FIGHTING FINGER AND TOE.

Otago Witness, Issue 3495, 8 March 1921, Page 8

FIGHTING FINGER AND TOE.

Somewhere some time during the sea-son we learn of some pest or other affecting the ro P t crops. The wonder is why such faith is put in turnips to tide over the months of scarcity of stock food. It is becoming more difficult apparently each year to raise a crop free of disease. It is early in the season, yet we hear of ! club-root among turnips. This disorder, , known as club-root, or finger and toe, in ] turnips, cabbages, cauliflowers, rape, and I °ther cruciferous crops is the name given to a malformation of the roots. When 1 pulled, the main rctfi is found to be much ; dwarfed,. whilst the side noots are often swollen into spindle-shaped masses, pre- ! Benting an appearance to "which the name of finger and toe is appropriately applied. Lumps or nodules may also be seen up-on the root. A crop thus affected ultimately perishes, owing to the decay of the roots. This disorder, by whatever name—clubroot, finger and toe, or anbury—it may be called, must not be confused with a malformation of the root which occasionally arises as a result of some peculiarity of the soil, seed, or manure, and is really a case of ‘‘reversion” to the wild type. In such instances the growths, though distorted, are nevertheless healthy, but, when the fungus is present, it is only necessary to cut across the root in order to see that it is filled with decaying matter. The disease club-root in turnips is associated with the presence of a slimy fungus, known as Plasmodiophora brassiere. The spores of this organism are exceedingly minute, and they not only attack and destroy cruciferous plants, but they infest the soil to so great an extent that it is unwise to grow such crops upon the same land again for several years. | A spore, existing in the soil, finds, its way i into a cruciferous plant through a root . hair, and at once makes a demand upon | the photo-plasm of the plant. The spores produce slimy masses called plasmodia, ; and these have a slight power of locomotion from cell to cell of the infested plant. ; The refuse of a diseased crop should not ; be left in the field nor thrown upon the | dung-heap, for in either case it is capable of jerving as a new source of infection. | At- Cockle Park excellent results have - been achieved by dressing the affected I land with two tons of ground lime per ; acre at the time of sowing, or preferably ! some time before the swedes are sown, ; and mixing the surface soil well with the ! lime. If possible, crops like potatoes or some crop which requires a good deal of working, should be grown between the application of the ground lime and the sowing of a swede crop. Dressing the land with lime has the effect of destrovj ing the spores of the disease in the soil. The disorder seemes to be more harmful on poor, thin, clay soils than on light, sandy soil. As the spores will remain alive in the soil if not disturbed for a considerable time —some years —control is not so simple in practice as in theory. Stock will spread the disease on their feet and poasiblv in their droppings, while acid soils are all in their favour, thus suggesting liming, the results of which may not, unless the treatment is heavy, be very apparent for some years. The fact that a sour soil is more subject to the disorder when growing cruciferous crops would suggest the avoidance of an acid manure like superphosphate, and the use rather of basic phosphate or slag. In the event of stocking an affected paddock, it would be as well to feed off as soon as possible. Neither the ground nor the run off from the crop should be used for turnip or rape growing for a period of seasons. Liming and the sowing of a totally different crop and the laying down in grass for a few years will in all probability "out” the disease. Club-root is more prevalent in the North Island than in the South, where, indeed, it is comparatively rare, although not uncommon in garden soils. It should be noticed, however, that contamination of soil over large areas from relatively email centres of infection might easily take place. Stock feeding on diseased crops might very readily carry away large numbers of spores on their feet when driven to fresh pastures. So it would appear good practice to limit as much as possible the movement of stock to paddocks which may shortly be put- down in roots. Liming and the sowing of any crop not related to root crops may safely be recommended, while some contend that leguminous crops should be grown on affected ground. Certainly a generous use of clovers in a mixture have proved beneficial on affected land. If it is not practicable to use the ground, burnt lime, then a heavy dressing of the carbonate is imperative. As much as seven tons per acre have been advocated in bad cases, and preferably in the autumn. It cannot, we think, be with reason contended that certain swede varieties are immune

from club-root, although doubtless there are some varieties which are more resistant to attack than others.