A Cucumber Leaf Disease. 



169 



with many others) is most prevalent and spreads most in dull 

 weather, and that during days of bright sunshine it will diminish 

 or may almost entirely disappear. 



This points to the fact already insisted upon, that atmos- 

 pheric conditions are largely responsible for attacks of these 

 fungi, and that when such parasites are present a slightly dryer 

 and more buoyant atmosphere should be given so as to reduce 

 as much as possible the chances both of germination of the 

 fungus spores and fresh infection therefrom, though when once 

 the fungus obtains a firm footing amongst the plants patience 

 will be required before it can be eradicated. 



Besides dryness, there is another factor of importance in con- 

 nection with the fine weather which may also materially help to 

 keep the disease in check, viz., light. It is, unfortunately, imprac- 

 ticable to supply a substitute for sunlight. But, at any rate, every 

 effort should be made to imitate the fine weather conditions as 

 much as possible, and even in the height of summer fire heat 

 may be necessary if damp, dull weather prevail. These are 

 points which must be largely controlled by the discretion of the 

 cultivator, suggestions only can be given here. 



With regard to spraying with fungicides, many of these have 

 been tried, but without much success. This is owing, partly to the 

 difficulty of ensuring that the fungicide reaches all the infected 

 parts, and partly because the cucumber foliage as generally 

 grown is not hardy enough to withstand any but very weak 

 solutions. 



As a preventative, it would be advisable to spray with a very 

 weak solution of potassium sulphide (1 oz. to 3 gallons of water)- 

 This should certainly be done if the houses were infected the 

 previous season ; the spraying should commence as soon as 

 planting out has taken place, and care should be taken to spray 

 the under side of the foliage. 



In clearing out infected houses in the autumn, dead leaves and 

 other rubbish should be collected and burned. As the fungus 

 grows readily as a saprophyte in the soil, it would also be advis- 

 able to wheel out all the old soil, manure, &c. A dressing of 

 gas-lime should then be applied to the floor of the pits in order 

 to kill the spores and mycelium, which are sure to be abundantly 

 present. The wood work of the houses should also be thoroughly 



