Gardeners’ queries

Press, 29 August 1980, Page 5

Gardeners’ queries

Could you identify for me.' from the enclosed cuttings, the disease which has attacked my young hibiscus? Are the peculiar, black, seed-like pieces under the bark normal, or Is this part of the cause of the die-back of the little tree? The plant was covered, in bloom in the late spring. Not having grown an hibiscus before I thought the withered and dead leaves were normal till I pruned it back to live wood. "Concerned'' (Ross). Your hibiscus is unfortunately suffering from an incurable tlisease known as sclerotinia. This fungal disease is typified by the development

of-small, hard, black fruiting bodies, called sclerotia, which, lie embedded in the stem of badly infected plants. Wet soil conditions and high humidity favour the disease, which cannot be controlled once infection has entered the host. The best thing to do in such cases is to carefully pull up the plant and burn it. Sclerotia remains viable in the soil for at least two years, and it is therefore advisable to sterilise the area before replanting anything in it. Suitable sterilants include formalin, applied as a 1:50 drench, and the incorporation of dazomet granules in the soil. ,