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.
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.
Pesticides and Natural Enemy Releases
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. Entries with a similar IPM value are indicated with the same letter ranking. 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. When tank mixing, observe all directions for use on all labels, and employ the most restrictive limits and precautions.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(fish) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Brigade WSB | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
Tank mix only, see comments | 12 | 5 | Bifenthrin alone does not kill small nym... | broad | high | high | high | long | intermediate | low | extra high | very low | intermediate | 02/2020 | ||
|
|
Admire Pro | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
4A |
1.4–3.5 fl oz | 12 | 7 | Highly toxic to bees. Do not apply more... | narrow | — | — | high | short to moderate | — | — | — | — | — | 02/2020 | ||
|
|
Admire Pro | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
4A |
7–14 fl oz | 12 | 7 | Highly toxic to bees. Do not apply more... | narrow | — | — | high | short to moderate | — | — | — | — | — | 02/2020 | ||
|
|
Pounce 25 WP | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
Tank mix only, see comments | 12 | 0 | Do not use as a standalone application.... | broad | low | high | high | long | intermediate | low | extra high | very low | intermediate | 02/2020 | ||
|
|
Actara | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
4A |
3 oz | 12 | 4 | May be tank mixed with bifenthrin at the... | narrow | — 13 | — | moderate | moderate | very low | very low | low | high | high | 02/2020 | ||
|
|
Mustang | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
3A |
4.3 fl oz | 12 | 5 | Do not apply more than 17.2 fl oz of Mus... | broad | high | moderate | moderate | moderate | intermediate | low | extra high | low | high | 02/2020 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. 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.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
- 13 ↩ May cause an increase in spider mite numbers.
UC IPM Pest Management Guidelines: Artichoke
UC ANR Publication 3434
M.A. Bari, Artichoke Research Foundation, Salinas
E.T. Natwick (emeritus), UC Cooperative Extension Imperial County
A. Del Pozo-Valdivia, UC Cooperative Extension Monterey County
Acknowledgement for Contributions to Invertebrates
W.E. Chaney (emeritus), UC Cooperative Extension Monterey County
W.L. Schrader, UC Cooperative Extension San Diego County
L. Handel, Kleen Globe, Inc., Castroville
T.K. Shannon, Kleen Globe, Inc., Castroville
