Be on the Lookout for Southern Blight
Ethan Grundberg, Vegetable Specialist
Eastern New York Commercial Horticulture
Southern Blight is caused by the fungal pathogen Sclerotium rolfsii and has historically only been a concern to growers in southern states. However, Cornell pathologist Dr. Sarah Pethybridge has seen an
increase in the incidence of Southern Blight in New York over the past several years. This winter, Dr. Pethybridge confirmed the presence of S. rolfsii on golden storage beets in Dutchess County. Given the broad host range of the pathogen that includes over 1,200 crops and weeds, it is imperative that growers who suspect a possible Southern Blight infestation on their farm contact extension to confirm the diagnosis to assist with optimizing crop rotations to reduce soilborne inoculum.
The most common symptom observed in the field is wilting or collapse of the plant. Upon closer inspection, affected plants often have reddish-brown dry lesions at the soil line. Fungal mycelium is also usually present as a thick white mat around the base of the stem. The Southern Blight pathogen also produces overwintering bodies called sclerotia under the right environmental conditions (typically high humidity with temperatures about 80 °F, but sclerotia were found on beets in cold storage at 40 °F). The sclerotia formed by S. rolfsii are a key identifying feature; they are small balls similar in appearance to Dijon mustard seeds that change in color from white to golden to reddish-brown (see image). These sclerotia can survive in the soil for years and endure temperature extremes and drought while waiting to germinate in the presence of a host plant under the right environmental conditions.
Crops that are most commonly affected by Southern Blight are tomatoes, peppers, snap beans, onions, garlic, and Jerusalem artichokes; however, as indicated above, the pathogen can grow and reproduce on a much broader range of plants. Like with most diseases, early detection and proper identification are critical! Infested plants should be removed and destroyed if possible. Symptomatic plants should NOT be placed in compost, as they may contain sclerotia that will then be spread with the compost to other fields. Some small grains and corn are less susceptible to Southern Blight and can be used in rotation in heavily infested fields, but crop rotation is typically not a viable strategy for management of this pathogen given its broad host range. Initial research in New York suggests that deep plowing of infested fields to bury sclerotia and infested residue at least 6-inches deep can lower the pathogen's survival rate.
Several effective chemical controls are available to conventional growers, but they must be applied preventatively. Labeled formulations of azoxystrobin (Quadris), pyraclostrobin (Cabrio), and penthiopyrad (Fontelis) have been effective for growers in the south. Some research has suggested that OMRI-approved biocontrol agents, such as Trichoderma harzianum (RootShield, TerraGrow) and Gliocladium virens (SoilGard), may also help reduce the number of Southern Blight sclerotia and prevent colonization of host plant tissue by the pathogen.
Upcoming Events
Urban and Small-Scale Growers Meeting
April 5, 2024
Buffalo, NY
This event is an opportunity for small-scale growers, urban growers, community garden leaders and ag service providers to build community, engage in production-focused workshops, and share resources. Topics include building soil productivity, insect and disease management, growing vegetables, berries, and tree fruits, and more.
REGISTRATION IS CLOSED! We met the space limitation for this event.
2024 DEC Special Permit Handler Training -- Wayne County
April 9, 2024
Newark, NY
Special Permits (SP) will relieve the certified pesticide applicator from "on-site within voice contact" supervision of non-certified pesticide applicators when they are handling federally-restricted-use pesticides for which they hold a Special Permit. The 8 specific labels covered: Endigo ZCX, Warrior II with Zeon Technology, Agri-Mek SC, Beseige, Leverage 360, Danitol 2.4EC, Mustang Maxx, and Lannate LV.
2024 DEC Special Permit Handler Training -- Orleans County
April 10, 2024
Albion, NY
Special Permits (SP) will relieve the certified pesticide applicator from "on-site within voice contact" supervision of non-certified pesticide applicators when they are handling federally-restricted-use pesticides for which they hold a Special Permit. The 8 specific labels covered: Endigo ZCX, Warrior II with Zeon Technology, Agri-Mek SC, Beseige, Leverage 360, Danitol 2.4EC, Mustang Maxx, and Lannate LV.