Tree mulches reduce sclerotial numbers and apothecial production by Ciborinia camelliae

Abstract

Mulches made from leaf and wood materials of pine (Pinus radiata), gum (Eucalyptus leucoxylon), kanuka (Kunzea ericoides), and a commercial mix containing numerous tree species, were evaluated for their ability to reduce viability of sclerotia and to suppress apothecial production in Ciborinia camelliae. The mulches were applied 100 mm thick to soil beneath camellia (Camellia spp.) bushes in late summer, allowing time for the treatments to act on the population of over‐wintering sclerotia. In the following spring, the mulches completely suppressed apothecial production by existing sclerotia, compared with the untreated control, which had 90 apothecia/m2. By early summer, the mean numbers of viable dormant sclerotia were reduced from 294/m2 in the untreated control to 147, 95, 75, and 47/m2 for the commercial mix, kanuka, pine, and gum mulches, respectively. In in vitro trials, mycelial growth from C. camelliae sclerotia placed on potato dextrose agar amended with mulch leachates (50:50 v/v) differed between leaching periods and mulch types. With the 1‐day leachates, growth was almost totally inhibited by the commercial‐mix leachate, but enhanced by gum and kanuka leachates compared with growth on control plates. Similar results were obtained for 20‐day leachates, except that mycelial growth was suppressed with the commercial‐mix and pine leachates. Thus, tree mulches offer potential for reducing the incidence of camellia blight by suppressing apothecial production and enhancing sclerotial degradation.