Unusual cereal leaf beetle numbers

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Some wheat fields in both northern Ohio and south central Michigan have unusual numbers of cereal leaf beetle adults this spring. From an entomologist perspective, this is exciting, since cereal leaf beetle problems are fairly rare, and it is interesting to see them. Adults beetles are very distinctive metallic, dark blue-black insects with a red thorax. Females lay one to several yellow-orange eggs on the top surface of wheat leaves. The larvae are yellowish, slug-like, and have a fantastic anti-predation strategy. They cover themselves with a moist mixture of mucus and excrement. Larvae scrape or eat leaf strips.

In most years, cereal leaf beetle populations are very low because of biological control. From a management perspective, at this time it is more of a curiosity, but populations bear watching. The most efficient way to scout now is to sweep wheat fields – an interesting population would be one or more adults per sweep. I would appreciate knowing about fields with large numbers of adults or larvae. Please email me at: difonzo@msu.edu.

Below are a few web links to cereal leaf beetle information and pictures. Note that these publications are almost 10 years old. While the biology and ecology information probably hasn’t changed, do not use the insecticide recommendations. If larval populations do eventually increase in some fields, the MSU Insect Guide E1582 does have current integrated pest management recommendations, insecticide products or rates. There are two different thresholds for larvae. Three eggs or larvae per plant at boot stage and one or more larvae per flag leaf after boot stage or 25 eggs or larvae total per 100 tillers.

Photos of cereal leaf beetle:

Note that cereal leaf beetle should have a special place in the hearts of all you native Michiganders, since Michigan was the original introduction point of this non-native pest. Cereal leaf beetle was first discovered in 1962 in Berrien County. A large and eventually very successful biological control program was focused in the state at a USDA-APHIS insect facility in Niles and at Michigan State University in the 1960s and 70s.

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