2018 ASHS Annual Conference

Spray applications of calcium applied to petunia plants improve the resistance of petunia (Petunia xhybrida) flower petals to Botrytis cinerea infection. The objective of this experiment was to evaluate the effect of various calcium sources for Botrytis control and their potential phytotoxicity. Products examined included, calcium chloride, calcium silicate, potassium silicate, calcium EDTA, calcium nitrate, and calcium metalosate. Three application rates were chosen for each calcium source. A 1-5 scale was used to evaluate spray damage on petunia flowers (1=no damage; 5=75-100% damage). Flower bleaching (pigment loss) was evaluated on a 1-3 scale (1=no bleaching; 3=severe pigment loss). Flowers were treated at different stages of development (buds and 1, 3, 5 and 7 d old open flowers prior to treatment). After the single spray application of the calcium treatments, flowers were then rated 1, 3, 5, and 7 d after the spray. Three to 5 day old flowers were the most susceptible to spray damage, whereas buds were the least susceptible. Calcium chloride and calcium nitrate had the least amount of spray damage and flower bleaching, while potassium silicate and calcium EDTA had the most. Once all the opened flowers had died, the plants returned to a normal appearance except for the higher rates of calcium EDTA which continued to produce damaged flowers for several days after the treatment. Botrytis efficacy trials were conducted to determine which nutrient sources provided the most disease control.