The Pacific Northwest Pest Alert Network reported a sharp increase in thrips numbers in most areas monitored over the past week.
Fields were checked on Thursday and Friday (5/30 – 5/31). Thrips were in 90% of the fields checked and are being found on more plants per field now.
The overall increase was largely a result of thrips beginning to reproduce in fields (as marked by the increase in immature thrips). Numbers tend to be higher in fields with larger plants.
The highest numbers have been in red onion fields with plants at the 4-5 leaf stage and in early onion fields (e.g. Spanish Medallion and other early varieties). The highest numbers in the network were about 32 per plant in a red onion field (about 85% being immatures). The lowest numbers have been in fields at the 1-2 leaf stage, especially those in the Oregon Slope/Weiser area.
The Network warns to expect additional movement of thrips into onion fields as more alfalfa fields get their first cutting and as rangeland weeds begin to dry down and senesce.
Populations will increase rapidly with the warmer, drier weather in the forecast.
