THE PEAR PSYLLA AND ITS CONTROL.* 



F. H. HALL. 



Probably the most troublesome insect attacking 

 A serious the pear is the psylla. These tiny creatures are 

 pear pest similar in many ways to aphids and are some- 



times called jumping plant lice. They are 

 sucking insects, like plant lice, and like them ; they multiply rapidly, 

 producing several broods each season, so that, unless checked, they 

 make up in numbers what they lack in size, and may injure the pear 

 trees very severely. The larvae, or nymphs, of the first brood, in 

 early spring cluster about the axils of the leaves or young fruits 

 or work from the under side of the tender young leaves and suck 

 out so much sap that growth is checked just when it should be 

 greatest. The leaves become stunted and sometimes fall, and the 

 fruit ceases to grow in size and may drop prematurely if the work 

 of this first brood is continued by the later broods. In long-continued 

 attacks the trees may become almost defoliated, and the new leaves, 

 if they appear, are generally few in number and pale in color. With 

 the injury caused by the draft on the sap of the tree, there is joined 

 an external disfigurement of both leaves and wood due to the copious 

 secretion of honey-dew by the psylla, which serves as food for the 

 " sooty fungus." Growth of this fungus soon gives the wood a 

 smutty, discolored appearance and darkens and stains the leaves. 

 If the attacks of psylla are severe the trees go into winter in 

 a weakened state and succumb much more readily to low tem- 

 peratures than do uninjured trees. Renewed attacks, year after 

 year, so lessen the vitality of the trees that they become profitless 

 cumberers of the ground. 



The mature psylla flies (Plate I, fig. 4) of the 



Life history last fall brood pass the winter on the trees or in 



of pear psylla protected places about them; and appear not to 



become completely dormant until permanent low 



temperatures have been reached. During late November and early 



December, a rise in the daily mean temperature to only a few degrees 



* Reprint of Popular Edition of Bulletin No. 387; for Bulletin see p. 422. 



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