March 1895.] 



INJURIOUS INSECTS AND FUNGI. 



301 



Apple-growers may have frequently noticed bunches of a 

 woolly or cottony substance on parts of the stem, branches, and 

 twigs of apple trees, especially upon scars where the bark has been 

 injured, or where side shoots and branches have been cut off in an 

 unworkmanlike fashion, and the cuts made slanting upwards 

 instead of downwards, so that wet has collected and caused 

 decay, and cracks have formed which have increased in width and 

 depth. The edges of the outer layers of bark do not join, and 

 a thin tender tissue covers the exposed parts. Upon examination, 

 the woolly substance upon these- parts will be found to consist of 

 little groups of larvse clothed with fine woolly coverings, actively 

 engaged in piercing these denuded surfaces with their suckers, 

 and feeding on the sap, causing abnormal growth of tissue. 

 Extravasation of sap occurs, giving rise to excrescences and 

 warty growths, affording food and shelter for the numerous gene- 

 rations of larvae, and eventually the whole branch is affected, 

 and its vigour and fruitfulness materially impaired. The 

 infestation spreads to other branches, and the smaller branches 

 and fruit-bearing spurs are attacked. After an uninterrupted 

 attack of these insects it often happens that the infested tree 

 dies or becomes useless. Young trees are sometimes so weakened 

 by the suckings of numerous woolly aphides that they do not 

 recover. 



The result of this infestation is often said to be " canker," 

 occasioned by climatic influences, unsuitable soil or subsoil, or 

 too much, or improper, pruning. But it is altogether different 

 from canker, and close inspection will prove that the woolly 

 aphis is the author of the mischief. Old neglected orchards, as 

 too many unfortunately are, swarm with American blight, 

 which has spread from branch to branch, from tree to tree, and 

 from orchard to orchard, borne by the wind, unchecked and 

 unheeded. It is sheltered by the lichenous and mossy growths 

 upon the trees, and the thick interlacement of boughs and 

 branches unpruned for generations. 



Young trees planted in infested orchards and plantations are 

 often ruined by the woolly aphides, brought by the wind or 

 by the winged females. The bark of these trees is tender and 

 easily pierced by the sharp beaks of the larvae, and cannot long 

 withstand their attacks. 



Not only does the woolly aphis infest the stems and branches 

 of the apple trees, but it also descends to the roots and feeds 

 upon them, causing swellings, and injuring them in the same way 

 as the upper parts of the tree. It has been suggested that the 

 aphides merely go under the ground for shelter from cold, but 

 the colonies found there were evidently engaged in extracting 

 the juices from the roots. Besides, it has been proved that 

 they can bear great cold. They have been seen flourishing 

 under their woolly coverings in the cracks and crannies of the 

 stems and branches after 12 degrees of frost. 



