Army Cutworm Infestation
Ranchers in Owyhee County from south of Homedale (Jump Creek area) down to the Rome area in Malheur County are reporting widespread damage to alfalfa and rangeland grasses by an infestation of army cutworms (Euxoa auxiliaris). These cutworms are ½” to 1 ¼ “ long, are brown to black in color with light colored stripes (picture attached) and may be seen in protected areas such as under cowpies, alfalfa crowns or just underneath the residue layer remaining from last season’s foliage. If you suspect army cutworms, lightly pull back the residue layer about 1” deep and look under cowpies where available. They appear to come off the rangeland fringe into alfalfa fields creating a banded effect similar to what ground squirrels may do this time of year. Crested wheat seedings in BLM allotments have also been damaged (pictured). Ranchers wishing to implement control measures on their irrigated fields can use chlorpyrifos (Lorsban 4E) or a mixture of chlorpyrifos and pyrethroid such as Cobalt at labeled rates. Cutworms are reported to come up at night in some areas so it important to use an insecticide that will be effective by ingestion to be available when the cutworm comes up to feed. For more information, check out the PNW Guide (linked). Big hat tip to Sergio Arispe and Stuart Reitz for their help with this posting!
Click on the link(s) below for more information about this pest:
Onion thrips have been found this week on volunteer onions growing in last year’s onion fields in Malheur, Canyon and Payette Counties. Adult thrips have also been found on sticky traps placed around those fields. Volunteer onions can host onion thrips and Iris Yellow Spot Virus, and act as a reservoir to infest newly emerged onion fields that are nearby. Control of volunteer onions, especially in fields that were heavily infected, before emergence of nearby seeded onion fields may help to reduce thrips and Iris yellow spot pressure this season.