DISEASE IN TURNIPS

New Zealand Herald, Volume LXXIII, Issue 22431, 29 May 1936, Page 5

DISEASE IN TURNIPS

CONTROL OF BROWN HEART

SERIOUS LOSS PREVENTED

SUCCESSFUL BORON TREATMENT

BY W. ALEXANDER

Brown or mottled heart in swedes lias been responsible for serious losses, both in the yield and in feeding valuo of crops in various parts of New Zealand, llie disease is widespread in its incidence and occurs on almost all soil types. As far as we know no variety of swede is immune. Reports from other parts of the world indicate general concern at the widespread incidence of this disease and the alarming crop losses experienced. Research workers have been investigating the position, particularly in connection with the growing of sugar beet—a crop also susceptible to damage by brownhem t and as a result of their efforts we are now in a position to effect complete control. Disease Symptoms Brown-heart usually makes its appearance in the second half of the vegetative period and is seldom noticeable in very small-sized roots. There are no outward signs of the disease, both the leaves and the skin of the bulb presenting a normal appearance. It is this capacity of the swede to grow to an apparently normal size and condition that is misleading. It is only when the bulb is actually cut that the injury caused by brown-lieart is disclosed, llien it is seen that the inside portion of the flesh is discoloured and has taken on the appearance of a piece of petrified wood. The diseased tissue is located principally in the lower portion of the bulb and may escape notice altogether if a cut is made across the top. As the bulb reaches maturity the area affected by brown-heart seems to increase in proportion until little more than a rind is left sound. The tissues harden and shrink until a very dry and unpalatable condition remains. Not only is yield lowered, but feeding value is seriously impaired. Attempts at Control

Various attempts to control this disease in New Zealand soils met with no success until the present. Peaty lands appeared to be the worst offenders, and the prevailing idea here was that the swedes absorbed some element from the peat that caused this hardening and discolouration of the centre. Lime in heavy dressings was tried, potash was added to the phosphates used as fertiliser, but always brownheart developed. Later it was found that swedes grown on pumice soils also developed the rliseaso, but still no control measures were forthcoming. It was not until reports of experiments with the mineral boron tried out in the sugar-beet areas of England were received that the writer saw a chance of saving the swede crops of New Zealand from destruction by brown-heart. Successful Experiments

Early last spring the Lands and Survey Departmental officers responsible for the development work at Galatea referred to the writer the question of a suitable fertiliser for swedes on that light pumice country. Brown-heart had already appeared in previous crops with a resultant loss in feeding value and this fact was taken into consideration. A special fertiliser mixture, approximating a standard turnip mixture, was prepared for the whole swede crpp. In order that the effect of boron on Galatea soils could be studied certain small areas on the swede land were set aside to receive a small quantity of boron an acre, in addition to the fertiliser mixture. This boron w 7 as added during the preparation of the fertiliser mixture to ensure the small quantity used was thoroughly mixed with the larger quantity of mixture. The seed and manure were drilled in the ordinary way. The swede crop over the whole area germinated very well and grew normally. There were several areas in swfedes, the crop being distributed on various parts of the station. The boron treated strips occured on. some three or four separate areas. Field Examination

A fortnight ago the writer, accompanied by the Galatea Development Committee and several farmer visitors, made a close examination of the boron trials. The story can be told in a few words: Outside the boron-treated strips it was hard to find a swede that was free from brown-heart; inside the borontreated strip we did not find one affected with brown-heart. Complete control had been secured in one season by the addition of a few pounds per acre of boron to the turnip fertiliser. Representative plots were selected and the roots growing thereon were pulled and weighed. It was found that where the boron had been used there was an increased yield to the extent of five to eight tons an acre. The increased yield alone would pay for the amount of boron used many times over, but even that advantage is small compared with the fact that where the boron was used the crop was absolutely sound and free from brown-heart and of excellent feeding value. On the other hand, the crop without it was damaged and reduced to a winter fodder of low feed value. On light pumice country the difference between a heavy concentration of stock and a light one, consequent upon a good or a poor crop of swedes, makes all the difference to the subsequent establishment of pasture, so that it is not too much to say that the use of boron is destined to' influence the whole farm rotation. Perhaps the most significant feature is the fact that the boron treatment costs only 2s to 3s an acre.