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How to identify it
- Adults are about 3/16 to 1/4 inch long, with a metallic bluish-black head and wing covers, an orange to reddish thorax and long, beaded antennae.[1][3][2]
- The larvae are yellowish under a shiny, slimy coat of mucus and their own feces, which makes them look like tiny slugs on the leaf.[1][2][3]
- The eggs are yellow to orange, about 1/16 inch long, and laid singly or in pairs along the midrib on the upper side of the leaf; they darken before hatching.[1][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Collops beetles | These beneficial predators are similar in size and color but have shorter wing covers that leave the red tip of the abdomen exposed, and their legs are not red.[2] |
Where it lives
Native to Europe and Asia, it was first found in the United States in a Michigan grain field in 1962 and has spread through most small-grain areas of the country, reaching Utah by 1984 and well established in Montana and North Dakota.[4][1][2]
Biology and life cycle
Adults spend the winter in leaf litter in woodlots, hedgerows and similar shelter, then fly to grain fields from mid-March into April, feeding for two to three weeks before laying eggs.[1][3]
They prefer young plants, so spring-planted oats and late-planted wheat take most of the eggs.[3]
Larvae feed for about 10 days to three weeks, then drop and burrow an inch or two into the soil to pupate; new adults appear about two weeks later.[3][2][1]
The new adults feed briefly in grain and corn fields, rest for most of the summer, and fly back to wooded shelter in the fall. There is one generation a year.[1][4]
Damage and signs
- Older larvae do most of the damage, scraping the green tissue from the upper leaf surface in long, narrow strips between the veins without chewing through the leaf.[1][2]
- Heavy infestations give fields a white, frosted look and can reduce yield and grain quality; adult feeding has not been shown to matter economically.[1][2]
- Utah State notes that its presence in grain can restrict shipments to counties and states that don't have the beetle.[4]
Health risk
It feeds only on grasses and small grains; Penn State, Montana State and Utah State mention no risk to people.[1][2][4]
Control
Prevention
Damage is worst in thin or poorly established stands, so good crop management controls it in many fields; in Delaware, planting wheat right after the Hessian fly-free date has also helped.[1][3]
Biological control
Introduced parasitic wasps, especially Tetrastichus julis, kill many larvae where they are established, and predatory beetles help hold populations down.[2][1][4]
Pesticides
Scout each field early in spring for eggs and young larvae, since populations are spotty. Penn State suggests treatment is probably warranted at one or more larvae per stem, especially before the flag leaf; target the larvae, because spraying adults hasn't proved effective.[1][3][2]
Common questions
- Why do cereal leaf beetle larvae look slimy?
- They coat themselves in mucus and their own fecal pellets, which protects them from predators and from drying out.[1][2]
- Should I spray when I see the adult beetles?
- No. Penn State says adult feeding isn't economically significant and targeting adults hasn't worked; the larvae are the stage to scout for and manage.[1]
Sources
- Penn State Extension, “Cereal Leaf Beetle (updated May 12, 2026).” extension.psu.edu/cereal-leaf-beetle (accessed 2026-10-19)
- Montana State University Extension, “Pest Fact Sheets: Cereal Leaf Beetle (MontGuide MT201604AG).” extension-store.montana.edu/montguides/pest-fact-sheets-cereal-leaf-beetle (accessed 2026-10-19)
- University of Delaware Cooperative Extension, “Cereal Leaf Beetle Control in Small Grains (J. Whalen, reviewed by D. Owens, April 2025).” www.udel.edu/content/dam/udelImages/canr/pdfs/extension/factsheets/Cereal-Leaf-Beetle-Control-in-Small-Grains.pdf (accessed 2026-10-19)
- Utah State University Extension and Utah Plant Pest Diagnostic Laboratory, “Cereal leaf beetle, ENT-84-07PR (August 2007).” extension.usu.edu/planthealth/uppdl/files/factsheet/cereal-leaf-beetles07.pdf (accessed 2026-10-19)
- iNaturalist, “Oulema melanopus taxon page (order and family).” www.inaturalist.org/taxa/1370475 (accessed 2026-10-06)