Protecting sugarbeet seedlings from disease
Common sugarbeet seedling diseases in Michigan can include Rhizoctonia, Aphanomyces, Fusarium, Pythium and Phoma.
Diseased sugarbeet seedlings have been sampled in the last four years by pathologist Dr. Linda Hanson of USDA Agricultural Research Service. This study has been conducted since 2008 with the collection of three to eight diseased plants per field in a varying number of fields depending on disease pressure. Depending on the environmental conditions, the predominate pathogen varied between years. The three most isolated pathogens included Rhizoctonia (both AG-4 and AG-2-2), Aphanomyces, and Fusarium. Pythium and Phoma where isolated less often. Most of these these diseases can kill seedlings by damping off or greatly affect the growth of plants.
Some of our varieties have resistance to diseases such as Rhizoctonia or Aphanomyces, but do not exhibit the resistance at the seedling stage of growth. Prediction of specific seedling diseases is not possible until after planting, and any prediction is then based on environmental conditions. Protecting against seedling disease must occur as a seed treatment or with in-furrow applications of protectants. Currently our standard seed treatment is metalaxyl, which protects us primarily from Pythium and has little or no effect on the other diseases.
We do have some options that can be used in conjunction with the standard seed treatment. The first is Tachigaren, which can be applied as a seed treatment and will help control Aphanomyces, a problem associated with warm, wet springs. Growers may also consider applying Quadris in a T-band in-furrow for control of Rhizoctonia. This will not only control the seedling phase but also help later to prevent root rot.
There are several new seed treatments that have recently been approved. Most of these products are being field evaluated and hold some promise in controlling the complex of seedling diseases we have in Michigan. It is hoped that some of the new seed treatments may be helpful in the future for Rhizoctonia and Fusarium.