158 ORCHARD INSECTS 



weakened, making little growth and sometimes dropping both 

 leaves and fruit. 



Control. The psylla may be largely controlled by spraying 

 with lime-sulfur and in bad cases there should be an application 

 of this wash just as soon as the leaves are off the trees in the 

 autumn. This ought to be followed by another application in 

 the spring and both of these should be of such a strength as to 

 do thorough work. If the specific gravity hydrometer test is 

 made, 1.03 is the proper strength after diluting. About one 

 gallon of commercial lime-sulfur to 9 or 10 gallons of water 

 will usually produce this strength. Where the dormant spray- 

 ing has been neglected, or if the insects are plentiful in spite 

 of winter spraying, some summer applications must be made. 

 Any of the contact sprays are likely to be useful, but some 

 of the tobacco extracts seem to be most efficient. If this summer 

 spraying can be done just after a rain has washed off the honey- 

 dew so much the better. 



Leaf Blister Mite. Another pest which is frequently trouble- 

 some on both pears and apples is the blister mite. This is not 

 a true insect, but is related to the red spider of plants and to 

 the mite which causes "scab 1 ' in sheep. It is entirely too 

 small to be seen without the aid of a microscope, so that the 

 orchardist is never likely to see it, but if he lives in an infested 

 district he is likely to become altogether too familiar with its 

 work. 



Habits and Injuries. The winter is passed in the adult stage 

 under the scales of the buds, where the mites collect in large 

 numbers. As soon as the leaves begin to expand in the spring 

 they are entered by the adults and the eggs are deposited in the 

 leaf tissues. The eggs soon hatch and the old and young feed 

 upon the cells of the leaf, causing the galls or blisters which are 

 very characteristic. 



These are at first light-colored in the apple and reddish in the 

 pear, but later turn brown when dead. This is the most notice- 

 able and distinctive stage of the injury and is easily recognized 

 by anyone who once becomes familiar with it. The small brown 

 blisters are scattered somewhat regularly over the surface of 



