By Adriana Murillo-Williams and Paul D. Esker er.al
What are the conditions that favor stem diseases?
Weather drives plant disease development. While many regions in Pennsylvania continue experiencing a precipitation deficit that keeps soybean foliar diseases at bay, the situation differs for stem diseases, with reports of sudden death syndrome, anthracnose, and white mold in different parts of the Commonwealth. If conditions have been so dry, why are these diseases occurring? Microclimate variability can be very high, even within the same field, and conditions within the canopy may vary greatly in terms of temperature and humidity compared to open air. Therefore, a single shower or a thunderstorm may provide the right conditions for infection and disease development.
Sudden death syndrome (SDS)
During the Spring, many areas around Pennsylvania received above-average precipitation. The pathogen (Fusarium virguliforme) survives from season to season in the form of survival structures called chlamydospores. It infects seedlings through the roots early in the season when conditions are cool and wet. Infection is favored by soybean cyst nematode (SCN) infestations. Although infection occurs in the Spring, the symptoms develop during the reproductive stages and start as an interveinal chlorosis that becomes necrotic, leading to leaf death (Figure 1).