80 



service berry aud liawtliuru are frequently diseaseil, but not to such nu extent 

 as the first-uauietl trees. There is a difference in tlie susceptibility of varieties. 

 Thus, among pears. Clapp"s Favourite. Flemish Beauty, and Bartlett are more 

 liable to the disease than Keiffer and Duchess, and amongst apples, the t'rab 

 varieties are the least resistaut. 



Climatic couditious influence the disease; warm, moist weather with 

 much raiu favour it, whilst bright, dry, sunuy weather tends to check it. 



High cultivation, rich soil, heavy manuring, free use of fertilisers, heavy 

 pruning, or any other treatment which has a tendency to induce uew and 

 succulent growth, favours the disease, as the bacteria grow with far greater 

 rapidity and penetrate more ijuiclily from cell to cell when the tissues are 

 gorged with sap. Insects are more partial to young succulent shoots and 

 leaves, and the bites and iniuctures of such insects whose mouth parts may bi' 

 contaminated with pear blight germs often serve to infect the tree. 



It is thus manifest that healthy, thrift.v. vigorous, well fed and well 

 cultivated trees arc more Vahle to Die disease than others, and hence the 

 severity of an attack of Are blight may be les.sened by couditious which are 

 under the control of the grower. 



Treat iiicnt. 



The treatment of fire blight is of two kinds — that which is designed to 

 put the tree in a condition to withstand the attack of the blight microbe, and 

 these methods which aim at the extermination of the casual bacterium. 

 Vnfortunately, all methods which are used for hindering the attack of the 

 microbe consist of restraining tlie full development of the tree, and hence any 

 such system of procedure should not be followed unless an orchard is very 

 badly atacked. 



High cultivation, with pruning and the other conditions already mentioned 

 as predisposing trees to blight, should be avoided, but the trees should be 

 allowed to ripen the wood, and in order to do this the fruit-grower must use 

 any method which will check the amount of moisture in the soil — for instance, 

 b.v the growth of a clover crop. 



The fire blight organism caunot be exterminated by spra.ving. as the 

 microbe lives in the tissues beneath the outer bark, and it is impossible to 

 reach it with any spraying solution, for, unless the bacteria come :nto contact 

 with the germicide, spraying is ineffectual. 



There is. therefore, but one remed.v, to cut out and Inirn the affected 

 parts of the tree. It is very necessary when cutting out a diseased brandi 

 or twig tn cut well below the discoloured portion, as the bacteria are in most 

 cases far lielow the discoloured portion, the discolouration uot being produced 

 immediatel.v upon the appearance of a few bacteria, so that if onl.v the dis- 

 coloured portion were cut off numbers of bacteria would still be left in the 

 stump, and these would continue to nuiltipl.v. and the disease would soon be 

 evident again. 



Cutting of affected parts ma.v be done at any time in the winter and 

 spring, but it is not advisal)le to cut in the growiug season, as fresh cases may 

 be constantl.v occurriug, and these, owing to lack of suflicient development. 

 would uot be seen. 



