Effects of multiple applications of chemical elicitors on Botrytis cinerea infecting Geraldton waxflower

Geraldton waxflower is susceptible to postharvest floral abscission caused by Botrytis cinerea infection. Pot- and field-grown waxflower cv. Mullering Brook plants and/or their harvested sprigs were spray treated with three known host plant defence elicitors, methyl jasmonate (MeJA), benzothiadiazole (BTH) or silicon (Si), and challenged with Botrytis cinerea after harvest. The efficacy of multiple MeJA, MeJA combined with BTH or Si and combined preand postharvest MeJA treatments in suppressing B. cinerea disease and floral abscission was assessed. Preharvest foliar applications of MeJA (1000 μM; two or four times), MeJA combined with BTH (150 mg/L) and MeJA combined with Si (1500 mg SiO2/L) generally did not suppress B. cinerea development and floral abscission from harvested sprigs. MeJA plus Si applied to pot-grown plants slightly and significantly (P<0.05) increased disease incidence and severity and flower fall. However, application of a MeJA postharvest (1000 μM) spray or pre- (1000 μM) plus postharvest (500 μM) MeJA sprays, significantly (P<0.05) reduced B. cinerea incidence and severity on sprigs from field-grown plants. Overall, the preharvest plus postharvest 1000 μMMeJA spray treatment consistently and significantly (P<0.05) suppressed B. cinerea infection on flowers from both pot- and field-grown plants. However, there was little or no impact of these treatments on floral abscission. Thus, multiple applications of chemical elicitors do not show promise as an approach to controlling B. cinerea-induced postharvest floral abscission in Geraldton waxflower.