498 the farmers' handbook. 



Control. 



(1) The Use of light-free Seed. — As the mycelium (the vegetative portion 

 of the fungus may be dormant in the tuber, and often shows no outward 

 signs of its presence, no seed should on any account be used from a crop 

 that is known to have been diseased. Seed should be obtained from a place 

 known to have been free from blight for some years. Any seed showing 

 traces of Brown Eust should be picked out and destroyed by boiling 

 or burning. Often the grower saves his own seed, after sending the best to 

 market. It would pay him to keep the best for his own sowing, remember- 

 ing that " the best is never too good." 



(2) Clean Land. — If the previous crop was potatoes which were blighted, 

 the infected field should be carefully cleaned. Parts of the plants, small or 

 rotten potatoes left in the ground, and the soil are all dangerous, owing to 

 contamination with the fungus and its spores. All remains should be care- 

 fully collected and burnt on the spot. The practice of ploughing in potato 

 haulms is liable to produce greater loss through disease than any increase 

 in yield from the manurial value. It must be remembered also that infec- 

 tion may be carried to other parts by the implements of the workmen. 

 Where it can be arranged it is very advantageous to grow some other crop 

 for the next season or two. 



(3) Spraying. — There is now abundant proof that spraying has proved 

 an almost complete remedy for Late Blight. It will not do to wait until 

 plants show signs of disease. Spraying should commence early, and every care 

 should be taken thoroughly to spray both the lower and upper surfaces of 

 the leaves as well as the stems and the soil. It has been proved that 

 spraying the soil prevents tuber infection by the spores that are washed 

 down through the soil. Spraying must be repeated often enough to keep the 

 whole plant covered with the fungicide, and to protect newly-formed foliage. 

 It is not to be looked upon as a cure for blight, as once a plant is attacked it 

 is hopeless, and should be dug out and burnt Several sprayings should be 

 given in February and March to protect the plants from infection induced 

 by the active growth of blight owing to the summer rains. Either Bordeaux 

 mixture, or where good lime is not procurable, Burgundy mixture is 

 recommended for the spray. 



Bordeaux Mixture. 



The formula recommended by the Department for use in connection with 

 potatoes is as follows : — 



Copper Sulphate (Bluestone) ... ... 6 lb. 



Freshly-burnt Lime ... ... ... 4 lb. 



Water ... ... ... ... ... 50 gallons. 



Two or three fairly large wooden vessels are required to make the mixture. 

 If, for instance, it is intended to make 50 gallons of spray, two tubs or 

 barrels capable of holding 25 to 30 gallons of water are needed and one of 

 a capacity of 60 gallons. 



For the copper solution, wooden vessels are preferable, though copper ones 

 may l»e used. Iron should be avoided. For the lime, use wooden tubs or 

 barrels. 



