Fall Pests in the Willamette Valley

Bob Schroeder
CPS Tangent


A number of common pests are reeking havoc in Willamette Valley fields this fall.  Pressures are heavier in some areas and crops than in others but even small populations are wide spread this fall.  

Cutworms - Agrostis species
The eggs are a pearly white, rounded and about 0.5 mm in diameter.  You will find them in clusters or singly, laid on vegetation, moist ground around plants, and in cracks in the soil.  One CPS fieldman even found clusters of them on his field flag.   The larvae (caterpillars) can be plump, smooth caterpillars that are greasy in appearance and can range in color from grey to brown or black.  The larvae curl into a C shape when they are disturbed and remain motionless for a short time.  They can blend in well with the soil, making them difficult to distinguish.  They commonly hide just below the soil surface or in residue during the day.  
Cutworms generally feed at night or during overcast and foggy days of which we have had many in October.  Young larvae feed on plants leaving small irregular holes in the leaves.  Larger larvae may completely cut through the stocks of plants.  When populations are heavy, they can destroy as much as 75% of a crop and are particularly tough on new seedings.  Most damage occurs between June and November.  There are several control options.  Consult with your fieldman for the most effective means of control.  For additional information follow the link below.

Cutworms in the Pacific Northwest


Grass Seed Wireworms
Wireworm larvae are the damaging stage of this pest that are yellow-brown and up to 0.5 inches long.  Larvae feed on the roots and into the crowns of plants, killing or severely stunting their growth.  The damaged seedling stands often appear yellow, and the plants eventually turn brown and die.  The larvae migrate up and down in the soil profile as moisture changes.  

Grass Seed Wireworm