ISSUE #363

363 Aphanomyces Indexing Service Offered


363.1APHANOMYCES COCHLIOIDES is fast becoming a limiting factor in the production of sugarbeets in some areas of the Red River Valley. In several cases, fields that have been in a sugarbeet rotation for years now cannot produce a sugarbeet crop because of the disease pressure exerted by this fungus.

363.2Control of Aphanomyces is not yet possible but management is helpful. Where you expect disease pressure, choosing varieties that show some resistance, using tachigaren pelleted seed and knowing the potential severity in the field through indexing are all important tools in managing your beet health. In addition to that, planting early, cultivating to keep the soil dry, enhancing field drainage, increasing length of rotation, controlling weeds and avoiding the spread of contaminated soil from field to field.

363.3American Crystal is again offering an Aphanomyces Indexing service at no charge to its shareholders. Remember, the accuracy of the index reading that you receive will be no better than the soil sample taken so please follow the soil sampling method as closely as possible.

TAKING THE SAMPLE: we ask that the grower take the sample. You know the field the best.

DELIVERY TO THE DIAGNOSTIC LAB: if you can’t get it to the diagnostic lab, contact your agriculturist. He or she can then arrange delivery.

TESTING PROCEDURE: the soil sample is dried, run through a grinder and then sieved through a *" screen. Five individual pots are planted with 25 seeds/pot using Crystal 261 as the susceptible variety. The pots are placed in a growth chamber for four weeks where temperature and humidity are kept constant at 26 degrees C. and 80% respectively. The pots receive 16 hours of light and 8 hours of dark.

Once the seedlings show signs of damping off, the infected seedlings are removed and taken into the micro lab for root culturing. After positively identifying the disease through microscopy techniques, an indexing number is assigned to the soil sample. The rating is a number from 0 to 100.

ROOT ROT INDEX: What does the root rot index value mean? It is a relative measure of the severity of aphanomyces root rot inoculum in your field. It is based on a disease class rating of seedlings grown in your soil sample.

Disease Classes

0 = Healthy plant
1 = Hypocotyl light brown, water soaked
2 = Hypocotyl brown, moderate amount of rot/constriction, plant not dead
3 = Hypocotyl brown, constricted, plant dead


Root Rot IndexCrop Risk*
0 - 25 Low
25 - 50 Moderate
50 - 75 High
75 - 100 Very High
* Weather conditions determine level of risk and crop loss.

Soil Sampling Method

  1. 20 lbs. of soil per sample minimum.
  2. Samples can be taken at any time during the year.
  3. Each sample should represent the entire field. If you want to split a field we would need two separate samples.
  4. Sampling should be taken at random in at least 6 different locations throughout the field including one high area and one low area.
  5. Only the top 6"s of soil should be collected, nothing deeper.
  6. Samples are to be double bagged in an ordinary grocery bag. NO PLASTIC of any sort should be used.
  7. Labeling: (very important)

    • Date
    • Grower Name
    • Contract Number (if available)
    • Agriculturist Name
    • Legal Description of Field

  8. The sample should then be delivered to the diagnostic lab (Mike Metzger) at Beet Seed located at the Technical Services Center (formerly Research) as soon as possible.

Knowledge of your index reading will help you to develop a management plan. For Aphanomyces to cause disease symptoms, three factors must be met: 1) the disease must be present in the soil, 2) a susceptible crop such as sugarbeets must be at risk and 3) the soil needs to be warm and wet. If you are missing any one of these three factors, Aphanomyces will not be an issue.

Take advantage of this service and have your soil tested.

Eminent Section 18 Granted

Eminent fungicide for Cercospora leaf spot control was granted a section 18 for MN & ND in April. SipCam, the manufacturer indicated it will be priced competitively per day of disease control. More details will follow later.