ISSUE #378 A

Attention to Weed and Insect Control Gold Standards

Minimize Crop Loss Risks

3-31-2000

Figure 1 summarizes the anticipated sugarbeet root maggot population levels for the Red River Valley during the 2000 growing season. In the area of Wahpeton and north to Reynolds in North Dakota, and from Foxhome and Breckenridge north to Climax in Minnesota’s beet-producing counties can expect low to moderate maggot populations. However, producers in the zone from Reynolds, ND and Crookston, MN north to the Grand Forks/East Grand Forks area will likely experience moderate pressure. It should also be noted that survey information suggests that a small area between Casselton and Amenia could experience moderate sugarbeet root maggot pressure this year. Shareholders between Grand Forks and Grafton and along a narrow line on the eastern edge of Walsh and Pembina counties in North Dakota and adjacent areas in northwestern Minnesota can expect moderate to high populations during the 2000 season. Very high levels of sugarbeet root maggot pressure are anticipated from Grafton north to the Canadian border. Yield loss of 3 - 5 tons per acre occurred in some fields in this area in 1999. It is important to recognize that these forecasts are general in nature, and will not always be precise on an individual field basis.

Figure 1

378

Shareholders in the northern 1/3 of the Red River Valley should be especially attentive to the relative levels of fly activity in their fields during late May and through the month of June. It is likely that many of those producers will need to apply a postemergence insecticide for adequate protection of their beet crop from the maggot during the 2000 growing season.

Sufficient control of the sugarbeet root maggot will often be achieved by using planting-time granular soil insecticides, especially in areas that typically have low maggot population levels. The radio, DTN, the Internet, and selected weekly issues of the NDSU Crop & Pest Reportwill be used for updates on fly activity and population levels during late May and throughout the month of June. However, growers should also monitor individual fields for significant fly activity. Agriculturists will have up-to-date information on a daily basis regarding incidence and severity of root maggot infestations.

In cases where a postemergence insecticide is needed, a consideration of soil moisture can help determine the best treatment choice. If soil moisture conditions are adequate, postemergence granules will be the better choice. However, a postemergence liquid will yield better results than a granular material under dry conditions. Timing of post treatments will be critical to their performance. To be successful, the application should be made prior to peak fly activity. Although rainfall events are difficult to predict very much in advance, a good rain following the post treatment will enhance control. Ideally, if rainfall is likely within 7-10 days prior to peak fly activity, the insecticide application should be made before the rain.

Kochia Management For Sugarbeet Rotations

The incidence of ALS herbicide-resistant kochia has increased dramatically in recent years. The problem may be slightly more severe in the northern Red River Valley, but resistant kochia is present in every factory district.

  • ALS resistance is spread by kochia pollen.
  • Tumbling of mature plants spreads seeds.
  • Tillage and harvest equipment spread seeds and plants.
  • Kochia plants produce an average of 14,600 seeds/plant.

Growers must:

  • Assume all kochia is ALS resistant or will become resistant with repeated exposure to ALS inhibitor herbicides.
  • Use an alternative mode of action
  • herbicide to control ALS-resistant kochia in other crops.

Management practices to consider:

  • Thorough preplant tillage will control early emerging kochia.
  • Use pre-emergence burndown herbicides for control of early emerging kochia.
  • If practical, plant known kochia problem fields last to allow more complete emergence, thus allowing control by tillage or burndown herbicides.
  • Soil-applied Nortron provides excellent kochia control.
  • Correct early identification of weeds is critical.
  • Apply the correct post herbicide solution according to the weeds identified.

Herbicide injury-reduction strategies include:

  • It is strongly suggested to use conventional rates of Progress™ to control .25" dia. Kochia or larger.

    • Spray in late afternoon after temperatures decline.
    • Adjust rates according to environmental conditions.
    • Adjust rates according to sugarbeet stage.
    • Include UpBeet™ for improved control of redroot pigweed.
  • Micro-Rates will not control large ALS-resistant kochia.
  • If using Micro-Rates and kochia is present, then Progress Micro-Rates should be utilized. However, Progress Micro-Rates may not provide adequate control of ALS-resistant kochia.
  • Kochia is a cool-season weed, return to Micro-Rate applications when it stops emerging.
  • Hand labor may be needed to remove escaped kochia plants.

Kochia Control In Other Crops:

Control kochia in other crops with herbicides that are not ALS inhibitors, i.e., Bronate™ or Starane™ in cereals, Liberty or Roundup, and other products in other crops.

Refer to pages 94 and 95 in the 2000 North Dakota Weed Control Guide for a listing of ALS inhibitor herbicides to avoid using on other crops in sugarbeet rotations.

Effective control of kochia the two years prior to planting beets will reduce the live kochia seed survival in soil by 98% or more. Shareholders would then have a greatly reduced kochia population that could be more easily managed.

Thanks to Dr. Mark Boetel, NDSU Sugarbeet Entomologist, for assistance with this issue of the Ag Notes.