Time to Scout for Cereal Leaf Beetle

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Begin scouting small grains for Cereal Leaf Beetles (CLB). Over the past few years, we have seen an increase in damage on small grains from cereal leaf beetle larvae. This past week’s Guess the Pest was a picture of adult cereal leaf beetle feeding injury. Adults feed on small grains (wheat, barley, and oats) causing longitudinal slits in the leaves. This damage is not a concern with the exception that it indicates you have adult CLB in your field, mating and laying eggs.

Cereal leaf beetle adult

Damage from CLB adult feeding

Larvae feed on small grain by removing the upper layer of leaf surface. Heavy infestations can result in significant yield losses by hindering the plants ability to photosynthesize. The damage can give a field a “frosted” appearance under heavy infestations. Once plants have reached the hard dough stage, CLB feeding injury will have no impact on yield.

Damage caused by cereal leaf beetle larvae.

Cereal leaf beetle eggs are about a 1/16th of an inch in length, orange and laid singly or in pairs along the leaf mid-vein. Larvae have a brown head and legs with a yellow body often covered with brown or black mucus and feces giving them a black, shiny appearance.

Cereal leaf beetle egg.

Cereal leaf beetle larva.

To scout for CLB larvae, examine 5-10 tillers in 5-10 locations throughout the field. Count the number of eggs and larvae per stem and estimate percent defoliation. The treatment threshold is 25 eggs and/or larvae per 100 tillers. Treatment is suggested when the threshold is reached and approximately half the eggs have hatched.

Research from Virginia and North Carolina determined that a growing degreed day (GDD) model is an accurate way to predict peak egg laying and larval hatch for CLB. Based on the model, we should be at peak egg laying throughout the state. However, keep in mind this model has not been validated for Delaware.

Here is a link to research published using the GDD model to predict peak egg laying and larval hatch:

https://projects.ncsu.edu/cals/entomology/sites/default/files/2012%20Philips%20et%20al.-%20DD%20CLB.pdf

See our Cereal Leaf Beetle Control in Small Grains Fact Sheet for more detailed information on CLB identification, biology, damage, management options, and threshold:

http://extension.udel.edu/factsheets/cereal-leaf-beetle-control-in-small-grains/

For chemical control options, follow the link to our Insect Control in Small Grains Recommendations Guide:

https://cdn.extension.udel.edu/wp-content/uploads/2012/05/18063827/Insect-Control-in-Small-Grains-final-2017.pdf

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