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ISSUE 7    June 16, 2005


High numbers of sugarbeet root maggot flies have emerged from the soil during the past few days. Sticky-stakes checked on Monday, June 13 indicated a significant increase in fly activity in the Cavalier, St. Thomas, and Minto areas of the Valley last weekend (Fig 1.). Recent field collections of larvae and pupae suggest that high numbers of flies are yet to emerge. Therefore, the flies that have entered beets to date may be just the tip of the iceberg. A significant increase in fly activity is expected to begin Friday afternoon, and will likely continue through most of next week, pending good flying weather.

The NDSU root maggot developmental model indicates that all monitoring sites in the Red River Valley will have surpassed the necessary 600 degree-day units for peak activity to occur, but recent cool and rainy weather has thus far kept most flies in grain fields, field margins, and shelterbelts. The expected warm and dry weather will lead to a rapid upsurge to peak fly activity in current-year beet during the next few days.

root maggot fly activity map
Figure 1.  Cummulative counts of sugarbeet
root maggot flies captured on sticky stakes
since June 1 (4-stake total per field).

Growers in high-risk areas for maggot attack (central and southern Pembina County, ND and central Walsh County, ND) should apply a postemergence insecticide for added protection. Other areas to watch include the rest of Pembina and Walsh counties, northern Grand Forks county, and the Casselton/Amenia area of Cass cty.

CONTROL OPTIONS: Postemergence granules should work well this year because most soils are moist, and the moisture helps activate the insecticide quickly. Some growers’ fields may be too wet to enter for applying granular insecticides. The need for prompt action to protect fields will necessitate aerial application for those growers this year. Liquid insecticides should be effective if applied 2-3 days before or after peak fly activity. A broad peak in fly activity is expected this year, so applying 2 split treatments of a liquid insecticide may be more effective. If such a program is selected, apply the first treatment as soon as possible, and make the second application within 5 to 7 days.

For more information regarding postemergence root maggot control and for more specific product recommendations, refer to the "Insect Control" section of the 2005 Sugarbeet Production Guide or the "Sugarbeet Insects" section of the 2005 Field Crop Insect Mgmt. Recommendations. These publications are online at:




Always read, understand, and follow all pesticide labeling instructions and precautions - it’s the law.

Mark Boetel
Research & Extension Entomologist

Justin O. Knott
Plant Protection Specialist
ND Dept. of Agriculture



Governor John Hoeven has declared June 2005 "Noxious Weed Awareness Month". All North Dakotan need to do their part to identify and control noxious weeds. The North Dakota state list of noxious weeds includes: absinth wormwood, Canada thistle, field bindweed, leafy spurge, musk thistle, purple loosestrife, Russian knapweed, spotted and diffuse knapweed, yellow starthistle, dalmation toadflax, and saltcedar. These noxious weed species are recognized to harm North Dakota’s agriculture, natural resources and recreational lands, and can have significant detrimental short and long-term effects on these lands. When a weed species is first noticed, often times it clearly is not causing noticeable damage and consequently the land owner/manger waits to take action after the weed patch has grown considerably in size and is a significant problem. As a result, control efforts after weeds are causing significant damage can be too late to be cost-effective or even successful. Invest now in weed identification and control to prevent noxious weeds from establishing on your lands and causing significant economic losses. The following NDSU Extension publications on identification and control of noxious weeds are available at http://www.ext.nodak.edu/extpubs/weeds.htm  or your county Extension Office.

All North Dakotans must do their part to stop the spread and introduction of noxious and new invasive weed species in North Dakota.

Denise Olson
Research Entomologist

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