24 



THE CUBA REVIEW. 



SOME TOBACCO SEED-BED TROUBLES. 



Chief of Department of Vegetable Pathology, Cuban Agricultural Experiment Station. 



All the experience of the tobacco growers in Cuba has failed to find a sure 

 remedy for the damping off (pudricion or gangrena hiimeda) which appears in 

 tobacco seed-beds in moist weather. In dry weather this disease makes no serious 

 trouble, but in moist weather it destroys the tobacco at a terrible rate. 



This department has been studying the pudricion and has obtained results which 

 justify us in recommending certain preventive and curative measures. We also 

 recommend arsenate of lead in place of Paris green for poisoning the various biting 

 insects which injure young tobacco. 



In_ the semilleros del monte (upland seed-beds in recently cleared forest land) 

 there is an abundance of humus in the surface soil from the accumulation of decay- 

 ing leaves, branches, etc., excellent conditions for growing tender plants. Sterilizing 

 the soil by burning kills injurious fungi in the soil and the ashes furnish a quickly 

 available fertilizer. 



The department favors the growing of posturas (young plants) close to the field 

 where they are to be planted, and only from carefully selected seed. 



The vega (tobacco field) soil lacks humus, so that it dries quickly, but this is 

 remedlied by adding decayed compost to the soil. Unfortunately, this contains the 

 fungi which causes the pudricion and even encourages its growth in moist weather. 

 Burning over the seed-beds is not usually practicable for lowland seed-beds, so that 

 it is necessary to find some other way of sterilizing the soil, and this brings us to the 

 methods of prevention. 



Prevention of Pudricion. 



Two principal methods for sterilizing soil by a solution of formalin and by hot 

 water or steam have been tried in the United States and other countries, and are said 

 to have given excellent results. 



The latter will soon be given a thorough test. The first method is here described : 



First Experiment. 



Five seed-beds were prepared using red soil and chemical fertilizer. The standard 

 treatment was 2 pints of strong formalin (40%) in 5,0 gallons of water and approxi- 

 mately I gallon of the solution was applied to i square foot of two seed-beds. Two 

 other beds were wet with the same amount of water, and the last bed received a 

 double strength formalin solution. All were covered and left to diry out for 8 days. 

 The beds were then worked lightly, sterilizing all instruments with formalin before 

 using, thus avoiding the introduction of unsterilized soil into sterilized beds. All the 

 beds were then sown with tobacco and vegetables and liberally watered. 



All the sowings grew well. Tobacco and vegetables grew more thriftily in the 

 beds treated with formalin than in the other beds, and better still in the beds treated 

 with double strength formalin solution, showing that the formalin sterilizing was 

 having a beneficial effect on the growth of the plants. 



SEEDLING TOBACCO PLANTS. 

 The bed on the left is untreated with sterilizer. The one on the right was sterilized with a 

 strong .solution of formalin. The plants in the bed not treated quickly succumbed to pudricion 

 and died. 



