Evaluate sugarbeet fields in August to determine production issues in the future

Many sugarbeet yield-limiting factors can be determined in August by evaluating each field. Management practices can be implemented in future rotations to avoid the same issues.

August is a great time to evaluate sugarbeet fields for yield-limiting factors. Because sugarbeet rotations are relatively long (three to four years), trying to commit this information to memory may lead to critical issues being forgotten. This information should be filed for future reference on a field-by-field basis for the next time sugarbeets are grown. It is important that both above and below ground examination be completed. Management strategies then can be developed to minimize future production issues.

The process should start with a general overview of the field. Make note of areas that are off color, wilting or lack canopy. These areas will need to be examined in more depth to determine the cause. Many above ground symptoms are the result of poor root growth or things that are happening to the root. Using a shovel, roots should be carefully dug up so that they can be examined. If roots are sprangled, this is often the result of compaction or sugarbeet cyst nematodes. Examine the hair roots for tiny cysts that are often visible at this time of the year. Even if sugarbeet cyst nematodes are not seen, a soil sample should be taken and sent to the MSU Diagnostic Services Lab for a nematode test. Sugarbeet cyst nematodes can cause a host of maladies in sugarbeets ranging from nutrient deficiencies, wilting and overall poor plant growth. If nematodes are found, utilize resistant varieties in rotation.

Pay particular attention to any root diseases. Rhizoctonia can occur as crown rot, tip rot or as black rotted areas on the side of beet roots. Rhizoctonia can greatly reduce yield and sugarbeet quality. Aphanomycetes can also cause deformity and a scabby scaring appearance on the roots. Often, these disease issues and poor rot growth tend to be worse between tile lines, which would indicate a need for improved drainage. If these diseases are significant, then use resistant varieties, chemical control or a combination of the two the next time beets are in this field. Chemical control for Rhizoctonia would be Quadris applied either in furrow or foliar. For Aphanomycetes, use Tachigaren seed treatment. Chemical controls are not 100 percent effective and trying to address large problems only using chemical control is risky.

Evaluate the level of Cercospora leaf spot on foliage. Finding more than an occasional spot would indicate a problem with the control strategy. Problems could result from several factors including using a strobilurin fungicide alone in a field with strobilurin resistant leaf spot. Other possible reasons for problems could have been from incorrect application timing (DSV), poor water pressure and volume, or stretched reapplication windows. Healthy, disease-free foliage will maximize sugar production. 

In August, foliage still should be green, healthy and canopying the rows. This is an indication nitrogen levels are sufficient. However, as we get into September and October, it is desirable to have foliage become “off green,” indicating soil nitrogen is used up and sugar is being stored. Foliage that is showing any micronutrient deficiency such as manganese or boron should also be noted. This may be an indication that soil levels are low and nutrients may be needed next time beets are grown. However, several other factors could also cause deficiency symptoms, so look for other possible causes such as nematodes, root diseases or compaction layers. Foliar nutrient testing and petiole nitrate testing are very good tools in showing sufficiency levels of nutrients.

It is also important to evaluate the variety used in the field. Varieties have a wide range of disease tolerance; generally, varieties with higher disease tolerance will also have reduced yield and sugar potential. If your fields are 100 percent disease-free, you may be limiting your yield and revenue by not choosing a variety with higher genetic yield potential. Variety trials often show $200 to $500 revenue differences between top and bottom performing varieties within trials. It’s a difficult balancing act.

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