ISSUE #401

401 - Achieving Optimium Sugarbeet Root Maggot Control

6-1-01

Inadequate sugarbeet root maggot (SBRM) control may result in large yield reductions for sugarbeet producers. A complete understanding of the SBRM life cycle will improve the ability of shareholders to maximize control of this insect. The SBRM life cycle is shown in figure 1.

401

Key Life Cycle Facts to Remember:

  • The insect overwinters as a larvae at 6-12 inches deep in the soil.
  • As soil warms in the spring larvae become active and move near the soil surface.
  • Larvae undergo pupation in May and early June.
  • The pupae transform to the adult fly stage in last years beet fields.
  • Flies dry off, wings harden and then they fly to 2001 beet fields.
  • After mating, female flies deposit eggs 1/8 inch below the soil surface next to beet plants.
  • Eggs incubate for 3-7 days and then hatch.
  • Young maggots hatch and immediately begin feeding on the beet root.
  • Feeding intensifies through June and into July and declines in August.

Risk of Yield Loss is higher if:

  • Sugarbeets are planted late
  • Soil and weather conditions are dry – NOT 2001
  • Egg laying occurs when beets are in the cotyledon to 2 leaf stage

Shareholders Can Maximize Insect Control:

  • Use a planting time insecticide
  • Apply a second application of granules in high SBRM population areas
  • Apply postemergence liquid insecticide just before peak fly emergence
  • Rotary hoe fields after egg laying and before they hatch and feed.

Second Granular Applications Are Most Effective:

  • In high SBRM population areas (especially in Pembina and Walsh counties).
  • If low rates of planting time insecticide were used in high population areas
  • If very heavy rainfall is received after planting beets early.
  • When they are properly incorporated.
  • If rainfall of .5” or more fully activates the insecticide.

Resistant Kochia Management:

Resistant Kochia has become the worst weed problem for American Crystal shareholders.

Fifty Six Percent of ACSC Growers Rated Kochia as the Worst Weed Problem in 2000.

The key to attaining good Kochia control in sugarbeets is controlling it effectively in other crops in the rotation. The University of Nebraska data in Table 1 indicates how viable Kochia seed in the soil can be reduced by up to 98% when buried for only 2 years. Seed was buried 8” deep in the soil. Rainfall at Lincoln was 29” at Mitchell, 13 inches.

YearLincolnMitchell
% Germination
0 100 100
1 0 8
2 2 2
3 0 1

Control Kochia in the Rotation By:

  • Effective preplant tillage and cultivation
  • Use of non-ALS herbicides
  • Use multiple herbicide applications if necessary
  • Raising Roundup and Liberty resistant crops

Field Measurement Update:

Agriculturists and summer scouts have been very busy measuring fields. Well over 60% of the fields in the Crookston districts have already been measured. Measuring is from 30 to about 50% completed in Hillsboro, Moorhead, East Grand Forks and the Drayton district. Susan Sylvester’s name was inadvertently omitted from the measuring team members recognized in an earlier Ag Notes. She is a technical writer who wrote standard operating procedures for the measurement team.

Your agriculturist is surveying SBRM populations and can provide assistance determining when to apply more insecticide

The best time to apply second applications of granules is in late May or early June. The optimum time to apply liquid insecticides is within 3 days of peak fly activity.

Tank mix microrates and liquid insecticides to save costs. This tank mix is safe on the crop at recommended use rates.