The wood decay of kiwifruit and first control measures

A wood-decay of kiwifruit is widely spreading in 9-10 (see introduction) yearold Italian orchards, and similar forms have recently been noticed in France and Greece. The disease appears on the leaves as chlorotic spots which later become necrotic. Necrotic areas are regular in shape and enlarge conspicuously. Leaves finally wither and fall prematurely. Fruits show a reduced growth and do not reach full maturity, although no symptoms are visible. The wood of infected plants is affected by a degradation process which usually starts from pruning wounds. Sections of the wood show white rot areas usually preceded by discolored tissue of hard consistency. Mitosporic (hyphomycetes) fungi Phaoacremonium aleophilum, P. inflatipes, P. rubrigenum and Phaeomoniella chlamydospora are found in discolored tissues, whereas the basidiomycetous fungus Fomitiporia punctata is isolated from the white rot. Although the aetiology of the decay is not cleared yet, pathogenicity tests have successfully been carried out by artificially inoculating the above fungi into the trunk of 2 year-old 'Hayward' potted plants. Mitosporic fungi were able to produce discoloration six months after the inoculation, whereas F. punctata caused white rot in the woody tissue eighteen months after inoculation. No foliar symptoms could ever be observed. Many-years control by cutting infected vines below the rotted and discolored wood showed the ability of almost all renewed plants to reach a full production level 2-3 years after the treatment. © ISHS.