INJURIOUS INSECTS AND DISEASES 283 



leaf along the main veins and around the edges, showing that the diiEculty is 

 one which affects the entire leaf, and not any particular part of it. In general 

 there is a tendency for the foliage in plants so attacked to wither up and hang 

 on the tree for a time. There are no specific treatments for troubles of this 

 sort. The diseased plant or parts must be cut away and burned. All the 

 conditions which seem to favour the development of the disease must be re- 

 moved. Careful management in matters of sanitation is often much more 

 important than any attempt at specific treatment. 



Injurious insects follow swiftly on the heels of disease, and disease is usually 

 further strengthened by the destructive agency of insect pests. 



So far as our experience shows, the protection of our fruit crops from insect 

 ravages is likely to be an increasing difficulty, consequent on the increasing 

 extent of the areas in which one kind of orchard tree or fruit bush is grown 

 year after year, thus giving every opportunity for the established settlement of 

 the insect feeders on that special crop. 



APPLE 



Under proper treatment the apple tree is rarely affected by either disease or 

 insects. It is chiefly when injured by mismanagement, starved for want of 

 plant food, or too heavily cropped, that trouble ensues. Soil and climate are 

 powerful factors in the production of apple disease, and also frequently invite 

 the attacks of insects. The chief causes of injury may, therefore, be stated to 

 be over-luxuriance or weakness of growth. 



The chief diseases that attack the apple are canker, mildew, and American 

 Blight. The first is caused by bad drainage, the second arises from many and 

 the most opposite causes, such as improper manuring, over-cropping, excess of 

 heat or moisture. 



The attack of the woolly apple aphis, commonly known as American 

 Blight, may be taken as an example of orchard infestation which is exceedingly 

 common, and is very injurious by destroying the health of the tree, and yet at 

 the same time is so open to remedy that it may with little expense or trouble 

 even be stopped at the outset. The presence of the apple bark plant louse or 

 woolly aphis may be easily detected by the cottony growth on the insects, giving 

 the appearance of a white film. When there are many it appears as if a knot 

 of cotton wool were sticking to the bough or even hanging loose in pieces 

 several inches in length. 



With regard to remedies ; soft soap, tar, or, in fact, anything oily, greasy, or 

 sticky that can be well rubbed on, and which by adhering for a time will choke 

 all the aphides that it touches, will be of use. 



Other insects that attack the apple are the green-fly {Aphis malt), codlin 

 moth [Carpocapsa pomonella), blue-head caterpillar {Diloha caruleocephala), goat 

 moth {Cossus ligniperda), lackey moth [Bombyx neustria), lapped moth [Gastro- 

 pacha quercifolia), small ermine moth [Hyponomeuta padeUus), apple saw-fly 

 [Hoplocampa testudinea), and apple blossom weevil {Anthonomus pomorum). 



Of all these pests probably the codlin moth is most frequent and persistent. 



