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UC Pest Management Guidelines


Adult lygus bug, Lygus hesperus.

Artichoke

Lygus Bug

Scientific name: Lygus hesperus

(Reviewed 1/07, updated 6/09)

In this Guideline:


DESCRIPTION OF THE PEST

Lygus bugs can be a pest of summer artichokes and artichokes grown in annual plantings. Adults are about 0.25 inch long, oval, and rather flattened. They are greenish or brownish and have reddish brown markings on their wings. In the center of their back they have a distinct, but small, yellow triangle that helps distinguish them from other insects such as proba bug. The immature forms are pale green and look similar to an aphid. They can easily be distinguished from aphids by their more rapid movements.

DAMAGE

Lygus nymphs and adults feed mainly on the very young leaves that are in the frond stage. As they feed with their piercing-sucking mouthparts, they inject a toxin into the plant that is the primary cause of the injury and results in the death of the leaf tissues around feeding wound. As the developing leaves expand, the feeding punctures turn into brown necrotic spots that fall off, leaving the leaf with a shot-hole appearance. In a severely infested artichoke field, affected leaves are abnormally small and light yellow; as the leaves age they turn brown.

Lygus bug also feeds at the base of the young artichoke bud, causing it to turn partially or completely black and rendering it unmarketable.

MANAGEMENT

Controlling weeds along roadways, ditches, and field borders near artichoke fields to help prevent spring buildup of lygus bugs is fundamental to lygus management in artichokes. Monitor both weeds and crops to detect potential problems with this pest.

Biological Control
Naturally occurring predators that feed on the nymphal stages of lygus bug include bigeyed bugs (Geocoris spp.), damsel bugs (Nabis spp.), minute pirate bugs (Orius tristicolor), and several species of spiders.

Cultural Control
In January, overwintered lygus bugs lay eggs in weeds; eggs hatch in March. Carry out weed control measures in March and early April while lygus are still nymphs. Once adults are present on weeds, they will migrate into artichokes when the weeds are removed. To avoid adult migration in spring, mow or disc under cover crops, especially legumes, before they flower and while lygus are still in the nymphal stages.

It is possible to plant flowering plants such as wild radish or mustard in or adjacent to fields to try to attract and control lygus bug adults before they move into artichokes, but this approach requires careful monitoring and management to prevent an even greater problem. Adult lygus will lay eggs on the flowering plants, and nymphs will emerge from late March through April. The nymphs must be controlled at this time before they become adults and move to the artichoke planting. Destroying the plants by discing or mowing is the most effective method of removing the infested flowering plants.

Cut bare stalks at the base and remove them from the field or disc them under at harvest. This practice, called stumping, will kill the immature stages (eggs and nymphs) that would otherwise reinfest plants. Remove any coyote brush in the immediate vicinity of the field as it may harbor large number of proba bugs.

Organically Acceptable Methods
Biological and cultural controls are acceptable for use on organically certified crops.

Monitoring and Management Decisions
In March, monitor for the first appearance of lygus nymphs on weed hosts to determine when these weeds should be destroyed. Monitor the crop at weekly intervals and treat if there is an average of three or more lygus bugs/shoot.

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

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to impact on natural enemies and honey bees and to the environment.
 
CROP'S VEGETATIVE STAGE
A. METHIDATHION*
  (Supracide) 25W 4 lb 3 days see comments
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Application allowed during the nonproductive phase of the crop only; do not apply after buds begin to form.
 
ALL STAGES OF CROP
A. IMIDACLOPRID
  (Provado) 1.6F 4–10 oz 12 7
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply more than 40 oz/acre/crop season. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area.
 
B. BIFENTHRIN*
  (Brigade) WSB 16 oz 12 5
  (Brigade) 2 EC 6.4 fl oz 12 5
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Do not exceed 0.5 lb a.i./acre/season.
 
C. PERMETHRIN*
  (Pounce) 25WP 6.4–19.2 oz 12 0
  (Pounce) 3.2 EC 4–12 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Mixing bifenthrin and permethrin at their half rate give acceptable control at less cost. When pesticides are used in tank mixes, observe all directions for use on crop, rates, dilution ratios, precautions, and limitations that appear on the labels of all products used in the mixture.
 
+ 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.
1 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 to help prevent the development of resistance. 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 Group numbers are 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: Artichoke
UC ANR Publication 3434
Arthropods
M. A. Bari, Artichoke Research Foundation, Salinas
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Arthropods:
W. E. Chaney, UC Cooperative Extension, Monterey County
W. L. Schrader, UC Cooperative Extension, San Diego County
L. Handel and T. K. Shannon, Kleen Globe, Inc., Castroville, CA

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