436 



INJURIOUS INSECTS AND FUNGI. 



[March 189G. 



in a few hours in a temperature of 65° Fahr., in the manner 

 shown at B. As noticed before, the mycelium does not enter 

 the leaf but merely spreads over it and chokes the stomata,. 

 preventing the absorption and exhalation of gases and the 

 exhalation of watery vapours. An unhealthy state conse- 

 quently occurs, and the plant-growth is seriously affected. 



Methods of Prevent ion and Remedies. 



Good tillage, a good season, to start with, and plenty of 

 lK)rse-hoeing prevent mildew. Well-manured plants are not sO' 

 liable to mildew as those which are starved and unable to grow 

 in droughty weather. 



This fungus is found upon charlock and other cruciferous 

 weeds, as well as on some of the spiraeas, notably Spircea 

 idmaria (meadow sweet), and upon burnet and other weeds. 

 Charlock should be kept down as harbouring many insects and 

 fungi injurious to crops. 



When swedes are infected and apparently standing still, 2 cwts. 

 of guano or 1^ cwt. of nitrate of soda would help them 

 materially. 



In attacks of this fungus the plants should be sprayed with 

 houillie hordelaise of a strength of 12 to 15 lbs. of pure sulphate 

 of copper and the same quantity of lime to 100 gallons of water,, 

 put on with a horse potato sprayer arranged so as to spray the 

 upper and under surfaces of the leaves. 



This spraying with sulphate of copper and lime destroys the 

 fungus and gives relief to the plants. 



For cucumbers and vegetable marrows, a houillie hordelaise of 

 10 lbs. of sulphate of copper and 10 lbs. of lime to 100 gallons 

 of water should be used, applied by means of a knapsack 

 machine, directed under and upon the leaves. 



This spraying must be carefully done, or it may affect the 

 delicate blossoms of cucumbers and marrows, and these must 

 ' not be sprayed when the fruit is approaching to ripeness. 



In houses or frames, cucumbers and marrows may be treated; 

 with powdered sulphur, put on with a soufflet (figured below).. 

 The heat of the houses and frames causes considerable volatilisa- 

 tion of the sulphur, forming sulphurous acid gas, which destroys 

 the fungus. 



Fig. 2. 



