Management of Botrytis cinerea in Petunia Using Cultivar Resistance and Biorational Products

Botrytis cinerea causes blight on the leaves, stems, and flowers of petunia (Petunia x hybrida), a popular annual bedding plant. Our objectives were to evaluate: (i) four standard and nine Wave® petunia cultivars for resistance to Botrytis blight and (ii) ten biorational products compared to the standard fungicide fenhexamid and an untreated control to limit disease. According to the final disease assessment and AUDPC data, ‘Sophistica Blackberry’ had significantly less disease than ‘Tidal Wave® Cherry’ in all trials. ‘Tidal Wave® Cherry’ also had significantly more disease according to ratings and AUDPC data than ‘Easy Wave® Red Improved’, ‘Wave® Purple Classic’, ‘Tidal Wave® Silver’, ‘Shock Wave® Red’ and ‘Easy Wave® Blue’ in trials 1 and 3, whereas in trial 2 these differences were not observed. When evaluated on ‘Shock Wave® Red’ petunia, Prestop (Gliocladium catenulatum) provided significant B. cinerea control and was similar to the fungicide standard Decree (fenhexamid) in both trials. According to the final disease severity assessment, treatment with Botector (Aureobasidium pullulans), Zio (Pseudomonas chlororaphis) or LifeGard (Bacillus mycoides) also provided control similar to the fungicide standard but was significantly different from the untreated control in one trial only. Results from this study illustrate that certain biorational products can limit B. cinerea when used in conjunction with a cultivar that has disease resistance that limits the impact of the pathogen. Keywords: Petunia x hybrida, gray mold, fenhexamid, fungicide