Effect of Biofumigation and Soil Solarization on Sclerotinia sclerotiorum in High Tunnel Vegetable Production Systems of Kentucky Brian Geier Michael Bomford Paul Vincelli George Antonious
Production System: High Tunnels High Tunnels ( hoophouses ) are unheated greenhouses used by growers to extend the growing season.
Production System: High Tunnels
Production System: High Tunnels What is grown in high tunnels? Early and late vegetables: tomatoes in May or October Winter greens: lettuce, mustards Winter vegetables: beets, carrots, radish Early or late fruits: brambles, strawberry Seedlings or nursery plants
Production System: High Tunnels Disease is the #1 problem. Sclerotinia sclerotiorum Soil-borne disease Broad spectrum Favors cool, moist conditions -Paul Wiediger, high tunnel grower, Smith s Grove, Kentucky
Soil Borne Disease Management Tactics Suitable for certified organic farm fields and high tunnels Biofumigation: uses natural chemicals of brassicas, glucosinolates, to suppress soil-dwelling pests. Soil Solarization: soil is covered with clear plastic, and heated to temperatures that are lethal to pest organisms.
Testing the Effect of Biofumigation and Soil Solarization on Sclerotinia sclerotiorum in a High Tunnel at the Kentucky State University Research Farm 16 4x8 plots inside a high tunnel 8 planted with Biofumigant crop: Pacific Gold Mustard 8 planted with non- Biofumigant crop: Buckwheat (control) Sclerotia grown and bagged in the lab Placed in soil at 0,5,10, and 15 cm depths, in each plot, for duration of study
Testing Biofumigation and Soil Solarization in a High Tunnel at the Kentucky State University Research Farm Rate of Biofumigation: 606g/m 2 Target Rate Based on Exposure Studies: 16kg/m 2 Less than 4% of target rate.
Testing Biofumigation and Soil Solarization in a High Tunnel at the Kentucky State University Research Farm
Testing Biofumigation and Soil Solarization in a High Tunnel at the Kentucky State University Research Farm
Testing Biofumigation and Soil Solarization in a High Tunnel at the Kentucky State University Research Farm Bags of sclerotia removed after 48 hours and 4 weeks of treatment. Sclerotia plated onto sterile soil and incubated. Germination counts performed to assess survival.
Results Viable sclerotia proportion Depth (cm)
Results 0 5 10 15 5-from planting Depth (cm) 0 510 15 5-from planting 1 0.8 0.6 0.4 0.2 0 Viable sclerotia proportion
12:00:00 AM 2:00:00 AM 4:00:00 AM 6:00:00 AM 8:00:00 AM 10:00:00 AM 12:00:00 PM 2:00:00 PM 4:00:00 PM 6:00:00 PM 8:00:00 PM 10:00:00 PM Average Hourly Drop Page Soil Fields Here Temperatures Soil Temperature Average of Avg Temperature (C) 50 45 40 35 30 25 20 15 10 5 0 Treatment Outdoor Soil Unsolarized Solarized Outdoor Soil Time of Day Time
140 131 122 60 55 50 Soil Temp. 113 F C 104 45 40 95 86 77 35 30 25 8:00 PM 3:00:00 PM 10:00 AM 5:00 AM 12:00 AM 15 10 5 0 15 10 5 0 Depth (cm) SolarizedControl
Number of Germinating Sclerotia (of 40) after 6 Weeks in the Soil
Looking Ahead: What We Know, What We Don t about Biofumigation, Soil Solarization, and Soil-borne Diseases in Kentucky We Know: Soil Solarization, where temperatures remain around 30 C for a 6 week period, is very effective at killing sclerotia of S. sclerotiorum. At 4 weeks, the effect is significantly less. We Know: Biofumigation, by methods of growing Pacific Gold Mustards, chopping biomass finely at flowering, and immediately incorporating into soils, has not shown an effect on the survival of bagged sclerotia. We Know: S. sclerotiorum and Phytophthora capcisi exhibit lower survival rates after exposure to higher concentrations of glucosinolate extracts taken from Pacific Gold Mustards. We Don t Know: How age/life stage or exposure to soil effects the susceptibility of sclerotia to solarization or biofumigation. We Don t Know: How to grow, chop, and incorporate Mustard cover crops in a way that exposes bags of S. sclerotiorum to lethal concentrations of glucosinolates. We Don t Know: Why growers saw a reduction in S. sclerotiorum damage following Pacific Gold cover crops glucosinolate exposure, increased organic matter, disruption by tillage, etc.?