, Volume 20, Issue 2, pp 67-72

Phoma clematidina, causal agent of leafspot and wilt of Clematis in New Zealand

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Abstract

Phoma clematidina (Thüm.) Boerema is shown to be the causal agent of leafspot and wilt of large-flowered Clematis L. hybrids, and leafspot of clematis species. P. clematidina is a wound pathogen and causes leafspots on both wilt susceptible and wilt resistant cultivars. Wilting is usually the result of nodal rotting or ‘stem girdling’ following hyphal extension into the node from the infected leaf. Resistance to wilt is manifested by abscission or senescence of infected leaves. The fungicides chlorothalonil and fenpropimorph were the most effective of those tested for inhibiting spore germination and mycelial growth, respectively. A mixture of these fungicides significantly reduced the number of leaf lesions after wound inoculation. Other fungicides, including dichlofluanid, captafol, prochloraz and propiconazole, also displayed in vitro fungicidal activity and could be useful alternative sprays for chemical control, although proper plant hygiene and maintenance are important for disease-free clematis.