Attempts to control Botrytis cinerea on roses by pre- and postharvest treatments with biological and chemical agents

Abstract

The biocontrol agent Trichoderma harzianum and the fungicides polyoxine B, fenpiclonil, tebuconazole with or without dichlofluanid, and fenbuconazole were sprayed once a week in a rose greenhouse. Botrytis infection of branches was reduced by 50–70%. The importance of reduction of conidial inoculum by this treatment is discussed. Severity, but not incidence, of petal infection was found to be controlled significantly by some of the fungicides only 2 days after the application and not 5 days later. Fenpiclonil, tebuconazole, dichlofluanid alone or alternated with T. harzianum, and T. harzianum also reduced development of grey mould on flowers that were harvested soon after the treatment and incubated under Botrytis-conducive conditions. This beneficial effect was observed only with latent natural infection and not in flowers inoculated with B. cinerea conidia after harvest. The difficulty of controlling the disease by sprays in the greenhouse is discussed. Postharvest treatments by spraying cut flowers with the fungicides iprodione plus thiram, tebuconazole plus dichlofluanid and polyoxin D, but not with another 11 treatments, reduced disease incidence significantly by 50–58%.