Updated April 27, 2021:
Soybean seed treatments have become an integral part of a commercial soybean production system as protection against early season diseases. These include the damping off diseases which are responsible for upwards of $30 million/yr in yield losses in the state of Missouri. Understanding how they fit into the production agriculture system is the key to their continued use.
A total of nine fungicide seed treatment trials were implemented throughout the state with two trials lost due to replant. Five paired treatment strips of fungicide + insecticide vs. naked seed were laid out across each field site. All fungicide + insecticide seed treatment chemicals were chosen by the cooperating partner. Each strip was scouted for early season disease at three and six weeks after soybean emergence. Stand counts were conducted to evaluate losses attributed to these early season “damping off” diseases. In addition to ground scouting, aerial imagery was collected for the same scouting point where stand counts were conducted to document potential differences between treatments.
With a wet spring and early summer, early season disease pressure was high in many fields with conditions being ideal
for disease development. As a result, high levels of early season disease in two fields resulted in trial loss. Of the seven remaining sites, the addition of a fungicide + insecticide seed treatment increased total plant population between 2,000 and 10,000 plants per acre. Positive differences in yield response with and without a seed treatment ranged from 1 to 12 bushels per acre. In more than one field, the addition of a seed treatment did not result in a statistically significant increase in yield.
This season was ideal for the development of early season disease, and this study showed the importance of using
fungicide + insecticide seed treatments to protect against early season diseases in fields where stand loss was observed. This early season protection can also help to reduce weed pressure by reducing bare spots in fields and promoting timely row closure.