Dec. 1896.] 



INJURIOUS INSECTS AND FUNGI. 



277 



Injurious. Young trees planted in infested orchards and plan- 

 tations are frequently so injured by the woolly aphides carried 

 to them by the wind, and by the winged females, that they die. 

 Their bark, being tender, is easily pierced by the sharp beaks 

 of the larv?e, and they caunot long withstand these attacks. 



Apple growers often notice bunches of a woolly or cottony 

 substance on the stems, branches, and twigs of apple 

 trees, especially upon scars and cracks where the bark has 

 been injured, or where side shoots and branches have been cut 

 off in an unworkmanlike manner, so that wet has collected and 

 caused decay, and fissures have been formed which have 

 increased in depth and width ; while the edges of the outer 

 layers of bark do not join, and a thin tissue covers the 

 exposed parts. Upon examination, the white substance on these 

 parts will be found to consist of little groups of aphides in various 

 stages, some of which are clothed with fine woolly coverings, 

 and are actively engaged in piercing the denuded surfaces 

 with their suckers, and in feeding on the sap, thus causing an 

 abnormal growth of tissue. Extravasation of sap occurs, giving 

 rise to excrescences and warty growths, which afford food and 

 shelter for the numerous generations of larvse, and, eventually, 

 the whole branch is affected and its vigour and fruitfulness 

 materially impaired. The infestation spreads rapidly to other 

 parts of the tree, and the smaller branches and fruit-bearing 

 spurs are in time attacked. When the twigs and fruit-bearing 

 spurs are attacked, as shown in Fig. 3, they are soon killed 

 by the action of the aphides. After an uninterrupted visitation 

 of these insects, it often happens that the infested tree dies, or 

 becomes useless. 



The effect of this attack is sometimes attributed to " canker," 

 but it is altogether different ; and careful inspection will 

 show that the Woolly Aphis is the sole author of the 

 mischief. It spreads from branch to branch, from tree to 

 tree, and from orchard to orchard, unheeded and unchecked, 

 and it is sheltered and protected by the lichenous and mossy 

 growths upon the trees, and the thick interlacement of boughs 

 and branches unpruned for generations. The Woolly Aphis is 

 occasionally found upon plum trees, especially where they are 

 planted near apple trees, as well as upon elms. 



The Woolly Aphis also infests and injures the roots of apple 

 trees and causes swellings and excrescences upon them. It 

 has been suggested that the aphides merely go under the 

 ground close to the roots for protection from cold ; but the 

 colonies found there were evidently feeding upon the roots. 

 Besides, it is certain that they can bear great cold, as they 

 have been seen flourishing under their woolly coverings in the 

 cracks and crannies of the branches after 1 2 degrees of frost. 



The Aphis belongs to the genus Sckizoneura of the Aphididcp. 

 It is quite distinct from another species of Aphis found upon 

 apple trees, known as Aphis mali, which lives upon the leaves 

 and blossoms. The winged female (Fig. 1), which brings 

 O 93997. C 



