THE PEAK PSYLLA* 



P. J. PARROTT and H. E. HODGKISS. 



The psylla is one of the principal enemies of pear orchards, and 

 in many localities of the State it is the most troublesome if not the 

 most destructive insect pest of this fruit. It has ruined many crops 

 of pears and has so weakened large numbers of trees that they 

 have easily succumbed to winter-killing. 



NATURE OF INJURY. 



Severe damages to pear trees occur during periods of the super- 

 abundance of the psylla. The injuries are due primarily to the loss 



Fig. 26. — Leaf cluster showing nature of injury by nymphs of pear psylla. 



of plant juices extracted by myriads of the tiny insects which feed 

 on the stems of leaves and fruits. The work of the first brood of 

 larvae or nymphs during the latter part of May or early in June, at 

 the axils of the tender leaves and young fruits or on the under sides 



* Reprint of Circular No. 20, January 22, 1913. 



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