PEAR DISEASES— PEAR PESTS 



1649 



Scab 



Venturia pyrina. 



The pear scab is undoubtedly the most 

 serious fungous disease of the pear known 

 to occur in Oregon. This disease is 

 abundant throughout the western part of 

 the state, especially in the Willamette 

 and Umpqua valleys and in the coast re- 

 gions. It does not occur as a serious dis- 

 ease in the Rogue River valley. It is 

 very similar in nature to the scab of the 

 apple, and the general appearance is the 

 same. Fig. 1 shows well the appearance 

 of the disease upon the fruit. Unlike the 



^ \^ ^ ^'S . \J iiS- 



Pear Scab. 



Fi^. 1. Scab on Fruit of Pear. Badly affected 

 fruit may become cracked as sliown in left 

 hand specimen. 



apple scab, the pear scab causes a disease 

 of the twigs, producing olive-brown cush- 

 ions of tissue beneath the epidermis, 

 which finally break through, giving a 

 rough appearance to the twigs. Fre- 

 quently cankers of some size start upon 

 rapidly growing twigs, which not uncom- 

 monly may be girdled. There is consid- 

 erable evidence to show that on the pear 

 the disease may live over the winter on 

 the twigs. -'.«. 



Cause 



Pear scab is caused by a fungus which 

 is very similar in morphology and life 

 history to the apple scab, but it is due to 

 a different fungus known technically as 

 Venturia pyrina. The summer spore stage 

 of the disease is formed abundantly in 

 the spots on the foliage, fruit and twigs. 

 These are disseminated by the wind and 

 serve to spread the disease. Like the 

 apple scab this fungus produces a sexual 



spore stage on the dead leaves in the 

 spring. 



Treatment 



Since the fungus may live over winter 

 on the decaying leaves, it is advisable to 

 plow early in spring, some time before 

 the trees blossom, in order to bury as 

 many leaves as possible. Smith, in Cali- 

 fornia, has studied the disease, and rec- 

 ommends a dormant spray late in the 

 winter, and further advises spraying 

 twice with Bordeaux mixture while the 

 buds are unfolding. 



In the Willamette valley pear scab has 

 been successfully controlled by the same 

 methods recommended for apple scab. 



Where the disease occurs abundantly 

 on the twigs, as it does particularly in 

 the coast regions, it might be advisable 

 to follow the California method, after 

 previously pruning out as many of the 

 affected twigs as possible. Where or- 

 chards have been neglected, and on this 

 account an abundance of twig infection is 

 present, it is probable that several years 

 of careful spraying will be necessary to 

 bring the disease under control. Under 

 such conditions, severe cutting back be- 

 fore spraying, where consistent with 

 good horticultural practice, will aid 

 greatly in subduing the disease. 



H. S. Jackson 



Sun Scald. See Apple Diseases. 

 Winter Injury to Buds. See Apple 

 Diseases. 



PEAR PESTS 



ApHiDS. See Aphids. 



Apple Leaf Hopper. See Apple Pests. 



Bean Thrips. See Bean Pests. 



Black Scale. 'See Apricot. 



Blight Beetle. See Cherry Pests. 



Blister Mite 



» EriopJiyes pyri Pgst. 



General Appearance 



The work of this mite makes its pres- 

 ence easily distinguishable from all oth- 

 ers. Pear leaves are so affected as to 

 produce reddish or dark-brown spots 

 which become darker with age and may 

 spread so as to entirely cover and destroy 

 the foliage. On the apple the galls re- 



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