Ciborinia camelliae Kohn is the most destructive pest or disease problem of
camellias (Camellia spp.) The pathogen is related to common and widespread
plant pathogens in the genera Sclerotinia and Botrytinia (anamorph=Botryti
s). Sclerotia form in infected petals and remain dormant in plant debris un
til the next season. In early spring, apothecia are produced from the scler
otia and release windborne ascospores. Infection causes the petals to turn
brown and the flowers to fall prematurely. The disease has been identified
in Japan (1919), the United States (1938), New Zealand (1993), and parts of
Europe (1999). It has now spread over the lower North Island and upper Sou
th Island of New Zealand, with isolated outbreaks in Christchurch and Auckl
and. Control of this disease has proved difficult even though: (1) only cam
ellia flowers are infected, (2) there is no secondary infection, and (3) as
cospores are present for only 2-3 months each year. To date, fungicides hav
e given less than satisfactory control of the disease and possible control
measures are reviewed. Interest in potential biocontrol agents is growing b
ut remains an unexplored alternative. Resistant varieties offer the best ma
nagement option for the future.