Aetiology and biological control of Fusarium wilt of pinks (Dianthus caryophyllus) using Trichoderma aureoviride

Fusarium oxysporum f.sp. dianthi (F.o.d.) was the species isolated most frequently from wilted glasshouse-grown pinks in south-west England, whereas F. avenaceum was less prevalent and F. culmorum was not found. Although infections by F. avenaceum, via the roots or through a cut-stem wound, caused symptoms identical to those characterizing mild infections due to F.o.d., the former was always pathogenically weak relative to the latter. Of several organisms screened for potential antagonistic capacity towards F.o.d., using an in-vitro dual culture plate technique, Trichoderma aureoviride, isolated as an endophyte from healthy pinks, proved most effective. Elevated temperatures substantially reduced the antagonistic capacity of micro-organisms in both in-vitro and in-vivo screens, except in the case of T. aureoviride where maximum antagonism occurred at 28°C, which was near the optimum for wilt disease in pinks. The tolerance shown by T. aureoviride to a wide range of pesticides used in commercial production of pinks under cover indicated its potential in a proposed integrated disease control programme.