How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

Several species of Empoasca leafhoppers occur in alfalfa. They all have the same general overall appearance: small (0.125 inch long), bright green, wedge-shaped bodies. Nymphs (immatures) also have green wedge-shaped bodies and run rapidly when disturbed. They may run forward, backward, or from side to side. Their curious movement plus their shape serve to distinguish them from lygus bug nymphs and slower moving aphids. Other green leafhoppers may be present in alfalfa, but they are much larger in size. Other small leafhoppers found in alfalfa are brown or gray in color and do no apparent damage.

DAMAGE

The most common damage symptom is a yellow, wedge-shaped area at the tip of the leaf. Frequently, the leaf margin and tissue surrounding this area turns red. This symptom may occasionally be confused with boron deficiency but can easily be distinguished from it by the presence of the insect. Plants may become stunted and have very short internodes. Stunting and yellowing may persist into the next cutting cycle, even in the absence of leafhoppers.

Although Empoasca leafhoppers may be found throughout the year, damage in the Central Valley is generally found during July, August, and occasionally September. In the Imperial Valley, damage may occur from May through September; infestations are often adjacent to or upwind from sugarbeets.

MANAGEMENT

Scheduling an early cutting can effectively manage damaging leafhopper populations, otherwise insecticide treatment may be warranted.

Cultural Control
If alfalfa is within a few days of harvest, early cutting will control Empoasca leafhoppers.

Organically Acceptable Methods
Cultural controls are acceptable for use on an organically certified crop.

Monitoring and Treatment Decisions
Check the field in July and August (and if necessary into September) to see if leafhoppers are present. At the first sign of injury, sample the field with a standard sweep net. Leafhopper infestations usually begin on the field margin so be sure to include field edges in your samples. For information on sweep sampling, see SAMPLING WITH A SWEEP NET.

Sample four areas over the entire field by taking 5 sweeps in each area and counting the number of adults and nymphs. Record observations on a monitoring form (100KB, PDF).

If alfalfa is 2 or more weeks away from harvest, apply treatments if counts reach five leafhoppers per sweep (adults and nymphs combined). Alfalfa scheduled to be harvested in 10 days to 2 weeks should be treated if counts reach 10 per sweep. Often, leafhopper infestations of treatable magnitude are confined to the first 50 to 100 feet of the field margin. If this is the case, treat only the field edges where high leafhopper counts are found.

As an alternative to treating the entire field, border cutting works well to "herd" the leafhoppers into the uncut strip. The strip can then be sprayed a few days after cutting, thus reducing the need to spray the entire field.

PUBLICATION

UC IPM Pest Management Guidelines: Alfalfa
UC ANR Publication 3430
Insects and Mites
C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
L. D. Godfrey, Entomology, UC Davis
M. Rethwisch, UC Cooperative Extension, Riverside County (Blythe)
D. R. Haviland, UC Cooperative Extension, Kern County
P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier
R. F. Long, UC Cooperative Extension, Yolo County

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