48 Provincial Boaed of HoETicaLTUKE. 1897 



FUNGOUS DISEASES OF TREES, PLANTS, AND FRUITS. 



The following excerpt, re these, is taken from Bulletin No. 23 of the Central Experimental 

 Farm : — 



"A brief consideration of the principles underlying the practice of spraying may enable 

 the grower to understand the nature of fungous diseases, and this will be of service in directing 

 an intelligent application of the remedies which are recommended. A glance at the character 

 and habits of parasitic fungi will throw light upon the system of treatment. 



The wotA fungi is used to designate an exceedingly numerous class of plants of simple 



organization; we must never lose sight of the fact that they belong to the vegetable world, 



and are therefore subject to the ordinary conditions of plant life. Some of 



INature ot them derive their nourishment from living plants or animals, others from 

 dead plants or animals. Those which draw their food from other plants 

 more highly organized than themselves are termed parasites, and it is with this class that the 

 fruit-grower, is chiefly concerned. These plants (parasitic fungi) have not the power of assimi- 

 lating food from the soil or atmosphere, and therefore must obtain it in a prepared condition 

 through the agency of the higher plants upon which they feed. The vegetative part of a 

 fungus — that part corresponding to the root, stem and leaves of the higher plants — is made up 

 of delicate thread-like tubes, usually more or less matted together; these collectively are 

 termed mycelium. The term hypha is applied to a single thread-like tube. Parasitic fungi 

 bear no seeds or flowers, but are reproduced by spores, which are borne upon specialized 

 branches of the hyphas. These spores are produced in great numbers and are the principal, 

 though not the only, means of spreading disease. The hyphie-threads of the parasitic fungi 

 penetrate the tissues of the host plant — a name applied to the plant upon which they feed. 



The spores are exceedingly light and easily carried by currents of air. "When one falls 



upon a leaf and is supplied with moisture it germinates by sending out a slender tube, which 



. effects an entrance into the tissues of the leaf through the breathing pores 



of'Flj"ngi°" (stomata) or intercellular spaces. After the parasitic fungus has thus 

 entered the iriterior of a leaf, it develops rapidly at the expense of the 

 tissues of the latter. Pushing forward from one cell to another, the contents are appro- 

 priated and fresh vigor is thus gained by the parasite. This goes on till the vigor of 

 the host plant is much impaired, or its life destroyed. Some of the principal parasitic 

 diseases attack both foliage and the fruit of the host plant, as in the case of the " mil- 

 dew" of the grape, "scab" of the apple and pear, and " rot" of the plum and peach. They 

 are thus doubly destructive. If this destruction were confined to a few cells, leaves, or even 

 to a few plants, the loss would be trifling; but the extraordinary rapidity with which fun^i 

 multiply, and the ease with which their reproductive bodies (spores) are carried from plant to 

 plant, renders their extirpation a very difficult matter. 



.u ^^^''t ®JP1*"^*'°i of *he methods of reproduction and growth of these diseases emphasizes 

 the truth of the maxim that "prevention is better than cure." When the mycelium of the 

 tungus has become established within the tissues of the host plant, any remedy applied to the 

 exterior of the plant, it is readily seen, can at the best be only partially effective 



Fungous diseases, in accordance with natural laws, will in all probability increase in 

 number, in proportion as the food plants upon which they prey are multiplied, and as climatic 

 conditions are favourable to their development." 



i here are many ways in which the injuries of fungous diseases may be prevented. Among 

 these are the following : — j c a 



vuJhKt^ "" ^^""T^ r^\^^°^ ^°':^T '^'^''°"* important exceptions, plants weakened in 

 vitality are more subject to the attack of parasitic fungi than those in vigorous growth. Con- 

 Fertilisation and '"'"'i"/' njethods of cultivation and fertilisation, which tend to produce 

 Cultivation. ^"acticabT^ '^'^ ^^^^^ niaturity, should be adopted as far as 



