CONFEKENCE ON FRUIT GROWING . 



35 



various mildews, being wholly superficial, can be held in check by spraying 

 if applied sufficiently early. 



In all instances it must be remembered that spraying acts only as 

 a preventive. It never cures. The one object of spraying is to deposit 

 some substance on the leaves that kills all fungus spores alighting thereon. 

 By such means an epidemic or serious outbreak of disease can be 

 prevented. In theory every portion of the foliage, both surfaces and 

 young shoots, are supposed to be coated with the substance used. In 

 practice the theoretical idea does not work out. If the spray is rather 

 coarse, the liquid runs into drops and trickles off the surface of a polished 

 leaf. If the leaf is covered with matted down or hair, the solution cannot 

 displace the entangled air, and the surface of the leaf remains dry. If 

 the spray could be made to resemble a London fog it would wet every 

 portion of a plant, and the plants need not be directly sprayed at ; but 

 no machine at present in existence will give this ideal condition of things, 

 at least not out of doors. In the end we are compelled to return to the 

 old but nevertheless certain method of preventing an epidemic : that is, 

 cleanliness. Where good cultivation is practised, where every symptom 

 of disease is nipped in the bud, and where all diseased material is 

 promptly removed and destroyed, epidemics of fungus disease do not 

 prevail. 



A little time devoted to the broad features of fungi as a group of 

 plants would repay the cultivator. When an acorn is planted, the first 

 product is an oak tree in miniature. With many of our most injurious 

 fungi this is not so ; the parasite first appears on a given kind of plant 

 under a particular form. The spores produced by this form are carried 

 by wind or insects to a different kind of plant, where the fungus com- 

 pletes its growth under a form totally different from that of its first 

 condition. The knowledge that these two forms are conditions of the 

 same fungus is very important from an economic point of view. 



Fungi are very abundant on the leaves of nursery stock, where they 

 form reddish patches or minute holes that cause the leaves to fall early 

 in the season. At any one given time such an ^attack appears to be a 

 trivial matter, but if this happens two or three years in succession, as it 

 certainly will if not promptly attended to, the wood is not matured, 

 grafting becomes a difficult matter, and the injury sustained is never 

 eliminated. 



Of late years much has been attempted, and a little accomplished, in 

 the matter of producing races of plants immune to their most dangerous 

 fungus pest. Probably greater success awaits investigation in this 

 direction. One point in this connection appears to have generally been 

 overlooked ; that is the fact that fungi are very elastic in their mode of 

 life, and are ever ready to adapt themselves to circumstances ; in fact we 

 have evidence that something of the kind is already at work. It is a well- 

 known fact that a plant immune against a given fungus in one district 

 often falls a prey to the same kind of fungus when removed to a new 

 district. 



Mr. Bunyard : What about the silver leaf ? 



Mr. Massee : I know absolutely nothing about the silver leaf. I have 

 tried for years and years to find a remedy, but I have not succeeded. 



D 2 



