Cultural Control

Cultural control of the disease involves strategies for reducing soil sclerotial populations. Crop rotation to non-hosts can reduce soil populations of sclerotia, but the selection of rotation crop must be carefully selected as both causal agents have wide host ranges. Deep inversion plowing can be used occasionally to move the inoculum deeper into the soil profile. Summer flood solarization has been shown to reduce sclerotial populations in desert production areas. Irrigation management also is effective with drip irrigation resulting in the lowest incidence of disease.

Chemical Control

There are a number of fungicides that are effective against lettuce drop; iprodione, boscolid, dicloran, and others. Most are applied at the rosette stage in banded application targeting the base of the lettuce plant.  For control of S. minor, additional applications post-thinning are effective. Before using any product to control lettuce drop, check product labels and restrictions and consult with your local Extension Specialists and Pest Control Advisers.

Biological Control

Considerable research has been conducted on evaluating biological control agents to manage Sclerotinia disease in a number of cropping systems. Trichoderma spp., Sporidesmium sclerotivorum, and Bacillus subtilis have been evaluated against Sclerotinia spp. but have not performed well under field conditions (Chitrampalam et al 2008, Plant Dis. 92:1625-1634).

In striking contrast, Coniothyrium minitans has shown much higher efficacy. Two applications of the recommended rate of C. minitans (Contans) (2lb /acre)one at planting and one at post thinning outperformed commonly used chemical fungicide Rovral (Iprodione) for controlling lettuce drop caused by S. sclerotiorum. However, C. minitans had less effect on S. minor (Chitrampalam et al 2008, Plant Dis. 92:1625-1634).