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
2025 New York State Potato School

February 11 - February 12, 2025
Waterloo, NY
This year's program will feature speakers covering critically important topics like disease management, updates in storage techniques, new varieties, and other production management practices. New for this year will be the Processor Panel where guests will have the chance to interact with some of the major chip processors in the northeast. Your participation will also earn you DEC and CCA points.
Remote Good Agricultural Practices (GAPs) Training
February 12, 2025
Join Cornell Cooperative Extension of Orange and Oneida Counties, the Cornell Vegetable Program, Harvest NY, and the Eastern NY Horticulture Team on Feb. 12 for a remote Good Agricultural Practices (GAPs) training. Good Agricultural Practices is a voluntary food safety audit program requiring minimum standards for the production, handling, packing, and storing of fresh fruits and vegetables, and is required by some buyers. Trainers will cover food safety best management practices related to worker training, preharvest assessments and wildlife management, water testing, postharvest handling, hygienic equipment design and efficient wash-pack setups, how to write a farm food safety plan, and more. The training will follow the USDA GAPs audit checklist so that farms will be prepared for an audit. A NYSDAM GAPs auditor will join us to discuss audit logistics and answer questions from participants. Following the course, we will offer a series of virtual office hours to follow up with course participants to assist them with writing their farm food safety plan, which is mandatory for the GAPs audit. Participants will receive a certificate of course completion after the training.
Food Safety Lunch and Learn Webinar Series
February 11, 2025 : Part One: What's Going on with Food Safety?
NYS Department of Agriculture and Markets FSMA inspectors are expected to step up farm visits this season. Why are they showing up on the farm asking about FSMA? Aren't we exempt? This noontime hour we will discuss the purpose of the farm visits and what produce farmers need to know.
February 18, 2025 : Part Two: What Counts as Food Processing?
In this session, we will discuss what counts as processing and what doesn't. Stories of inspectors coming to farmers markets and auctions telling some growers certain products can't be sold usually without much explanation. We will try to make some sense of things and clear up some misunderstandings so hopefully the upcoming season goes smoothly.
February 25, 2025 : Part Three: Traceability - Benefits for Food Safety and Beyond
Can having a traceback process for your produce (and other farm products) make good business sense regardless of FSMA regulations? We will (try to) make the case for farms to have some sort of traceability mechanism in place.