How to Manage Pests
UC Pest Management Guidelines
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.
1 Three to four year rotations give satisfactory results. A rotation for fewer years will give some suppression.
UC IPM Pest Management Guidelines: Alfalfa