I. Dori, I. Ganot, D. Shmuel, E. Matan, Y. Messika

Grey mould, caused by the fungus Botrytis cinerea, severely affects lisianthus. The fungus
infects the stem bases of whole plants, and plant stubs that are left after flower harvesting.
Dense canopy and leaf rosettes close to the ground prevent adequate air movement and proper
disease control. Chemical fungicides frequently fail to control the disease. In the present study,
isolates of B. cinerea recovered from diseased lisianthus plants in greenhouses were tested for
resistance to benomyl, fenhexamid, fludioxonyl, iprodione and pyrimethanil. Isolates resistant
to dicarboximide and benzimidazole fungicides were widespread and comprised 65 and 27%,
respectively, of the isolates tested. Eleven per cent of the isolates were resistant to
pyrimethanil, and a few (3%) isolates showed resistance to fenhexamid. No isolates resistant to
fludioxonil were found. Isolates resistant to several fungicides comprised 32% of resistant
isolates, and 24% of the tested isolates were sensitive to all the fungicides. Therefore, we
studied integrated management of the disease. Six different chemical fungicides, applied
before infection with B. cinerea, suppressed disease under controlled conditions. Only
pyrimethanil, fenhexamide and iprodione effectively suppressed grey mould when sprayed
after infection with a sensitive B. cinerea isolate. Microclimate management by covering the
greenhouse soil with polyethylene, burying the drip irrigation system, reducing plant density,
increased calcium fertilizations, and chemical fungicides were examined under commercial
conditions. Polyethylene soil cover and buried drip irrigation significantly decrease the
humidity in the greenhouse and suppressed grey mould on the stem base or plant stubs.
Decreased planting density reduced disease levels significantly. The tested fungicides
fenhexamid and pyrimethanil, or their alternation with iprodione applied by spraying, were
effective, and reduced disease incidence under conditions less favourable for the pathogen,
which were achieved by cultural control. An integrated control system for grey mould was
developed based on the above results.

Persistent Identifier: urn:nbn:de:0294-sp-2008-Reinh-4