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Press, 5 August 1988, Page 10

GARDENING

by

Mike Lusty

Please find enclosed samples of parsnip which have some disease. About half the crop is affected, and I would like to know the reason for it aand if there is any cure?—“Parsnip” (Chch). ■ Parsnip canker, also referred to as rust, is a problem wherever parsnips are grown. Weather conditions are a factor which influence incidence of the disease, and it is likely to be most severe in alternat-

ing wet and frosty spells, especially where the crop is growing in heavy, less freedraining soils. Sound cultural practice will help to alleviate the problem. Good drainage, adequate lime and potash levels in the soil, the application of a copper-based, material, or zineb, to the foliage at intervals and the avoidance of too early sowing in the spring time particularly in heavier ground can all help towards achieving better results.

Could you please identify what is wrong with the enclosed rubber plant leaf. Successive leaves, starting from the lower ones, show this scarring which gradually spreads across them.— P.K. (Lyttelton). It is possible that the problem is a disease brought on by faulty cultural attention. Points to observe with these plants over the winter months are to avoid placing near any form of heating, keeping the plant in a dry atmosphere and excessive over or underwatering. Problems can also arise if the rubber plant is kept on a window sill close to the glass.

Could you tell me the treatment necessary for a Black Hamburgh grape variety? It is only a young one, but was badly infected with mildew and heaven knows what else. What with, and when, should it be sprayed?—B.W. (Chch). Black hamburgh is a variety which is rather notorious for its susceptibility to fungal infections. A thorough application of lime sulphur is suggested on completion of pruning, with a follow-up of wettable sulphur at bud movement and again before flowering. Other fungicides could be substituted, particularly later in the seasons, for the control of powdeiy mildew as well as such diseases as botrytis. It should be noted that this variety of grape is possibly more suited to glasshouse culture in our climate.

My daphne bush wants to grow but continues to be