin Falls.
Mosquito larvae require shallow, standing water to hatch, and the more putrid, the better, because the larvae feed on organic matter in the water. They can hatch on the outer edges of ponds, in marshy areas, wet pastures, cattail stands, junk tires, water troughs, buckets, tarps, and even hoof prints and tire impressions in the dirt, he said.
A gallon of water can produce 10,000 mosquitoes over the summer. And while people like to blame water sources such as rivers and lakes, most mosquitoes travel less than half a mile, he said.
"So if you're really getting eaten up, look close," he said.
It takes as little as seven days for standing water to produce mosquitoes. The most effective way of reducing mosquito populations is to control the larvae, which are confined and easy to exterminate, he said.
People often get excited about adult mosquitoes flying around, but by that time, they're behind the curve where control is concerned, he said.
Mosquitoes aren't just annoying, they can also carry disease, such as West Nile virus, he said.
There are several things farmers can do on their property to prevent mosquitoes from laying eggs and larvae from surviving, he said.
First, any containers should be emptied of water where possible. Old rimless tires holding down tarps should be stripped of the sidewalls, and all tarps with puddles of water should be drained.
Pastures should be allowed to dry out between watering cycles so any indentations in the soil do not become mosquito breeding grounds, and irrigation systems should be checked for leaks.
Ditches, canals and ponds should be as free of leaves and debris as possible. Vegetation in and around waterways and ponds can be mowed or burned when they are dry. Not only does that decrease organic matter in the water but it also eliminates the protective areas when the larvae develop into pupae and climb out of the water to dry their wings before they can fly, he said.
Ponds can be constructed to have a steep drop-off from the bank so there's no shallow edge along the rim. Ponds can also be rock cobbled, which is poor habitat for larvae.
Many mosquito-breeding conditions can't be remedied or avoided, but there are good options for controlling the larvae, Tubbs said.
Small fish that feed on the larvae can be introduced into ponds where possible. Goldfish in water troughs also do a good job of keeping mosquitoes under control, he said.
In addition, adult mosquitoes can smell fish and typically won't lay eggs in water that contains fish, he said.
Bubblers can be placed in ponds to keep the water moving, but it usually isn't effective on the outer edges.
Effective, natural bacterial treatments also exist.
Studies suggest that applying larvacide to 1,000 acres is the equivalent of adult control on 72,000 acres, he said.
Another product addresses mosquitoes in the pupal stage and is used to cover water surfaces with an alcohol-based film. The film changes the water tension so the pupae can't float and have to keep returning to the surface for oxygen until they tire and die.
The prime time to treat for mosquitoes is in May and June before the larvae hatch.
Twin Falls County Pest Abatement District: www.tfcpad.org