Description of the Pest
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.
Damage
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.
Management
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 per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | ZETA-CYPERMETHRIN* | |||
| (Mustang) 1.5EW | 3.4–4.3 oz | 12 | 1 | |
| 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. | ||||
| B. | PERMETHRIN* | 0.1–0.2 lb a.i. | 12 | 1 |
| (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. | ||||
| C. | OXAMYL* | |||
| (Vydate L) | 1–2 qt | 48 | 27 | |
| MODE OF ACTION GROUP NUMBER1: 1A | ||||
| COMMENTS: Do not apply more than 3 gal/acre/season. | ||||
| D. | MALATHION | 1.5 pt | 12 | 7 |
| MODE OF ACTION GROUP NUMBER1: 1B | ||||
| COMMENTS: Apply on fresh market celery only; do not use on celery grown for seed or oil. | ||||
| E. | METHOMYL* | |||
| (Lannate LV) | 1.5–3 pt | 48 | 7 | |
| 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. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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. |
| 1 | Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Rotate pesticides 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 to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. |