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A simple way to scout cutworms

Friday, April 15, 2005
filed under: Insects

Seed treatments such as Cruiser (a.i. thiamethoxam) are gaining in popularity, because of their demonstrated success in controlling early-season insects in sunflower, such as wireworms and flea beetles.

Mark Jirak, crop manager for Syngenta Seed Treatment, says that more than 35% of sunflower acres planted in 2004 were treated with Cruiser. The number of treated acreage is expected to be even greater this year, spurred on by grower observations of treatment successes last year, as well as the availability in 2005 of a new insecticide-fungicide combination (Cruiser DM) that will control early season diseases in sunflower as well, including downy mildew.

Keep in mind, however, that the product shouldn’t be expected to control insects (or diseases, in the case of the DM formulation) beyond those listed on the product label.

Cutworms and stem weevils, for example, are not pests listed on the Cruiser label. Some have observed that Cruiser may help protect plants from cutworms early in the season. But the product shouldn’t be expected to offer complete control, especially as the growing season progresses, since it is not labeled for cutworms.

As well, there is consensus among experts that Cruiser won’t be effective in controlling stem weevils, also not on the Cruiser label. Scouting and control measures for stem weevils generally take place between late June and mid July, when residual activity of the seed treatment will have waned.

ATV sprayer scouting method

Three or four days after planting sunflower, Tim DeKrey, a Steele, N.D. grower, mixes the labeled rate of an insecticide for cutworms in his ATV-mounted sprayer with a 10-ft boom. He then makes a diagonal spray pass across a sunflower field – He comes back about an hour before sunset and again around sunrise to check dead cutworms in the treatment path. Scout early after the sample spray, he stresses, to get a good count.

He sprays if there’s an economic threshold - North Dakota State University recommends that treatment is warranted when one cutworm is found per square foot. DeKrey sprays Warrior at 2 fl oz/ac (labeled rate is 1.28 – 2.56). Other labeled insecticides would work as well. “I use Warrior simply because if you find something that works, you tend to stick with it,” he says.

DeKrey says his ATV sprayer scouting method works best in a tilled or minimum till field. “The dead cutworms that come to the surface are easier to see. With my sprayer method, they’re harder to see in no-till residue. I don’t run the ATV through the no-till ‘flowers. With the increased cutworm populations we’ve had the last few years in no-till, I just go ahead and automatically spray it.”

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