Armyworm Damaging Silage and Pasture Crops, July 21

News release OSU Extension Agent Cassie Bouska.  I have begun to receive reports of armyworm damage in Coos and Curry County pastures this year.   I would encourage all producers to scout fields for this pest.  Hundreds of acres of grass pastures and field corn can be severely damaged within one week. The armyworm caterpillars feed on plants at night and hide under vegetation near soil level during the day.  Take a flashlight out to fields at night to look for them.  The moths are light brown with a white dot on the wings.  They fly at night and can be seen near bright lights around buildings. Armyworms have multiple generations per year.  It is reasonable to expect at least one more hatch this summer and perhaps a second in the fall.  Because of this, it is recommended that you continue monitoring pastures throughout the season. Harvest early if armyworm larvae reach populations of 5-10/sq. ft.  Cutting the forage in and surrounding an infestation site removes their food source and can help in control.  Entrust® (Dow Agrisciences) was shown to be extremely effective in 2005 pasture trials. Entrust® and Entrust®SC are both organically certified.  Success® is the same product as Entrust®SC, but is labeled for non-organic use.  Neither Entrust nor Success are restricted-use pesticides, so a pesticide applicator license is not required to use them on your property. Always read and follow the label.  Insecticides such as Entrust and Success are most effective when the armyworm larvae are small; there is little benefit to spraying when the pest is full grown. See Armyworms in Grass Pastures and Corn in Western Oregon, an Oregon State University publication, for more detailed information and photos of armyworm adults and larvae (https://catalog.extension.oregonstate.edu/em8919). Please contact me at the office (541-572-5263 ext. 25290) or email (cassie.bouska@oregonstate.edu) if you have any questions or need help.