Vol. XLIX. LONDON, JUNE, 1917 No. 6 



POPULAR AND PRACTICAL ENTOMOLOGY. 



Two Apple Leaf Mites of Economic Importance. 



by w. h. brittain, provincial entomologist for nova scotia, 



The "Silver-leaf" or "Rusty- Leaf" Mite. 



(Phyllocoptes schlectendali Nalepa.) 



During the summers of 1912 and 1913, which the writer spent 

 in British Columbia, he had an excellent opportunity for observ- 

 ing the work of the mite Phyllocoptes schlectendali Nalepa, this 

 species being extraordinarily abundant in the Okanagan Valley 

 and other parts of the Dry Belt. 



It is most commonly found attacking the leaves of the apple, 

 and though it cannot often be considered a serious enemy of the 

 foliage, the result of its work is conspicuous and peculiar. The 

 presence of the mite makes itself apparent by a decided silvery 

 appearance of the leaves, which, in severe cases, is very pronounced 

 and can be detected from a considerable distance. This appearance 

 is due to the formation of an air space between the epiderm and 

 the palisade cells due to the punctures of the mites. A tree so 

 affected bears a striking resemblance to one attacked by the disease 

 Silver-Leaf. said to be caused by a fungus {Stereum purpureum 

 Pers.) 



This is not the only case in which a silvery appearance is 

 brought about by the work of mites. On plums, bad infestations 

 of Red Spider {Tetranychiis bimacuratiis) produce a somewhat 

 similar appearance, though not so characteristic, and mites feed- 

 ing upon elm leaves have been observed to produce similar symp- 

 toms. It was first thought that all such trees were suffering from 

 Silver-Leaf, which is not surprising, since both these troubles are 

 very abundant in British Columbia and are often present on the 

 same tree. It was only, however, when trees that had been sprayed 

 with nicotine sulphate did not develop the disease that this diag- 



