82 



THE REPORT OF THE 



No. 38 



Natuee of Injury. 



The ])sylla causes injury by extracting with its sucking mouth-parts the saj) 

 from the leaves, leaf ])etioles, fruit stems, and tender wood on which it feeds. 

 On badly infested trees, the continual sapping of the life juices by myriads of 

 insects robs the tree of vitality, dwarfs the. fruit, produces brown, dead areas on 

 the leaves (Fig. 14) and, in extreme cases, causes the foliage to drop prematurely. 

 Trees seriously weakened by this pest are especially susceptible to winter injury 

 and in a hard winter like that of 1917-18 readily succumb to low temperatures. 



Large quantities of a sweet sticky liquid called honey-dew are excreted by the 

 psyllas, and on attacked trees the foliage, fruit, twigs and branches may be covered 

 with this sticky material and with a sooty fungus which grows in it. (Fig. 15). 

 This coating of honeydew and sooty fungus not only makes the trees and fruit 

 very unsightly but it is very probable that it is also detrimental to the physiological 

 functions of the leaves. 



Fig. 14. — Leaf injury caused by 

 pear psylla. 



Fig. 15. — Leaves showing honey-dew funsus and 

 nymphs. 



Life Histoky, 



Summary. 



The winter is passed in the adult stage. The adults hibernate under the rougli 

 bark on the trunks and main limbs, and under grass, leaves and rubbish near the 

 infested- pear trees. In late March or early April the insects leave their winter 

 quarters, congregate on the twigs and fruit spurs and in a short time, provided 

 the weather remains propitious, commence to lay eggs. Oviposition may continue 

 until about the time the petals drop; however, the vast majority of the eggs are 

 laid by the time the fruit buds have burst. The eggs are deposited on the twigs, 

 fruit spurs and smaller branches, chiefly on the under surface. They commence 

 to hatch when the fruit buds are beginning to break, and nearly all have hatclicd 



