38 PLANT DISEASES 



those cases where a disease has previously existed, as it 

 destroys resting-spores that may be concealed in crevices 

 of bark, brickwork, or on the ground under fruit trees. 



In spraying fruit trees, vines, etc., the trunk and branches 

 should be thoroughly drenched ; but it is all-important to 

 remember that the spraying should be done during the 

 winter, or at all events some time before the leaf-buds 

 begin to swell, otherwise the foliage would be completely 

 destroyed. 



This preparation should not under any circumstances 

 be applied to leaves or fruit. 



Permanganate of Potash Solution. — This is the well- 

 known liquid called ' Condy's Fluid.' However, the most 

 economical method is to buy the potassium permanganate 

 in the form of crystals, which dissolve quickly in water. 

 The solution should be pale rose colour, and has proved 

 of use in arresting the spread of various kinds of rust. For 

 instance, if the leaves of seedling hollyhocks attacked by 

 rust (Puccinia malvacearuiii) are sponged with this solution, 

 the disease is checked ; rusted carnations also benefit by 

 being sponged, or, if circumstances admit, submersed in 

 the solution. Potassium permanganate is too expensive 

 for use in spraying on a large scale ; besides, the solutions 

 previously mentioned are more effective. On the other 

 hand, it may be used in small gardens or for greenhouse 

 plants with advantage. 



Sulphur. — This is used as a dry powder, in the finely 

 precipitated condition known as ' flowers of sulphur,' and 

 has been in vogue for many years previous to the discovery 

 of liquid fungicides. It is most effective against the fungi 

 popularly called mildews, belonging to the Perisporiacene, 

 where the mycelium is entirely superficial, usually forming 



