How to Manage Pests

UC Pest Management Guidelines

Alfalfa

Biological Control

(Reviewed 11/06, updated 11/06)

In this Guideline:

Alfalfa is an important reservoir for natural enemies of insect pests. These natural enemy populations often develop in alfalfa fields and expand into other plantings such as cotton, melons, and beans.

Several species of predaceous bugs are found in alfalfa including assassin bugs, bigeyed bugs, damsel bugs and minute pirate bugs. Other predators found in alfalfa are lady beetles, collops beetles, lacewings, syrphid flies, and spiders. These predators feed on a variety of pests such as alfalfa weevil larvae, aphids, alfalfa caterpillars, beet armyworm, western yellowstriped armyworm, webworms, leafhoppers, and three-cornered alfalfa hopper.

Several species of parasitic wasps are found in alfalfa: Hyposoter exigua is a parasite of beet armyworm and western yellowstriped armyworm, Cotesia (Apanteles) medicaginis is a parasite of alfalfa caterpillars, and Trichogramma spp. are egg parasites of various caterpillar pests. Parasitic wasps that attack aphids in alfalfa include Aphidius spp., Diaeretiella spp., and Lysiphlebus spp. Bathyplectes curculionis is an important parasite of the alfalfa weevil. Do not treat alfalfa with insecticides until the economic treatment level for a specific pest has been reached and the predator and parasite populations have been assessed for their potential role in controlling the pest. Insecticides often destroy beneficial insects, leading to severe secondary pest outbreaks. See the table of relative toxicities of insecticides and miticides to find out which pesticides are most compatible with natural enemies.

Birds are important predators of insect pests in desert alfalfa. Egrets, ibis, and gulls feed on crickets, cutworms, and other insects forced to move at the leading edge of flood irrigation water. Blackbirds eat alfalfa weevil larvae, aphids, cutworms, and other insect pests.

NATURAL ENEMIES AND THEIR COMMON PREY IN ALFALFA

PUBLICATION

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430

General Information

• C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
• P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier

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