1900J PEAR LEAF-BLISTER MITES. 61 



On May 17th in the past season the following communication, with 

 specimens accompanying, was forwarded to me by Mr. R. Lewis 

 Castle, Manager of the Woburn Experimental Fruit Farm, near Ridg- 

 mont, Aspley Guise, Beds. As will be seen, it draws attention (though 

 without any mention of it being present on Pears in the experimental 

 grounds) to the general prevalence of the attack : — 



" Are the enclosed leaves attacked by Phi/toptus pyri / I am afraid 

 that Pears are suffering rather generally this season from similar 

 attacks." — (R. L. C). 



The specimens consisted of young Pear leaves, mostly about one 

 and a half to two inches in length — measured without the footstalk ; 

 in most cases sprinkled numerously with small blister-galls on both 

 sides of the leaf. These were chiefly of some shade of red, or pale 

 red, sometimes pale green at the edges. The shape of the blister-galls 

 was irregular, being often of small roundish spots, but sometimes 

 forming blotches, as of several galls united. From the young condi- 

 tion of the leafage (particularly after injury in postal transmission), 

 there was some difficulty in observation of the central aperture in the 

 gall beneath the leaf, but by carefully tearing or cutting some of the 

 leaves across, so as to obtain a cross section of the blister, I was able, 

 with the help Of a two-inch focus glass to obtain a clear view of the 

 blister-gall, as a slight elevation on each side of the leaf, with the 

 aperture, or central orifice beneath. 



Some of the leafage on my own wall Pear-trees was very badly 

 attacked ; but as we know the attack to have been prevalent, it is not 

 necessary to give further details of localities of observation. Full 

 accounts will be found in my Annual Reports for 1893 and 1894; and 

 in the latter, at p. 87, I mention that the attack " does much harm in 

 some places, and appears to be steadily increasing, partly by reason of 

 the damage noticeable on the Pear leaves not being so well understood 

 as it ought to be" ; and also because reliable measures for keepmg the 

 attack in check had been (up to date) little known in this country. 



As both of the above-mentioned reasons for continuance of mis- 

 chief which might be easily avoided seem still to continue, it seems 

 desirable to allude to the attack again, and methods found useful in 

 checking it. 



Prevention and Remedies. — The application which appears to 

 have been found most satisfactory is "kerosine emulsion" (for method 

 of preparation of this see Index). I have very good notes of this, sent 

 by an English correspondent, as arresting attack when applied to trees 

 slightly affected, by a Knapsack Strawsonizer early in May ; and also 

 that — in the case of four horizontally trained Pear trees, which 

 previous to the application " had hardly a sound leaf left," and the 



