Evaluation of Biorational Products for Botrytis Blight Management in Floriculture Crops

The use of biorational products offers an alternative to the conventional chemical fungicide approach to manage botrytis blight caused by Botrytis cinerea . Biorationals are a broad category of products that include biological control agents (BCAs), biologically derived products, compounds that induce natural plant disease resistance mechanisms, and mineral elements. We evaluated 15 biorational products and two chemical fungicides on detached petunia ( Petunia × hybrida ) and rose ( Rosa × hybrida ) flowers inoculated with B. cinerea spores following treatments. The two chemical fungicides, Miravis Prime and Captan, were evaluated as commercial control. In the first experiment, five products showed a reduction in disease severity in petunia flowers (reduction percentages shown in parentheses are relative to the inoculated control): Zivion, a formulation of natamycin, a natural fermentation product of Streptomyces natalensis (66%); ON-Gard Calcium, a calcium chloride product delivered in soy protein (79%); Howler, a formulation of Pseudomonas chlororaphis strain AFS009 (51%); Affirm, a polyoxin D zinc salt (36%); and Regalia, an extract from giant knotweed ( Reynoutria sachalinensis ) (36%). In the second experiment, the five effective products were applied to petunia flowers individually and in combinations. The combination of Zivion + Howler and ON-Gard Calcium + Howler reduced disease severity by 77% and 79%, respectively, compared with the inoculated control, whereas ON-Gard Calcium + Zivion showed a 91% reduction in disease severity. In the third experiment, the same 15 biorational products from the first experiment were applied as a dip application on rose flowers. Applications were made 1 or 8 days before inoculation with B. cinerea spores . When biorational products were applied 1 day before inoculation, Affirm, ON-Gard Calcium, Actigard (acibenzolar-S-methyl, an inducer of systemic-acquired resistance, and Zivion showed a reduction in disease severity of 63%, 33%, 23%, and 18%, respectively. When the biorational products were applied 8 days before inoculation, Actigard, Affirm, and ON-Gard Calcium showed a reduction in botrytis severity by 16%, 54%, and 31%, respectively. In the fourth experiment, the four most effective products were evaluated as single and combination applications on rose flowers. The combinations of Actigard + ON-Gard Calcium, ON-Gard Calcium + Zivion, and Actigard + Zivion reduced botrytis blight by 66%, 62%, and 53%, respectively, whereas Actigard + Affirm, ON-Gard Calcium + Affirm, and Zivion + Affirm reduced disease severity by 85%, 77%, and 76%, respectively. This work demonstrates that tank mixes of biorational products, which provide different modes of action, can have comparable efficacy to chemical fungicides for controlling botrytis blight in petunia and rose flowers.