Wet soils have caused a high amount of sugarbeet seedling disease
Sugarbeet seedling disease levels are high in 2013 due to late planting and excessive rainfall in Michigan.
Many Michigan sugarbeet producers are experiencing a heavy amount of sugarbeet seedling disease this year (2013). Excessive rainfall this spring has caused later than normal planting and relatively warm soils. This combination has produced a complex of seedling diseases that are affecting roots and causing die off of small plants. Some areas have experienced greater than 5 inches of rainfall in one week. Saturated soils on emerging and established young plants can and will allow a complex of root pathogens to flourish. These diseases will include Pythium, Rhizoctonia, Aphanomycetes and Fusarium. These diseases can cause varying levels of damage including death of the plants.
Sugarbeet fields that were planted in early April have survived the onslaught of water much better than sugarbeets planted in May. The early planted sugarbeets appear to be growing relatively fast and some fields will be canopied in the next couple weeks. In contrast, the May sugarbeets are in what may be called a “recovery mode.” Many of these sugarbeets are much smaller than normal and have damaged roots. A good share of the root damage appears to be Aphanomyces which will constrict the root and cause it to hang on by a thread. These plants often will die, tip over, and when windy get blown to the center of the row. Depending on the severity, many can recover to varying degrees, but will have scared roots and reduced yield and quality.
Tachigaron applied at the 20 gram rate to the seed can give some control of Aphanomyces, but the higher 45 gram rate will be better under severe conditions. Very little seed is treated at the 45 gram rate because it has been shown that it may reduce emergence. A large share of the Michigan seed this year was treated at the 20 gram rate and should have been helpful. At this point, there is nothing a grower can apply that will help the situation. We have been very fortunate that cooler conditions have been with us for the past couple weeks, allowing the plants to survive. Under hot, dry and windy conditions, plant mortality would be much higher.
The second most common seedling disease seen was Rhizoctonia. Symptoms can be similar, but usually a dark brown lesion will begin just below the soil surface and extends up to the hypocotyl. Often a sharp line will exist between diseased and healthy tissue. We have seen in past Michigan State University Extension Sugarbeet Advancement trials, growers that use Quadris T-band in-furrow will have better stands by controlling the seedling Rhizoctonia.
Growers will need to be aware that seedling diseases that damage roots can increase the incidence of root rots later in the season. We know this to be particularly true when it comes to Rhizoctonia. A full rate of Quadris applied in a 7-inch band at the 6-8 leaf stage can help reduce the incidence of Rhizoctonia. However, this fungicide does not last the entire season and has no effect on Aphanomyces or Fusarium. It is difficult at this time to predict the total outcome of the late planting and seedling disease issues.