How to Manage Pests

UC Pest Management Guidelines

Artichoke

Lygus Bug

Scientific name: Lygus hesperus

(Reviewed 1/07, updated 6/09, pesticides updated 5/15)

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 per acre R.E.I.‡ P.H.I.‡
(Example trade name)   (hours) (days)

UPDATED: 5/15
  Calculate impact of pesticide on air quality
 
The following are ranked with the pesticides having the greatest IPM value listed first—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. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. THIAMETHOXAM
  (Actara) 3 oz 12 4
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Highly toxic to bees. Do not directly treat or allow it to drift onto blooming crops or weeds if bees are foraging. Do not exceed a total of 6 oz Actara (0.094 lb a.i.)/acre per growing season. If proba bug is a problematic pest, consider using another insecticide since thiamethoxam provides good control of proba and the maximum use amount is low.
 
B. BIFENTHRIN*
  (Brigade WSB) 16 oz 12 5
  (Brigade 2 EC) 6.4 fl oz 12 5
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Bifenthrin alone does not kill small nymphs. Tank mixing provides control in strawberry, but these chemicals together have not been studied in artichoke. Do not exceed 0.5 lb a.i./acre per season.
  ...PLUS...
  THIAMETHOXAM
  (Actara) 3 oz 12 4
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Highly toxic to bees. Do not directly treat or allow it to drift onto blooming crops or weeds if bees are foraging. Do not exceed a total of 6 oz Actara (0.094 lb a.i.)/acre per growing season. If proba bug is a problematic pest, consider using another insecticide since thiamethoxam provides good control of proba and the maximum use amount is low.
  ...or...
  PERMETHRIN*
  (Pounce 25WP) 6.4–19.2 oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Mixing bifenthrin and permethrin at half their rate gives 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.
 
C. ZETA-CYPERMETHRIN
  (Mustang) 4.3 fl oz 12 5
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Do not apply more than 17.2 fl oz of Mustang (0.2 lb a.i.)/acre per crop season. Do not make applications less than 14 days apart. See label for buffer zone restrictions.
 
D. IMIDACLOPRID
  (Admire Pro) 3.5 fl oz 12 7
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply more than 14 fl oz Admire Pro (0.5 lb a.i.)/ acre per crop season. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area.
 
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.
1 Rotate chemicals with a different mode of action Group number, and do not use the 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/.
* Permit required from county agricultural commissioner for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Artichoke
UC ANR Publication 3434

Insects and Mites

M. A. Bari, Artichoke Research Foundation, Salinas
E. T. Natwick, UC Cooperative Extension, Imperial County

Acknowledgment for contributions to Insects and Mites:
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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