Cereal Leaf Beetle

The Cereal Leaf Beetle, Oulema melanopus (L.), is in an outbreak mode this spring all over the Tri-State Region.

Preferred hosts are spring oats, barley, spring, wheat, and some perennial grasses. The adults feed in the spring on developing winter wheat, which is not a host. But scouting for white stripes on winter wheat will cue the field scout’ to the presence of adult females. In the fall adults feed but do not reproduce on corn leaves. The adult females over winter in shelters (CRP, riparian grass zones, etc.) Eggs are laid on developing host plants in the late spring.

Damage is made by larval feeding on preferred hosts.Many people are requesting what chemical to use and when to spray for larvae. Actually as of now, we do not have researched based information on economic thresholds by crop in the PNW. People are spraying when they see larvae, and are not basing sprays on economic thresholds!

My old friend and CLB Pioneer, Jay Karren, USU, Logan (ret,) has a handle on spring oats in Utah with almost total leaf surface loss occurring. The old wheat rule was that 2/3 of the flag leaf plus lower leaves could be removed and yield would not be affected. In my own trials, I have leaf surface loss to ca. 67% ranging from 5 to 30% as a mean. I am trying to measure economic thresholds this spring.

CLB is highly parasitized by hymenopterous parasitoids, and several predators including ladybird beetles feed on the eggs and larvae reducing field populations. Spraying will affect the natural enemies more than the beetles. So field insectaries for the parasitoids are being established in protected locations around the PNW with great success to date.

CLB is a political pest under quarantine from other states such as California. The problem is not crop injury on our end. But, adult beetles stow away in potted plants such as Mugo Pines grown in the Willamette Valley of Oregon.