Insects and Fungi Attacking Trees, Etc. 325 



the last being composed of myriads of spores or seeds. 

 These spores are very small, so small in fact that they 

 are individually scarcely perceptible to ordinary vision and 

 are carried about by the slightest breath of air. 



Much may be done to prevent the growth of fungus 

 pests by keeping the trees or plants in a \igorous, healthy 

 growth. This may be done by good cultivation and an 

 abundance of plant-food, under which condition the grow- 

 ing spores are not so likely to gain a foothold in the tissues 

 of the host plant; but even with the most vigorous growth 

 we sometimes find that if the weather is unusually hot and 

 the atmosphere very moist the spores will gain a foothold 

 and we must have the fungicide on the surface of the plant 

 to prevent the growth of the spores should the plant not be 

 able to withstand their attack. 



Some seasons, and often for a series of years, our trees 

 escape injury from fungus pests, but we cannot hope to 

 escape always, and it is the part of wisdom to learn with 

 what pests w^e are threatened, what is the best remedy, and 

 how and when to apply such remedies as to most certainly 

 destroy each pest. Among the best fungicides are the 

 f olloA^ing : 



Copper Sulphate {Blue vitriol). — Copper has long been 

 known to be destructive to the spores of nearly all kinds of 

 moulds, mildews, rusts, etc., but not until within a few 

 years has it been largely used for the purpose of destroying 

 these growths on cultivated trees, plants, and farm crops. 

 The form in which it is most used is that of copper sulphate 

 or blue vitriol, in which the copper is united with sulphuric 

 acid and is in the form of blue crystals (blue stone). In this 

 form it is quickly soluble and very injurious to the growing 

 parts of plants unless used in a very dilute form; i part of 

 copper sulphate to 150 or 200 parts of water being as concen- 

 trated as it can be used without injury. In this form it is 



