(2005) evaluated Ca sulfate spray applications and reported that disease severity decreased as Ca concentration of the spray solution increased from 0 to 800 mg⋅L –1 Ca. All Ca sources provided reductions in Botrytis blight severity at 5 mg⋅L –1 Ca however, Ca chloride was the only source effective at 250 mg⋅L –1 Ca. Álvarez (2012) evaluated three sources of Ca on flowers and stems of cut rose ( Rosa × hybrida): Ca chloride, Ca oxide, and Ca amino acid chelate at concentrations up to 1000 mg⋅L –1 Ca. Increasing Ca in the nutrient solution does not provide adequate Ca distribution to low-transpiring plant tissues, such as petunia flowers, whereas spray applications increase the Ca concentration significantly and reduce the disease severity in flower petal tissues ( Bennett et al. Fruit and flowers are supplied mainly with nutrients through the phloem, where Ca transport is low.

Transpiration drives water movement through the plant, supplying the plant tissues with Ca ( White and Broadley 2003) however, transpiration rates of flowers and fruit are relatively low because of their large volume-to-surface area ratio and/or low stomatal density ( Marschner 2012). Calcium uptake from the soil solution occurs from the mass flow of water. Calcium is also involved in intracellular cation–anion balance and acts as a secondary messenger during stress events ( Marschner 2012). 2020b).Ĭalcium (Ca) is a key component in cell wall formation for stabilization and strength, with a high portion of the total Ca located in the cell walls. Symptoms of Botrytis blight typically occur as tan necrotic spotting on the flower petals that coalesce as the disease progresses, resulting eventually in the complete collapse of the flower petal tissue ( Bennett et al. Latent infections may occur during shipping where botrytis spores have infected plant tissue in the greenhouse but remain quiescent until the environment is ideal for sporulation ( Muñoz et al. This situation creates a high-relative humidity environment conducive to the development of Botrytis blight ( Samarakoon et al. Plants are typically irrigated immediately before shipping, then are packed tightly onto shipping carts and loaded into trucks. Botrytis blight is a significant issue during transportation of bedding plants to the retail environment, which may take up to 2 d. When flowers are present on bedding plants, such as petunia ( Petunia × hybrida), botrytis infects the flowers rapidly under conducive environmental conditions, resulting in the disease referred to as Botrytis blight or gray mold. Bedding plant producers experience problems with Botrytis blight in all stages of production, from propagation to postproduction. Keywords: bedding plants Botrytis cinerea disease management gray mold Petunia ×hybrida phytotoxicityīotrytis ( Botrytis cinerea), a necrotrophic plant pathogen, infects more than 200 hosts worldwide, causing significant losses within agricultural systems ( Williamson et al. The results demonstrate that several Ca sources reduce Botrytis blight severity significantly however, selection of the Ca source is important for minimizing the risk of spray damage. Spray damage to the flowers from the Ca chloride application increased when Ca concentrations increased to 2000 mg⋅L –1, but no additional benefit was observed for reducing Botrytis blight severity compared with the 1250-mg⋅L –1 Ca application.

Laboratory-grade and commercial-grade Ca chloride at 1250 mg⋅L –1 Ca were the most effective Ca sources evaluated for decreasing Botrytis blight severity while not causing spray damage at any flower age. For the evaluation of Botrytis blight efficacy, flowers were excised and inoculated with botrytis spores 24 hours after the Ca spray application, and were evaluated every 12 hours for 72 hours. For both experiments, treatments were applied to flowering plants.

In the second experiment, petunia flowers that were 0, 1, 3, 5, or 7 days old at the time of the Ca spray applications were evaluated for spray damage severity. In the first experiment, the six Ca sources evaluated were laboratory-grade and commercial-grade Ca chloride, Ca nitrate, Ca ethylenediaminetetraacetic acid chelate, Ca amino acid chelate, and Ca silicate. This study examines the effects of six Ca sources for their efficacy in reducing Botrytis blight on petunia flowers and their potential to cause spray damage or phytotoxicity. Previous studies have demonstrated the efficacy of calcium (Ca) spray applications derived from Ca chloride for reducing botrytis ( Botrytis cinerea) infection severity on petunia ( Petunia × hybrida) flowers.

Rose botrytis blight edu