Anasa tristis is one of the squash bugs common in the PNW.
This pest is notoriously hard to detect, because they can hide on the underside of foliage, on plant stems, near irrigation lines, or even under fabric mulch.
Squash bugs use their piercing-sucking mouthparts to feed on leaf tissue and inject their saliva, which causes wilting of leaf tissue and, depending on the species, vectors cucurbit diseases.
Damage tends to be localized but can occur quickly because nymphs are gregarious, and feed alongside adults. If left undetected, vines eventually wilt and die.
Squash bugs have been a problem this year in the southeastern U.S., as noted by this news article.
** 2019 Degree-Day Model Update**:
Adults noted East of the Cascades: June 27th (see report)
Eggs (predicted with GDD model, Corvallis): June 1st
Nymphs (predicted with GDD model for Corvallis): July 17th
Adult 2nd gen. (predicted with GDD model for Corvallis): Aug 4th
FOR MORE INFORMATION
1 H. B. Doughty, J. M. Wilson, P. B. Schultz, T. P. Kuhar, Squash Bug (Hemiptera: Coreidae): Biology and Management in Cucurbitaceous Crops, Journal of Integrated Pest Management, Volume 7, Issue 1, January 2016, 1, https://doi.org/10.1093/jipm/pmv024
2 PNW Insect Management Handbook section
3 This page shows how to differentiate squash bug, BMSB, and others