THE PEAE LEAF BLISTEE 



WE have several times received 

 from subscribers in various 

 parts of our province, samples 

 of pear leaves having black corky spots upon 

 them, and these were either a mystery to the 

 senders, or else supposed to be either leaf 

 blight, or scab. After consultation with 

 Prof. Fletcher, of the Central Experimental 

 Farm, we were able to reply that the cause 

 of the trouble was a minute mite (Phytoptiis 

 pyri), belonging to the same order (Acarina) 

 as the cattle tick, and the itch spider. Fig. 

 2600 shows an adult mite, greatly magnified. 

 Indeed, these mites are so small that they 

 cannot be seen without a glass, and to study 

 their structures a first-class microscope" 's 

 necessary. 



Bulletin 61 of the- Cornell 

 Experimental Station, gives a 

 most excellent account of this 

 mite, written by Prof. Slinger- 

 land. To give an idea of 

 their diminutive size, he says 

 that it would take 150 

 of them placed end to 



really galls, produced by these mites, and 

 within them the eggs are deposited ; they are 

 quite easily distinguished from the fungus 

 spots by their blister-like corky appearance. 



Fig. 2601. 



Fig. 2601, from the bulletin referred to, 

 shows a highly magnified section of a pear 

 leaf through one of these galls, g, showing 

 gall ; n, n, normal structure of leaf ; o, open- 

 ing of the gall ; and e, eggs of the mite. 



Fig. 2600. Pear Leaf Blister Mite. 



end, and 600 side by side to measure an 

 inch. These tiny mites winter underneath 

 the outer scales of the buds, fifteen or 

 twenty having been found underneath a sin- 

 gle bud scale. Thus situated, they are 

 ready for mischief early in the spring. 

 The diseased portions of the leaves are 



Fig 2602. 



Later in the season the galls dry and turn 

 brown or black, and are more conspicuous 

 on the lower side. The leaf in the mean- 

 time has shrunk to its normal thickness, as 

 shown in Fig. 2602, in which g is gall, 

 n, n, uninjured portion of leaf, and 0, open- 

 •ing to gall from under side. 



Various remedies have been experimented 

 with, but the most successful one, according 

 to Prof. Slingerland, is a thorough sprayiiig 

 in winter with kerosene emulsion diluted 

 with from five to seven parts of water. Ap- 

 ply from every side, so as to reach all au- 

 tumnal buds, for it is about them the blister 

 mite is most abundant. 



