Lygus Bugs (Tarnished Plant Bugs)

Tarnished Plant BugTarnished Plant Bug

Tarnished Plant BugTarnished Plant Bug

Tarnished Plant BugTarnished Plant Bug


  • Beans
  • Peas
  • Potato
  • Tomato
  • Leafy Greens
  • Hemp


Both the tarnished plant bug (Lygus lineolaris) and western tarnished plant bug are (lygus hesperus) are present in Utah. Adults are brown with yellow, black, and red markings and have a yellow or green triangle on the upper center of the back. Nymphs are usually lighter in color with dark spotting and a more rounded form.


Egg | Nymph | Adult
  • 3-4 generations per year.
  • Overwinter as adults in plant debris.


Adults and nymphs feed on plant cells (not sap) with piercing-sucking mouthparts. Feeding on seeds causes them to shrivel and heavy feeding on flowers may cause bud drop or flower abortion. Symptoms on foliage have not been documented.


  • Remove preferred hosts (flowering
    weeds, legumes, alfalfa) from field
  • Control weeds within the field. 
Time for Concern: Summer to harvest.

When and Where to Scout: Visually scout plants or use a sweep net in nearby weeds and regularly examine flowers to monitor for adults and nymphs. Monitor weeds surrounding the crop for plant bug activity. 

Threat Level: Low to Medium. Hemp grown for CBD oil is not likely to be damaged but plants grown for seed may need closer monitoring.

Occurrence in Utah: Lygus bugs are present in low to average numbers in all hemp fields, but no economic damage has been documented.


Treatment decisions should be based on sweep net counts. Applications should be delayed until egg hatch is complete but before the nymphs reach the 4th-5th instar. Broad spectrum insecticides will reduce or eliminate pollinators and beneficial insects such as predatory bugs, parasitic wasps and spiders.

Several products are registered for lygus bug control in Utah alfalfa: beta-cyfluthrin, carbaryl, dimethoate, gamma-cyhalothrin, lambda-cyhalothrin, malathion, methidathion, tralomethrin, zeta-cypermethrin.