4 Introduction. 



trees are unhealthy. Fruit trees are grown under most unnatural 

 conditions, they are being forced to do unnatural things, they 

 must become weakened. The result is they fall an easy prey to 

 disease, whether it be pathological or parasitical. Is not the main 

 thing to aim at to see to the general health of the trees, to their 

 careful manuring and tending and cleanliness ? Is this always done ? 

 Do not we let things struggle on until the plantation fails under its 

 forced, unnatural living and so falls an easy prey to the parasitical 

 enemies ? All these are points for growers to consider. Certainly 

 " science " ignores these factors in plant sanitation and seems to 

 rush to insect and fungus, to bacteria and enzyme, and recommends 

 washes or spray fluids, often as harmful as the pest one tries to destroy. 

 A great deal has been made of the benefit of treating apple and 

 plum trees with lime and salt. Certainly great results have been 

 obtained where the treatment has been properly carried out, as a 

 means of checking the ""apple sucker" and plum aphis. 



Is this result due to any very definite action on the parasitical 

 disease, or is it due to the production of a certain general healthiness 

 in the trees and a concomitant resisting power to disease ? 



A healthy person resists disease better than one in a cachectic 

 condition, and so it is with man's overcrowded, lacerated fruit trees. 



First we must see to the general healthiness of our plantations, 

 cultivation, manuring, judicious pruning and cleanliness. The pre- 

 vention of insect and fungoid diseases embraces the latter. Two 

 points only need be mentioned in that item of the fruit-grower's 

 work, namely, the destruction by fire of all that we can that is 

 diseased, of old and diseased trees, all winter and summer prunings, 

 all diseased and unhealthy fruit ; and, secondly, to see that all foul 

 growth is kept from the trees by an occasional winter spraying. 



One point the author must mention, in conclusion, namely, that 

 of " natural enemies." The idea of " setting a thief to catch a thief" 

 is one that we can scarcely look up to with great pride, but if one 

 can only set that little murderous insect that destroys another with 

 redoubled energy to work for man's benefit, of course it is a great 

 achievement. There are two cases where this has been done with 

 success, and the result has been that a school of thought has been 

 formulated which claims that we have only to find the natural enemy 

 of this or that parasite (even if we search the world), breed it, turn it 

 loose and then, " hey presto ! " the enemy has gone. Fortunately, 

 this idea has not been received with favour in Britain, nor is it likely 

 to be. We do not hope to live up to the ideal of seeing the fruit- 

 grower (who can scarcely make his way against foreign competition 



