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How to Manage Pests

UC Pest Management Guidelines

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Alfalfa

Crop Rotation

(Reviewed 11/06, updated 11/06)

In this Guideline:

Avoid planting alfalfa directly into a field from which an alfalfa crop was recently removed. Rotation to a nonhost crop can significantly reduce pest populations in the field. The table below provides information on nonhost crops that suppress alfalfa-associated nematode and pathogen populations. Also included are a list of crops in which herbicides that are not registered for use in alfalfa can be used to manage weeds.

If your field is infested with stem nematode or pathogens listed in the key below, consider choosing a nonhost crop from the table. Although 3- to 4-year nonhost crop rotations are ideal, they are not commonly practiced. A rotation of lesser duration is still beneficial but to a lesser degree.

For winter weed control, choose a wheat or oat crop rotation and an herbicide treatment. Manage summer weeds by growing a corn rotation and using selective herbicides and cultivations. For fall plantings, rotate to another crop to manage established weeds such as nutsedge, bermudagrass, or burclover because they are not effectively controlled with herbicides used in conventional alfalfa.

Volunteer alfalfa around the field edges of a rotation crop may perpetuate nematode populations. If your field has a history of nematodes, be sure to remove all volunteer alfalfa.

Pest Rotation information
Root knot nematode 1 year rotation with cotton.
Stem nematode 3-4 year rotation with small grains, beans, cotton, corn, sorghum, lettuce, carrots, tomatoes, or forage grasses1.
Diseases: 3-4 year rotation with small grains, beans, corn, sorghum, forage grasses1.
Winter weeds A minimum of 1 year (preferably longer) in crops such as small grains, wheat, oats, winter forage grasses that allow the use of selective herbicides that are not registered in alfalfa.
Summer weeds A minimum of 1 year (preferably longer) in crops such as small grains, beans, cotton, corn, sorghum, summer forage grasses that allow the use of selective herbicides that are not registered in alfalfa.
Special weeds
At least 2 years with cotton or other nonhost crops such as small grains, beans, corn, sorghum, or forage grasses. Avoid rotations with crops such as tomatoes, onions, and carrots that also serve as a host for this weed.

Two year rotationwith corn or sorghum rotation that includes application of herbicide to control nutsedge.

1 Three to four year rotations give satisfactory results. A rotation for fewer years will give some suppression.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430
General Information
P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier

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