MSU Extension: Growers must scout now as onion thrips move into celery fields

Michigan State University Extension is advising celery growers to begin scouting fields now as onion thrips are moving out of maturing onion fields and into nearby celery, where populations can build quickly under hot, dry summer conditions.

According to an MSU Extension grower alert, onion thrips often migrate into celery after onion foliage begins to dry down. Once established, the insects feed by rasping leaf tissue and sucking out plant contents, which can reduce plant vigor and market quality if infestations are left unchecked.

Extension specialists recommend that growers scout fields frequently, paying particular attention to field edges adjacent to onion plantings where migrating thrips are often detected first. Early detection can help prevent populations from reaching damaging levels.

MSU Extension also stresses the importance of rotating insecticides with different modes of action to reduce the risk of insecticide resistance. Repeated use of products from the same IRAC group can reduce long-term effectiveness, making a diversified spray program an important component of integrated pest management. The guidance encourages growers to follow label directions carefully and base treatment decisions on field scouting results rather than calendar-based applications.

Weather conditions also play a role in thrips activity. Warm, dry conditions favor rapid population growth, making regular field monitoring especially important during periods of summer heat.