ISHS Acta Horticulturae 156: XII Working Party on Greenhouse Cucumbers
BLACK ROOT ROT CAUSED BY PHOMOPSIS SCLEROTIOIDES VAN KEST. - THE MOST DESTRUCTIVE DISEASE OF GLASSHOUSE CUCUMBERS NEW TO POLAND |
| Author: | B. Leski |
| Abstract:
P. sclerotioides, not previously reported in Poland, were found in every of the above 350 cucumber crops under cover observed since 1972, and in a majority of them at a harmful level. Other diseases occurred mostly locally. The isolation of P. sclerotioides was greatly improved by inhibiting the lower fungi in media amended with selective fungicides emgm ethazole or metalaxyl /150–200 mg/1/. A great majority of the above 300 isolates of the pathogen were highly pathogenic to cucumber. The fungus pycnidia, both with alpha and beta spores, were observed in the cultures. P. sclerotioides were consistently found /and isolated/ on cucumber roots planted for the first time in fresh soil or substrate in new glasshouses, although often in a just barely detectable amount. It was also occasionally isolated from cucumbers experimentally seeded in fields never cropped with cucumbers, or in virgin forest soil. P. sclerotioides occurred to be pathogenic to various plants although black lesions similar to that on cucumber have been found only on alfalfa and red clover. Several Phomopsis - like isolates from alfalfa, soybean and china aster were pathogenic to cucumber with root symptoms typical to P. sclerotioides. The effects of growing systems combined with fungicide treatments have been tried in commercial crop conditions. Treating the ground soil with thiram /5–7.5 g/m2/ with /or carbendazim /2–4 g/m2/ before "macking up" the beds of fresh substrate and spraying the fungicides over beds at intervals prevented the substrates from quick reinfestation by the pathogen. | |
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