Abstract
Thrips insects are currently damaging Idaho alfalfa crops through their feeding. University of Idaho Extension Educators evaluated thrips population growth and associated damage to alfalfa crops during the 2019 growing season. Initially, small populations of both onion thrips and western flower thrips were found in alfalfa fields. Later in the season, large populations of western flower thrips were found in alfalfa. These later populations were associated with damage to the alfalfa crop. Adjacent small grains crops and rabbitbrush stands do not seem to be a source of thrips population build up prior to their movement into alfalfa fields.