54 MISC. PUBLICATION 16 8, U.S. DEPT. OF AGRICULTURE 



CONTROL 



The blister mite can be controlled by thorough spraying during 

 the dormant period, with winter-strength lime-sulphur, as for the 

 San Jose scale. Oil sprays applied during the dormant season are 

 less satisfactory, although fairly good results have been obtained by 

 using them in warm periods in the spring after the buds have begun 

 to swell (39, 67, m, 201). 



PEAR-PSYLLA INJURY 



Pears injured by the pear psylla (Psyllia pyricola Foerst.) are 

 black in appearance, the result of the growth of a black fungus on 

 the sweet honeydew produced by the insects, which also cause serious 

 injury to the foliage and young growth. The psylla is a tiny, 

 cicadalike insect, about a tenth of an inch long when full grown. 

 Adults hibernate in cracks in the bark of the trunk and limbs, under 

 bark scales, or under trash on the ground in and near the orchard, 

 and migrate to the trees with the verj^ first warm days of early 

 spring. Applications of 3 percent lubricating oil emulsion at this 

 time have given ver}^ satisfactory results. Many of the adult flies 

 are killed, and the film of oil on the bark appears to have a great 

 deal of residual value, reducing the number of eggs laid and killing 

 a high percentage of the young psyllas that hatch. Nymphs of 

 the first brood congregate mostly in the axils of the young leaves and 

 fruit and may be treated witK a nicotine-soap spray, applied just 

 after the blossoms have fallen, lead arsenate being added for the 

 codling moth.^ 



PINK-MOLD ROT 



(See Apples, Pink-Mold Rot, p. 37, and pi. 16, C) 



POWDERY MILDEW 



(See Apples, Powdery Mildew, p. 38) 



RHIZOPUS ROT 



(See Apples, Rhizopus Rot, p. 40 and pi. 13, B) 



SAN JOSE SCALE INJURY 



(See Apples, San Jose Scale Injury, p. 40. and pi. 19) 



SCAB 



(Venturla pyrina Aderh) 



Scab on pears (pi. 16. A. B) is similar to the disease of the same 

 name on apples, although the two are caused by different species of 

 the same fungus. Pear scab usually occurs as larger, rougher spots 

 on the fruit than are common for apple scab and occurs more fre- 

 quently on the twigs than does apple scab. On Seckel and possibly 

 on other varieties very small scab spots sometimes occur that may 

 be mistaken for other blemishes if not carefully examined. 



« See statement regarding lead arsenate spray residue, under Codling-Moth Injury, p. 21. 



