HUSBANDRY PRACTICES AND THE CONTROL OF PENICILLIUM CORYMBIFERUM ON CROCUS

Disfigurement of Crocus corms by dry brown lesions developing during storage is a major problem. On some farms one third of the crop has been rendered unsaleable by this condition. Penicillium corymbiferum was found to cause the disease, which increased in severity following mechanical damage to corms during harvesting and grading. Infection of corms harvested and graded without mechanical damage was found to be slight. For this crop te be suitable for large scale farm production lifting and grading must be mechanised hence some damage to the corms is inevitable.

Three possible methods of reducing infection in commercially harvested corms were investigated: changes in harvesting practice, changes in storage temperature and use of fungicidal dips.

Defoliating the plants up to six weeks before harvesting failed to control the disease. Disease severity was slightly reduced by delaying harvesting until late July or August. A period of storage at 30°C after lifting is known to reduce infection of Gladiolus spp by Penicillium gladioli but was ineffective against P.corymbiferum on Crocus. Dipping corms in benomyl, captafol, mancozeb or thiram solutions dit not control the disease.

None of the control methods were effective. Prevention of mechanical damage offers the most likely means of control but may be difficult to achieve commercially. Modifying lifting machinery to reduce corm damage and possibly growing the corms in nets to make lifting easier are potential solutions.

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