How to Manage Pests

Mosquitoes

Managing Mosquitoes on the Farm Section 8: Mosquito-Free Irrigated Pastures 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

Irrigated pastures often create an environment favorable for mosquitoes, especially floodwater mosquitoes. Pastures are often put on shallow, poorly drained soils, or on heavy basin soils that normally occur where the land is relatively flat and difficult to drain. Many irrigated pasture plants are shallow rooted and require frequent irrigations. Because pasture drainage is often poor, take care to prevent pastures from becoming a source of mosquitoes. Luckily, the same practices that are likely to increase the production of pasture feed also help eliminate mosquitoes.

• Have the land properly graded for irrigation and drainage before planting the forage crop. Without proper grading, irrigations may be less effective and mosquito problems are more likely.
• Apply only enough water to wet the soil to the depth of rooting. Otherwise, nutrients will be leached from the soil, water will be wasted, and standing water will be more likely.
• Irrigate only as frequently as is needed to maintain proper soil moisture. Check soil moisture regularly until you know how your pasture behaves.
• Drain excess water from the pasture within 24 hours following each irrigation. This prevents scalding and reduces the number of weeds in the pasture. Good check slopes are needed to achieve drainage. A drainage ditch can remove the water from the lower end.
• Inspect fields for drainage and broken checks periodically to see whether releveling or reconstruction of levees is needed. Small areas that hold water can be filled and replanted by hand. Broken checks create cross-leakage that provide habitat for mosquitoes.
• Keep animals off the pasture while the soil is soft. An ideal mosquito habitat is created in irrigated pastures when water collects in hoofprints of livestock that were run on wet fields or left in the field during irrigation. Keeping animals off wet fields until soils stiffen also protects the roots of the forage crop and prevents soil compaction that interferes with plant growth.
• Rotate fields. Break up your pasture into a number of smaller fields so that the animals can be rotated from one field to another. This allows fields to dry between irrigations and provides a sufficient growth period between grazings. It also prevents hoof damage, increases production from irrigated pastures, and helps improve water penetration into the soil by promoting a better root system.
• Do not overfertilize. Excess fertilizers can leach into irrigation tailwater, making mosquito production more likely in ditches or further downstream.

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.