Phomopsis seed decay (PSD) and purple seed stain (PSS) are two seed-borne diseases that can impact soybean quality. PSD-infested seeds are often lightweight and show reduced germination, whereas PSS infected stain often develops a purple discoloration. PSS also can result in leaf blighting and seedling death in some instances.
Therefore, both PSD and PSS can reduce value of soybean grown for seed or sent overseas. Management of these diseases often is achieved by planting clean, certified seed, crop rotation, deep tillage to bury infested residue, and in very limited situations, fungicide applications between R3 and R5.
Many growers are switching to no-till or conservation-tillage systems, which may influence the severity and incidence of soybean diseases such as PSS and PSD and also impact disease management. Unfortunately, there simply isn’t much out there in terms of replicated, applied research in this area.
Researchers at The University of Tennessee conducted trials over a 4 year span that looked at the impact of tillage and fungicides on PSD or PSS. However, the use of a fungicide reduced PSD in tilled but not no-tilled settings.
In addition,the application of Headline at either R3 or R5 resulted in greater levels of PSS across tillage treatments. Their results were recently published in the journal Crop Protection.