Potato, Irish-Lygus bug

Includes tarnished plant bug (Lygus hesperus, L. elysus, L. keltoni)

Pest description and crop damage Adults are less than 0.25 inch long and marked with a "V" shaped or triangular mark on the back. Color ranges from light green to shades of brown or black. Nymphs are 0.04 to 0.25 inch in length, green or yellow-green, with black spots on the back. Adults and nymphs damage plants by inserting their mouth parts into the plant tissue and sucking juices. Lygus are considered "cell feeders". Damage symptoms include flagging of leaflets, leaves, or small stems; damaged leaves wilt and the branch dies. Adults and nymphs prefer to feed on the top third of the plant canopy.

Biology and life history Lygus species, such as the tarnished plant bug, feed on many different plants including weeds, crops, and native species. Alfalfa and quinoa fields often develop very large populations of lygus from which the insects may colonize potato. Lygus can be found throughout the growing season and are common throughout the PNW. There are usually three or four generations each year. For more information, see https://catalog.extension.oregonstate.edu/em9173.

Scouting and thresholds Lygus are easily found during normal scouting operations using a beating sheet/tray technique/inverted leaf blower or observing insect activity while walking through the crop. Both adults and nymphs of all sizes are likely to be present at the same time. There are no established treatment thresholds for lygus in potatoes.

Management-biological control

Generalist predators in potatoes such as Geogoris, big-eyed bugs, and Nabis, damsel bugs, are known to prey on lygus adults and nymphs. There are also braconid wasp parasitoids attacking lygus in the PNW.

Management-chemical control: HOME USE

  • azadirachtin (neem oil)-Some formulations OMRI-listed.
  • carbaryl
  • cyfluthrin
  • deltamethrin
  • esfenvalerate
  • horticultural oil-Some formulations are OMRI-listed for organic use.
  • kaolin-Applied as a spray to foliage it acts to repel certain insect pests. Some formulations are OMRI-listed for organic use.
  • permethrin
  • plant essential oils (garlic, peppermint, rosemary, etc.)-Some formulations are OMRI-listed for organic use.
  • pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin

Note: Pyrethroid insecticide (Group 3 in Tables 1-2) applications make aphid management more difficult and can lead to outbreaks of aphids, thrips, and spider mites.

Management-chemical control: COMMERCIAL USE