DISEASES OF THE PEAR TREE ] 241 



black. The other mite, Phytoptus Mali Am., is less 

 frequent on the pear but common enough on the apple. 

 It produces hairy spots of silvery white colour on the 

 undersurface of the leaf. These hairy white spots are 

 situated in a depression of the surface, which corresponds 

 to a blistered condition of the upper surface, and 

 gradually increase in size until they coalesce, often 

 extending to the whole undersurface of the leaf (erinosis). 

 These spots later on become reddish brown or brown. 

 The diseased leaves should be picked and burned. 



There are three species of Aphis known to attack 

 the pear tree. The most frequent is Aphis Mali Fab. 

 of which the wingless insect is light green, with a 

 reddish head, and the winged insect is black, with a 

 green abdomen. This Aphis is very common on the 

 apple and often jeopardizes the crop very seriously. 

 It is less common on the pear, but still it is the species 

 more frequently met with on this tree, although the 

 infestation is never so general or so severe as in the 

 case of the apple. The next in importance is Aphis 

 Piri Koch, of which the wingless insects are light 

 reddish brown, covered with a mealy powder, the winged 

 insects being greenish yellow spotted black. This Aphis 

 is much more dangerous to the pear than the preceding 

 species, curling up and destroying the foliage with great 

 virulence, and unless properly treated repeats the same 

 havoc year after year on the same tree. However, it 

 is fortunately rather rare, and it does not seem to 

 extend rapidly from tree to tree. The third species 

 is Aphis piraria Pass, of which the wingless insect is 

 black, and the winged insect is greenish brown with 

 a black, head and thorax. This Aphis has not been 

 noticed as yet on our pear trees. As a remedy against 

 the Aphis it is recommended to spray the tree when 

 in leaf wirh a solution of tobacco juice or with a 

 i per cent solution of lysol, or dusting repeatedly with 

 precipitated sulphur containing nicotine (Schloesing's 

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