23 SCBG-UKRF-Lettuce Growers

Resistant Cultivars and Time of Planting as a Fungicide-Free Option for Management of Lettuce Drop in High Tunnels in Kentucky High tunnels are most often utilized for production of high profit specialty crops, and they are particularly profitable when used to extend the growing season in early spring and late fall. Of course, this profitability is dependent on crop timing, cultivar selection, and pest and disease management. According to a January 2022 grower survey, diseases caused by Sclerotinia sclerotiorum are the top concern for high tunnel producers. Without fallow periods or a 3-year rotation with a non-host, the fungus multiplies and increases in soil. Losses can be especially severe in high tunnels because of the intensive cropping system and limited options for non-host rotations. If not managed, S. sclerotiorum can result in high tunnels that become unusable (and unprofitable) within a few years. Lettuce drop, a destructive disease of lettuce caused by S. sclerotiorum, infects and destroys lettuce crops between mid- April and mid-May as soil temperatures warm or between early-October and early-November as soils cool. This is also the time when farmers markets are experiencing increased demand, and lettuce prices are at their peak. Cultural practices such as using resistant cultivars and early/late planting are techniques that are already applied to other cropping systems in the northern US and Canada and have huge potential for cool season lettuce in Kentucky high tunnels. These practices have yet to be tested in Kentucky or under environments where optimal conditions for S. sclerotiorum occur in early spring or late fall in high tunnels. As growers face the challenges of increased pressure from soilborne fungi such as S. sclerotiorum and financial demands that require succession planting (or intercropping) for increased profits, they are in need of a practical, economical solution to this perennial problem. Furthermore, many growers cannot afford specialty fungicides, or their production practices do not allow for application of conventional fungicides (e.g. certified organic growers). The objectives of this project align with expressed grower needs. The aim of this study is to examine a range of cultural practices for production of spring and fall lettuce in Sclerotinia-infested high tunnels. Objectives include: 1) Evaluate disease development on lettuce treated under different cultural practices: resistant cultivars, early planting, and decreased soil moisture (Year 1 and 2); 2) Compare yield, quality, and potential profits of lettuce from different cultivars, different planting times, and reduced water (Year 1 and 2); 3) Develop grower resources for spring and fall high tunnel lettuce production (Year 2 and 3). Research data from Objectives 1 and 2 will be used to develop a production guide for high tunnel lettuce, a train- the-trainer workshop for county extension agents, and a demonstration how-to video reference for growers.