278 [ DISEASES OF THE APPLE TREE 



Two species of Acari are frequent on the leaves of 

 the apple, viz : Phytoptus Mali Am. which produces an 

 erinosis on the undersurface of the leaf, and Typhlodro- 

 mus Mali Am. which also attacks the young leaves 

 causing the formation of large blisters which afterwards 

 turn deep red and then brown. Another species, Phyl- 

 locoptes Schlechtendali Nal. is far less common and causes 

 a part of the leaf or the whole of it to become discoloured 

 and then to turn brown and dry. 



Among the Coccideae there are several scales which 

 are injurious to the apple tree. The most important is 

 Mytilatpis pomorum Bche, the mussel scale of the apple, 

 which is frequent on the apple in sheltered nooks and 

 close situations. Lecanium Oleae L. and L. Mali Schrk. 

 a closely allied species, but larger and more elliptical 

 in shape and of a whitish brown colour, are sometimes 

 found on the apple. ( eroplastes Rusci Targ., the fig- 

 tree scale, is rather frequent on the apple but never 

 dangerous. Dactylopius Citri is also frequent in certain 

 years, and attacks the apple in the same way as the 

 pear. 



Three species of Aphis are found on the apple. 

 Aphis Mali Fab. of- which the wingless insect is light 

 green with a reddish head, the winged insect being 

 black with green abdomen. This species is common 

 on the apple, and particularly on the young suckers 

 around the base of the stem. It is often very troublesome, 

 considerably weakening the tree, and when an attack 

 commences early in the season, prevents the fruit from 

 setting or causes it to be shed off as soon as it sets. 

 Aphis Piri Koch, and A. Srbi Kalt. are rarer. The 

 first has wingless insects of a chocolate colour with 

 darker thorax or back, and winged insects yellowish 

 green, spotted black. The wingless insect of the second 

 species is yellowish green or brown yellow, powdered 

 bluish grey, and the winged insect is dark brown or 

 black. An attack of any of these species of Aphis 



