How to Manage Pests

UC Pest Management Guidelines

Alfalfa

Threecornered Alfalfa Hopper

Scientific Name: Spissistilus festinus

(Reviewed 11/06, updated 11/06)

In this Guideline:


DESCRIPTION OF THE PEST

The threecornered alfalfa hopper is a green, wedge-shaped insect with clear wings. The body, which is about 0.25 inch long, is higher and wider at the head end than and tapers towards the posterior. This insect gets its name from the hardened triangular (three cornered) area over the thoracic area as seen from above. It has piercing-sucking mouthparts. Nymphs are grayish white and soft bodied, with a line of saw-toothed spines on their backs.

Adults feed on numerous plants, including alfalfa. In alfalfa, nymphs are confined to the lower portions of the plant. Threecornered alfalfa hoppers can be found year-round. In the low desert, there are two population peaks for adults: one in late July/early August and a larger second peak in September/early October. In the San Joaquin Valley, threecornered alfalfa hoppers numbers usually peak in late September and October.

DAMAGE

Adults and nymphs of the alfalfa hopper feed by inserting their mouthparts into stems and sucking out juices. Injury is also caused when adult female hoppers insert their eggs into stems. Feeding and egg laying can girdle stems, causing the portion of the plant above the girdle to turn red, purple or yellow.

MANAGEMENT

Monitoring and treatment guidelines have not been developed, and there are no known parasites or predators effecting populations of this insect in California. Monitoring guidelines for sweep net sampling are difficult to develop because of the different alfalfa production systems and because the nymphs are concentrated on the plant at or near the soil line and not readily picked up by sweep nets.

This pest is not likely to cause severe damage in the San Joaquin Valley because it appears so late in the season, and treatment is rarely necessary.

In the Imperial Valley, damage is occasionally severe enough to justify control measures.

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. CYFLUTHRIN*
  (Baythroid 2) 1.6-2.8 fl oz 12 7
  (Renounce 20WP) 2-3.5 oz 12 7
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Do not apply to alfalfa grown for seed because of the potential for injury to bees. Baythroid: Do not apply more than 0.044 lb a.i./acre/cutting or more than 0.175 lb a.i./acre/season. Do not make more than 4 applications per year. Renounce: Do not apply more than 0.05 lb a.i./acre/cutting or more than 0.2 lb a.i./acre/season.
 
B. LAMBDA CYHALOTHRIN*
  (Warrior) 1.92-3.2 fl oz 24 1-forage; 7-hay
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Apply only to fields planted to pure stands of alfalfa. Do not apply when bees are actively foraging. Do not apply more than 0.24 pt (0.03 lb a.i.)/acre/cutting or exceed 0.96 pt/acre/year.
 
C. METHOMYL*
  (Lannate LV) 1.5 pt 48 0
  (Lannate SP) 0.5 lb 48 0
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: Restricted entry interval: 48 hours. Do not graze or feed livestock for 7 days after application. Do not apply when bees are present.
 
D. PERMETHRIN*
  (Pounce 3.2 EC) 4-8 oz 12 see comments
  MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.
  COMMENTS: Do not use more than 0.2 lb a.i./cutting. Do not apply to mixed stands with intentionally grown forage grasses and/or legumes. Preharvest interval is 0 days for 4 oz/acre and 14 days for more than 4oz/acre.
 
 
**  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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