UC IPM: UC Management Guidelines for Lygus Bug on Celery

UC Pest Management Guidelines

Celery

Lygus Bug

Scientific Name: Lygus hesperus

(Reviewed 10/05, updated 6/08)

In this Guideline:

Description of the pest
Damage
Management

Adults are small (about 0.25 inch), variably colored yellowish to green to bronze true bugs with a distinctive triangular marking on the back and wings composed of both membranous and hardened sections that are carried folded over the back. The mouthparts are needlelike and long in relation to the body size.

Eggs are laid in plant tissue. Immature lygus bugs are light green and resemble adults in shape but lack wings. The wings gradually appear with each molt. First- and second- instar nymphs are often confused with aphids on casual observation but lack cornicles and move much more quickly.

Lygus feed by piercing cell membranes. This activity affects the subsequent cell division in the area of feeding. The result is sunken, callused, elongated lesions, frequently just below the first node of the celery stalk. Inner petioles may show black spots, twisting, or other distortion, especially if immature lygus are present.

Biological Control
Natural enemies, especially parasitic wasps that attack eggs or nymphs, help control lygus populations. However, in native vegetation where populations of lygus build, natural enemies are not effective at preventing large numbers of adults from migrating into crops such as celery. The most important predators of lygus bugs are bigeyed bugs, which feed on eggs and young nymphs. Lygus adults are more difficult for predators to capture than nymphs because of their quick movements.

Cultural Control
Encouraging natural populations of lygus parasites and managing populations of lygus in nearby weeds may contribute to the suppression of a lygus population.

Organically Acceptable Methods
Biological and cultural controls are acceptable for use on organically grown produce.

Monitoring and Treatment Decisions
Lygus bugs frequently move into crop fields in spring when weeds and native vegetation dry down. Consequently, large numbers of lygus can move into celery fields in a short period of time. Determining the level of lygus infestation is difficult because the insects are cryptic and their activity cycle during any day varies greatly. Lygus become inactive and secretive during temperature extremes and windy conditions.

Because of the severity of the damage to celery, the threshold, while not specifically established, is very low. Sweep nets and keeping a careful eye out for adults flying in front of your movement through the field are the only ways to check for lygus. Sticky traps are not useful for monitoring these pests.

Common name

Amount/Acre

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

When choosing a pesticide, consider information relating to water quality and impact on natural enemies and bees. Not all registered pesticides are listed. Always read label of product being used.

ZETA-CYPERMETHRIN*

(Mustang) 1.5EW

3.4–4.3 oz

MODE OF ACTION GROUP NUMBER¹: 3

COMMENTS: Make applications at least 7 days apart. Do not apply more than 0.3 lb a.i./acre/season.

PERMETHRIN*

0.1–0.2 lb a.i.

(Ambush, Pounce) 25WP

6.4–12.8 oz

MODE OF ACTION GROUP NUMBER¹: 3

COMMENTS: Do not apply more than 2 lb a.i./acre/season. Do not use if leafminers are present.

OXAMYL*

(Vydate L)

1–2 qt

MODE OF ACTION GROUP NUMBER¹: 1A

COMMENTS: Do not apply more than 3 gal/acre/season.

MALATHION

1.5 pt

MODE OF ACTION GROUP NUMBER¹: 1B

COMMENTS: Apply on fresh market celery only; do not use on celery grown for seed or oil.

METHOMYL*

(Lannate LV)

1.5–3 pt

MODE OF ACTION GROUP NUMBER¹: 1A

COMMENTS: This material is very disruptive to parasites and predators. If worms must also be controlled, it can be used to control lygus; otherwise its use is not recommended. Do not apply more than 7.2 lb a.i./acre/crop.

PYRETHRIN/ROTENONE

(Pyrellin E.C.)

1–2 pt

12 hours

MODE OF ACTION GROUP NUMBER¹: 3 and 21

COMMENTS: Provides moderate control.

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 to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.

Permit required from county agricultural commissioner for purchase or use.

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/.

UC IPM Pest Management Guidelines: Celery
UC ANR Publication 3439
Insects
L. D. Godfrey, Entomology, UC Davis
J. T. Trumble, Entomology, UC Riverside
Acknowledgement for contributions to Insects:
W. E. Chaney, UC Cooperative Extension, Monterey County

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How to Manage Pests

UC Pest Management Guidelines

Celery

Lygus Bug

Scientific Name: Lygus hesperus

DESCRIPTION OF THE PEST

DAMAGE

MANAGEMENT

PUBLICATION