Postharvest calcium chloride dips. An effective strategy to reduce Botrytis blight severity and increase petal strength in cut roses.

Botrytis blight in cut-flower roses is a devastating disease caused by Botrytis cinerea. Calcium (Ca) applications have shown great potential as alternative disease management strategies for different crops. This research aimed to evaluate the effect of preharvest calcium sprays and postharvest calcium dips on rose flower susceptibility to Botrytis blight, petal tissue calcium concentration, and petal strength. Calcium chloride spray applications (0, 500, 1000, and 1500 mg^.L⁻¹of Ca) during greenhouse production and postharvest calcium chloride dips (0, 1000, and 2000 mg^.L⁻¹ of Ca) were evaluated and compared with commercial controls, including hydrogen peroxide, captan, and pydiflumethophen + fludioxonil. Calcium chloride sprays during production reduced Botrytis blight severity at 500 and 1000 mg^.L⁻¹ of Ca; however, no concentration of calcium chloride spray solution increased calcium in the petal tissue. Postharvest calcium chloride dip applications at 1000 and 2000 mg^.L⁻¹ of Ca effectively reduced Botrytis blight compared to the untreated control. Calcium chloride dip applications at 2000 mg^.L⁻¹ of Ca were effective for increasing the calcium concentration in the epidermis and mesophyll of the petal tissue in comparison to the 0 mg^.L⁻¹ treatment and resulted in increased petal strength and reduced Botrytis severity in comparison to captan and hydrogen peroxide treatments. These results show that postharvest calcium chloride dip applications are more effective than spray applications during production in improving calcium concentration and petal strength on roses and result in a reduction of Botrytis blight severity greater than captan and hydrogen peroxide commercial treatments. This underscores the importance of calcium chloride applications as an alternative management approach for Botrytis blight on roses.