Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
Overall, there has been little disease pressure in soybeans this year. The wet conditions of last fall led to quite a few late season soybean pod and seed quality issues in 2018. With the continued dry weather in the forecast, it is unlikely that pod and seed diseases will be an issue this season. Just in case there is a sudden change in the forecast, we will discuss a few of the common pod and seed issues.
Purple Seed Stain
As the name implies, symptoms of this disease include seeds with a pink to dark purple discoloration. Caused by the fungal pathogen Cercospora kikuchii, infection can affect seed quality and appearance, but does not typically decrease yields.
Figure 1: Purple seed stain
Phomopsis Seed Decay
Caused by the fungus Diaporthe longicolla (syn. Phomposis longicolla), infected seed is shriveled, cracked, and often has a chalky to white appearance. Emergence and seedling blight issues are common when planting infected seeds. Fungicide seed treatments are generally effective against Phomopsis seed infection, but it is still best to plant seed with a low occurrence of Phomopsis seed decay to ensure optimal stands.
Figure 2: Seed with a cracked, shriveled appearance and covered with chalky to white mold may have Phomopsis seed decay
Anthracnose
Anthracnose in soybean is caused by the fungal pathogen Colletotrichum. Symptoms can be present on the stems, leaves, or pods. Pods that become infected often have reduced or no seed formation and the pod may be filled with fungal mycelium. Seed that does from is usually shriveled, moldy, and discolored.