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.
![Figure 1 Figure 1](https://rvpadmin.cce.cornell.edu/images/submission/95aa082d463308a2273c437e1c58eee5.jpeg)
![Figure 2 Figure 2](https://rvpadmin.cce.cornell.edu/images/submission/d6c0814a0ffa18cf6d5843dabe86a314.jpeg)
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Upcoming Events
ENY Orchard Soil Health and Beneficial Fungi Meeting
August 15, 2024 : ENY Orchard Soil Health and Beneficial Fungi Meeting
Peru, NY
Join the members of CCE ENYCHP and the Cornell Soil Health Program for a field meeting on the basics of soil health, the potential benefits of mycorrhizal fungi, and an update on the current project status of our SARE grant on orchard mycorrhizal products.
This meeting is intended for farmworkers, young and beginning orchardists, and experienced orchard managers wanting to learn about the basics of soil health and mycorrhizal fungi within the orchard.
North Point Community Farm Twilight Meeting
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August 19, 2024 : North Point Community Farm Twilight Meeting
Plattsburgh, NY
North Point Community Farm Twilight Meeting
Monday, August 19th 4-7 pm (rain or shine)
2172 Military Turnpike, Plattsburgh, NY 12901
$10 per farm
Join us for a tour of North Point Community Farm, a diversified vegetable, berry, and flower operation in the North Country. Farmers Marisa and Mike will give us an overview of their decision-making as they expand their business, increasing their high tunnel production, investing in new tillage equipment, and transforming an old dairy barn into an efficient wash-pack shed with food safety in mind. We'll end the evening with local food refreshments and an opportunity to network with growers from NY and VT.
DEC credits: 1.5 credits in categories 1A, 10, 23
Late Summer Orchard Meeting
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August 21, 2024
Fonda, NY
Join us for our last get together of the summer before we're in the thick of harvest. At this meeting, we will tour Sand Flats Orchard with manager Mitch Hoffman, and we will then discuss late season pest management tasks with our experts from the HVRL and Cornell AgriTech.
DEC Credits: 1.5 credits in categories 1A, 10, and 22.