Cereal Leaf Beetle Concerns

Both Michigan and Ohio are reporting unusually high cereal leaf beetle (CLB) activity in some of their winter wheat fields. Though it has been mainly adults that have been spotted so far, these adults will be laying eggs, giving rise to larvae that do most of the serious injury. Here in Ontario, the typical hot spot regions like Norfolk County are starting to see some adult activity but other regions should be on the alert as well.

Figure 1. Cereal Leaf Beetle Adult
(Jocelyn Smith, U of G, Ridgetown Campus)

What do cereal leaf beetles look like? The adult beetle is actually quite pretty. It is metallic, blue-green in colour with a reddish-orange head and legs (Figure 1). The larvae however are not so pretty. They have a slug like appearance because of they coat themselves with their own fecal matter to stay moist (Figure 2). No, I'm not kidding. If you were to brush off this coating, you would find a small (6 mm) yellow-tan larva (Figure 3). In fact, the best way to know if you have a CLB problem is to wear khaki pants into a wheat field that you are scouting. When you walk out of the field, you will have black marks across your pant legs from rubbing up against their coating. NICE! I've lost a few pairs of pants that way.

Figure 2. Cereal Leaf Beetle Larva with Fecal Coating
(T. Baute, OMAFRA)

Figure 3. What the Larva Looks Like Under the Feces
(R. Coutin, OPIE)

Both adults and larvae feed on the crop, chewing long strips of tissue between the leaf veins, leaving the top layer of the leaf intact (see Figure 2). This creates a window-paning or "skeletonizing" effect. Heavily damaged fields appear silver. Spring cereals tend to be more attractive, particularly late plantings, though winter wheat can also be infested, especially in a year when we are struggling to get any crops in.

Stay ahead of the damage by scouting fields every 5 days as the damage can advance quickly. Examine 20 plants in five locations across the field. It is important to scout various areas of the field, as CLB tends to be unevenly distributed across the field. One CLB adult or larvae per stem, especially in the earlier stages of the crop (before heading) is the threshold. For a list of recommended products, refer to the OMAFRA publication 812, Field Crop Protection Guide at: http://www.omafra.gov.on.ca/english/crops/pub812/5clb.htm