NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
May 11, 2000
Researchers and scientists from North Dakota State University and the North Dakota Department of Agriculture (NDDA) are preparing for the possible arrival of an unwelcome guest: the cereal leaf beetle, a defoliating insect native to Europe. Because of the history of the cereal leaf beetle's movements in areas of the Corn Belt, the East Coast and some western states, certain shipping restrictions apply to states where the insect becomes established.
"No cereal leaf beetles were detected in our survey last year--or in previous years--but all counties will be surveyed again this year, and the scouts will be looking for this insect, as well as other pest problems," says Marcia McMullen, extension plant pathologist at NDSU. McMullen also coordinates the NDSU Extension Service's Integrated Pest Management (IPM) program and manages an annual statewide survey that monitors disease and insect problems.
Last year, IPM crop scouts surveyed about 725 wheat fields and 150 barley fields. If cereal leaf beetles are detected in this year's survey, the NDDA will be notified, as well as producers in the areas where the insect is located, McMullen says.
Shipments of grain from states where the cereal leaf beetle has been detected are regulated by California law, says Dave Nelson, NDDA entomologist in Bismarck. If the cereal leaf beetle is detected in North Dakota, shipments of barley, oats and wheat destined for California would be subject to those regulations. Nelson offers the following details:
"If cereal leaf beetle is detected in North Dakota, the NDDA would develop programs to allow shippers these various options," Nelson concludes.
Even if the cereal leaf beetle is present in North Dakota, it may take a year or two for its population to build and create any significant production problems, says Gary Brewer, chair of NDSU's entomology department.
The cereal leaf beetle was first identified in the 1960s in Michigan and Indiana. From there, the insect spread to the East Coast to states such as Virginia and North Carolina, Brewer says. In the mid-1980s, the insect became established in Montana and Utah. From there, the cereal leaf beetle moved into Wyoming, Nevada and Idaho. The cereal leaf beetle has now been detected in Montana counties neighboring North Dakota.
"The cereal leaf beetle has a history of slowly moving out from where it originally becomes established," Brewer continues. "When the insect first became established in Michigan and Indiana, it did a lot of damage because, being a non-native, there were no effective biological controls to keep it in check. Fortunately, it does respond well to insecticide treatment. It is easy to control that way with fairly low dosages."
Since the cereal leaf beetle's arrival in the United States, government researchers have established four parasites from Europe that are effective biological controls for the insect in the Corn Belt and on the East Coast, Brewer says. In these regions, cereal leaf beetle is now only an occasional pest.
Brewer says initial research efforts in North Dakota regarding the cereal leaf beetle will determine if the insect is present, and if so, where and at what population levels. Researchers will also need to determine whether any parasites are present in the state. If so, producers can use some cultural practices, such as delaying fall tillage, to enhance the parasites' survival rate.
If none of the parasites is present in North Dakota, researchers will need to decide if some should be introduced. Also, Brewer says researchers will need to study whether pest-control techniques and recommendations developed for other parts of United States will be effective in North Dakota, or if they will need to develop new strategies.
Meanwhile, one bright spot for producers is this: If the cereal leal beetle does establish itself in North Dakota, controlling it will be considerably easier than controlling other insects--specifically the orange wheat blossom midge. Brewer explains, "Both the cereal leaf beetle adult and the larvae defoliate the leaves of cereal plants, but it's the larvae that cause most of the damage, and they don't move around. They'll be on the plant, and they're easy to identify because there probably won't be anything else on the plant that looks like them."
Cereal leaf beetle adults are 3/16 inch long, explains Phillip Glogoza, extension entomologist at NDSU. The adult beetles are brightly colored, which aids in identification and detection. The first pair of wings (the elytra) are hard and are metallic blue-black. The legs of adults and the prothorax (first segment behind the head) are red. The brown-to-black larvae are often covered with black, shiny mucus. Fully grown larvae are 1/4 inch long.
The larvae feed on leaves by eating streaks of tissue from the upper surface of the leaf, Glogoza says. Larvae-damaged leaves have long, narrow feeding strips between the veins. When adults are feeding in the early season, they chew holes completely through the leaf.
"The cereal leaf beetle will feed on leaves of wheat, oats, barley, rye and corn plants, but the preferred host is oats," Glogoza says.
There is only one generation of cereal leaf beetle per year. Adults are first found in the fields as early as April or May. The growth stage when wheat is most vulnerable to feeding damage is from stem elongation to late boot, but the cereal leaf beetle can damage wheat up until the heading stage. In western states where leaf beetles are established, wheat plants averaging one larva per flag leaf have resulted in a yield loss of 5 to 6 bushels per acre.
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Sources: Marcia McMullen (701) 231-7627
Gary Brewer (701) 231-7581
Phillip Glogoza (701) 231-7581
Editor: Dean Hulse (701) 231-6136