Agriculture: Artichoke Pest Management Guidelines

Lygus Bug

  • Lygus hesperus
  • 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 per shoot.

    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. THIAMETHOXAM
      (Actara) 3 oz 12 4
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: Highly toxic to bees. Do not exceed a total of 6 oz Actara (0.094 lb a.i.)/acre per growing season. Consider using another insecticide for lygus bug if proba bug infestations are expected; thiamethoxam provides good control of proba bug, but the maximum use amount per season is restrictive.
     
    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 exceed a total of 6 oz Actara (0.094 lb a.i.)/acre per growing season. Consider using another insecticide for lygus bug if proba bug infestations are expected; thiamethoxam provides good control of proba bug, but the maximum use amount per season is restrictive.
      ...OR...
      PERMETHRIN
      (Pounce 25 WP) 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) Foliar: 1.4–3.5 fl oz
    Soil: 7–14 fl oz
    12 7
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: Highly toxic to bees. Do not apply more than 14 fl oz Admire Pro (0.5 lb a.i.)/acre per crop season.
    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.
    1 Rotate insecticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).
    Text Updated: 01/07
    Treatment Table Updated: 02/20