With multiple rain delays slowing the progress of wheat harvest, some areas of the state are reporting sooty molds and grain with a discoloration known as black point. Both of these problems are caused by molds that grow on the mature wheat.
These molds are normally not aggressive pathogens in wheat, but they can rapidly colonize mature plants. These diseases are most problematic when rain re-wets mature plants and causes harvest delays. The sooty molds are often a cosmetic problem because the mold growth is very superficial on the chaff and glumes. The sooty molds can make for a dusty harvest, however. If the timing of the rain coincides with the late stages of kernel development, the molds can begin to colonize the outer layers of the wheat kernel, resulting in a gray-black discoloration called black point. Commonly, the embryo end of the kernel is most discolored, but entire kernels can become gray or black as result of the black point.
There is no management of these diseases at this time. The fungi that cause black point can cause problems with germination and reduce seedling vigor. Therefore, seed lots with symptoms of black point should be tested for germination. If black point is causing germination problems, fungicide seed treatments can often improve the germination and ensure good stand establishment.
Figure 1. Wheat head with symptoms of sooty mold. Photo by Erick DeWolf, K-State Research and Extension.
Figure 2. Wheat kernels with symptoms of black point (top row of kernels is healthy). Photo by Erick DeWolf, K-State Research and Extension.
Erick De Wolf, Extension Plant Pathology