How to Manage Pests

UC Pest Management Guidelines

Alfalfa

Leafhoppers

Scientific Names:
Garden leafhopper: Empoasca solana
Potato leafhopper: E. fabae
Mexican leafhopper: E. mexara

(Reviewed 11/06, updated 4/08, corrected 9/10)

In this Guideline:


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 (100 KB, 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.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
The following materials are listed in order of usefulness, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. PERMETHRIN*
  (Pounce) 3.2EC 4–8 oz 12 see comments
  (Ambush) 25WP 3.2–12.8 oz 12 see comments
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Do not apply when bees are present. Do not apply more than 8 oz/acre/cutting of Pounce or 12.8 oz/acre/cutting of Ambush. For Pounce the preharvest interval is 0 days for 4 oz/acre and 14 days for more than 4 oz/acre; for Ambush it is 0 days for less than 6.4 oz/acre and 14 days for more than 6.4 oz/acre.
 
B. CARBARYL*
  (Sevin) XLR 1 qt 12 7
  (Sevin) 4F 1 qt 12 7
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: Do not use any carbaryl formulation when bees are present. For forage crops, do not apply more than once per cutting or exceed 1 qt/acre/cutting. For hay crops, do not exceed 3 pt/acre/cutting.
 
C. DIMETHOATE
  (Dimethoate 400) 0.5–1 pt 48 10
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
  COMMENTS: Check label to see if product allows only one application per year or per cutting. Do not apply when bees are present.
 
D. CHLORPYRIFOS*
  (Lorsban) 4EC 0.5–1 pt 24 7 (0.5 pt); 14 (1 pt)
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
  COMMENTS: Do not make more than 4 applications/year or apply more than once per crop cutting. Do not apply when bees are present. Avoid drift and tailwater runoff into surface waters.
 
E. ZETA-CYPERMETHRIN*
  (Mustang) 1.5EW 2.4–4.3 fl oz 24 see comments
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Do not apply more than 4.3 oz/acre/cutting or more than 12.9 oz/acre/season. Preharvest interval is 3 days for cutting and grazing and 7 days for seed.
 
F. METHOMYL*
  (Lannate) LV Label rates 48 see comments
  (Lannate) SP Label rates 48 see comments
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: Restricted entry interval: 48 hours. For Lannate LV the preharvest interval is 7 days for grazing, feeding and cutting; for Lannate SP it is 0 days for cutting and 7 days for grazing and feeding.
 
G. LAMBDA-CYHALOTHRIN*
  (Warrior) 1.92–3.2 fl oz 24 see comments
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Do not apply when bees are actively foraging. Do not apply more than 0.24 pt/acre/cutting or 0.96 pt/acre/season. Preharvest interval is 1 day for forage and 7 days for hay.
 
H. CYFLUTHRIN*
  (Baythroid) 2E 0.8–1.6 fl oz 12 7
  (Renounce) 20WP 1–2 fl oz 12 7
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Do not apply to alfalfa grown for seed because of potential for injury to bees. Baythroid: do not apply more than 2.8 fl oz/acre/cutting or more than 11.2 fl oz/acre/season. Renounce: do not apply more than 4 oz/acre/cutting or more than 16 oz/acre/season.
 
**   See label for dilution rates.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment until the field can be grazed or cut. In some cases the R.E.I. exceeds the P.H.I.; the longer of these two intervals is the minimum time that must elapse before harvest may take place.
* Permit required from county agricultural commissioner for purchase or use.
1 Modes of action are important in preventing the development of resistance to pesticides. Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode of action is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

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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