How to Manage Pests

Mosquitoes

Managing Mosquitoes on the Farm Section 5: Natural Waters Associated With Farms Published 2005 Sections of this publication:

Why You Should Care About Mosquito Control West Nile Virus You May Be Raising the Mosquito That Is Biting You! Mosquito Prevention Three Basic Principles of Mosquito Prevention Natural Waters Associated With Farms Managing Stagnant Waters Created by Agricultural Activities Irrigated Fields for Upland Crops Mosquito-Free Irrigated Pastures Rice Dairy Operations Biological and Chemical Mosquito Control Common Mosquitoes and Their Life Cycles Acknowledgments For More Information

Growers and dairy operators often serve as stewards of natural waters because ponds, streams, and other wetlands can occur on farmland. Natural waters support a variety of animals including ducks, fishes, amphibians, dragonflies, and fairy shrimp. Managing mosquitoes in extensive wetlands is beyond the scope of this publication (see Managing Mosquitoes in Surface-Flow Constructed Treatment Wetlands, (PDF* 373K), ANR Publication 8117). This section supplies a few principles of mosquito prevention that are useful in most natural waters.

Permanent, clean natural waters produce relatively few mosquitoes because these have good populations of predatory insects and/or fish. However, significant mosquito problems can occur in waters that are very weedy and shallow, especially if they receive fertilizers or manure. Therefore, such runoff should be prevented through proper irrigation drainage, conservative use of fertilizers, and creating buffer areas between fields and wetlands.

Unlike stagnant waters created by farming activities, it is undesirable and usually illegal to drain, fill, or substantially reconfigure natural wetlands, and some wetland vegetation is also protected. Private citizens may not introduce fish into natural waters. Changes can sometimes be made under state or federal permits. Consult your local MVCD about what changes are needed and permitted. Several kinds of alterations reduce mosquito problems. Weed control allows natural predators to hunt mosquito larvae more effectively. For example, thin rushes and cattails annually and remove old leaves. Shallow, temporary wetlands can be mowed when dry. If you have a stream on your property that forms isolated, stagnant pools, connect the pools to the main channel with small ditches. This allows predatory insects and fish to find and eat mosquitoes and can aid stream flow, which drowns mosquitoes.

Some coastal farms have tidal areas that produce mosquitoes when flooded by the tides or rain. Manage this problem by constructing and maintaining ditches that drain off the water when the tide falls. You may need to add a levee with a tide gate to reduce or prevent salt water from entering during high tide, while allowing fresh water to flow out at low tide. MVCDs may use insecticides to control marsh mosquitoes, but this can become costly in extensive areas of marsh. In such cases, physical control is preferable unless the presence of endangered species or other concerns prevent land reconfiguration.

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Managing Mosquitoes on the Farm, UC ANR Publication 8158 Sharon P. Lawler and Gregory C. Lanzaro, Department of Entomology, University of California, Davis

Copyright © 2005 The Regents of the University of California, Division of Agriculture and Natural Resources. All rights reserved.