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These so-called new pests, either insects or fungi, are as ancient 

 as the world, and although they are greatly influenced by their im- 

 mediate surroundings, by the food at their disposal, the climate in 

 which they live, by the enemies they have to contend with, and by 

 many other circumstances of various nature, they nevertheless spring 

 from parent individuals in every respect like themselves. The 

 devastating phylloxera, for instance, or the woolly aphis of our 

 days did not originate as spontaneously from the roots of the vine 

 or of the apple tree, but are the decendants, in a direct line, of a 

 long list of ancestry of lice of these respective tribes. In a similar 

 manner, the rust of cereals or the oidium of the vine have no more 

 budded from the wheat plant or the grape vine than potatoes are 

 transformations of the soil, but have simply grown from seedlike 

 germs produced by preceding pests of the same kind. 



Every season, almost, we hear of the appearance of new pests, 

 and it is more than likely that, for a great number of years to come, 

 the list, already formidable, of the sorts of insects and fungi that 

 invade and prey on our crops will gradually be made longer still, 

 by the addition of more unwelcome enemies. 



Various factors combine to bring about this undesirable state 

 of things. 



In the first instance, we have seen that new conditions of life 

 may develop propensities of a distinctive nature ; or, again, the 

 partial extermination of some parasites of these pests, either owing 

 to unfavourable surroundings or the use of insecticides, by break- 

 ing the balance of nature, may insure the preponderance, to an 

 alarming degree, of certain species of pests. By the constant and 

 more rapid interchange, on the other hand, of plants, fruits, seeds, 

 and cuttings of all sorts of ornamental, economic, or useful plants, 

 from all parts of the world, many of the parasites of plants have 

 been widely disseminated, without, in a great many instances, their 

 own particular parasites having been brought with them ; and thus 

 the appearance of hitherto unknown pests is accounted for in 

 countries until then free from them. 



For, as it is so concisely expressed in Dean Swift's oft quoted 

 couplet 



The little fleas that do us tease 

 Have other fleas that bite "em ; 

 And these, in turn, have other fleas, 

 And so on ad infinitum. 



To ward against the importation of noxious pests, the Govern- 

 ment of Western Australia, profiting by the errors and the 

 experience of older fruit-growing countries, have passed a Fruit 

 Pest Act, reproduced, as an appendix, in this Handbook, and 

 which provides for the disinfection, on landing, of plants and fruits, 

 for the purpose of checking any possible importation from abroad 

 of pests inimical to fruit trees and vines. 



Amateur gardeners, as well as professionals, who concern them- 

 selves about the well being of their plants, have continuously to 



