CONTROL OF CLUB-ROOT IN CABBAGE SEED-BEDS.

New Zealand Journal of Agriculture, Volume 50, Issue 5, 20 May 1935, Page 294

CONTROL OF CLUB-ROOT IN CABBAGE SEED-BEDS.

J. G. Gibbs,

Mycological Laboratory, Plant Research Station, Palmerston North.

Club - root is a disease . which attacks cabbage, cauliflower, brussels sprouts, and allied crops. It produces a tumid distortion of the roots, and often causes wilting and premature death of the plants. Infection is caused by. spores in. the soil. To obtain healthy seedlings, .which are essential .to the production of healthy crops, the spores may be eradicated from infected seed-beds by soil disinfection. Commercial growers possessing high-pressure boilers will find steam disinfection. the most economical method ; but where steam is not available a chemical disinfectant must be used. At the Plant Research Station, Palmerston North, three seasons’ experiments on heavily infected ground* have shown that a o-i per cent, acidulated solution of mercuric chloride is the only economically efficient disinfectant for the eradication of club-root, from the soil. The treatment costs approximately qd. per square yardf, and must be applied before sowing. It has no detrimental effect on subsequent germination or growth. Mercuric chloride solutions are strong poisons and rapidly corrode metals. They should he kept out of reach of children and stock, and containers should be washed after 'use. As corrosion weakens the disinfectant, the tins and watering-cans used during application should be protected by rinsing every two hours with benzine containing a little oil.

Method of Application.

A concentrated solution of the disinfectant which may be kept bottled indefinitely is made up as follows: Mercuric chloride (powder), i lb.; commercial concentrated hydrochloric acid, .3 lb. The seed-bed should be prepared for sowing and divided into areas of 2 square yards. Water in 4-gallon tins is carried to the bed, and there if fluid ounces of the concentrated solution rapidly stirred in. The disinfectant solution so formed should be distributed immediately through a fine rose evenly over the 2 square yards previously marked out. Penetration of the disinfectant is deeper when the surface soil is moist and when a gallon of clean water per square yard is applied about an hour after treatment. The seed-bed should be left for ten days before sowing. The efficiency of the method depends ' on (i) the rapidity with which the mercuric chloride solution can be poured on the soil, and (ii) the prevention of reinfection by disease-carrying soil. Implements and boots should be disinfected in a solution of mercuric chloride immediately before working on treated beds : for doing this a wooden bucket containing f fluid ounce of the concentrated solution per gallon of water, placed near the seed-beds, is helpful. For satisfactory disinfection it is advisable to wash adhering earth from the implements, &c., and to keep them damp with the disinfectant for ten minutes. Metal implements should not be left immersed in the mercuric chloride solution for more than a few seconds.

% * Full details of these experiments were published in the Journal of Sci. and Tech., Vol. 14, pp. 145-51, 1932, and Vol. 16, pp. 159-62, 1934. - f This price is calculated with the retail price of mercuric chloride at 15s. per pound, but by co-operative buying the price of treatment should bereduced to less than 2fd. per square yard.