Effectiveness of Contans and Serenade Within a Biologically Intensive Integrated Pest Management System for Sclerotinia Drop on Lettuce: 2005 Study

Abstract

Sclerotinia drop of lettuce, caused by the pathogenic fungi Sclerotinia minor and S. sclerotiorum, is a serious disease in most regions where this crop is grown. Conventional fungicides, such as Rovral (iprodione) and Endura (boscalid), are usually applied after lettuce is thinned and once more 2 to 3 weeks later. Two biological products, Contans (Coniothyrium minitans) and Serenade (Bacillus subtilis), are also available. In earlier field trials conducted from 2001 to 2003 in the presence of S. sclerotiorum, the mean reduction in disease by Contans, Serenade and Endura was 69, 18 and 41%, respectively. The objective of the current study was to determine the efficacy of the biological products Contans and Serenade, applied alone or in combination with each other or the conventional fungicide Endura, within a biologically intensive integrated pest management system for Sclerotinia drop on lettuce. The study was conducted at The University of Arizona, Yuma Valley Agricultural Center. Sclerotia of Sclerotinia sclerotiorum were produced in the laboratory. Lettuce ‘Winterhaven’ was seeded and sclerotia were applied to the plots on November 8, 2004. Disease assessment was performed three times, including plant maturity (February 24), by recording the number of dead plants in each plot. Lettuce drop caused by Sclerotinia sclerotiorum was significantly reduced by the biofungicides Contans and Serenade as well as the conventional fungicide Endura. At plant maturity, the highest level of disease control among all treatments was provided by one or two applications of the biofungicide Contans as well as application of Contans at seeding following by either Serenade or Endura after thinning. Also, two applications of the other tested biofungicide, Serenade, controlled Sclerotinia drop as well as two applications of the conventional fungicide, Endura. The results of this study suggest that the biological products Contans and Serenade, used either alone or with the conventional fungicide Endura, can provide effective levels of control of lettuce drop caused by S. sclerotiorum. Although encouraging, the results from this initial field trial will need to be confirmed by additional studies. Funding for this research project was provided, in part, by the IR-4 project under a cooperative agreement with the U.S. Environmental Protection Agency.