The Pear Psylla. 107 



infested for 15 years, and, yet, it had not appeared (in 1892) in one 

 orchard set in 1881 only half a mile distant. 



Our New York nurserymen are reported to be responsible for 

 its introduction into Maryland, Virginia, New Jersey and Canada. 

 In nearly every case it is claimed the source of infestation can 

 be directly traced to pear stocks bought of New York nurserymen 

 in 1890 or 1891, or about the time the pest was so numerous in 

 this State. It -is supposed that the hibernating form of the insect 

 is thus distributed. 



Its Classification and Name. 



This pear pest is one of the true bugs and belongs to the family 

 Psyllidae^ commonly known as jumping plant-lice from the leaping 

 habit of the adult insects. Thirty-four species of Psyllids have 

 thus far been described from the United States. 



Psylla pyricola, although it was observed in this country in 

 1833, received its name in Europe fifteen years later. Previous to 

 184:8, European writers had referred to the species as Psylla pyri^ 

 not distinguishing it from that species. Psylla jpyricola sometimes 

 attacks the apple-tree in Europe, but it seems to confine its attacks 

 to the pear in this country, 



[ndications of its Presence. 



During severe attacks of this pest, old trees put forth but little 

 new growth, new shoots often droop and wither in May, the leaves 

 turn yellow and the fruit grows but little, and in midsummer the 

 leaves and half-formed fruit often fall from the trees. The insect 

 also indicates its presence by secreting large quantities of a sweet, 

 water-like, sticky liquid called " honey dew " which often covers 

 all parts of the tree ; it has literally rained from the leaves in some 

 cases and smeared the backs of horses during cultivation*. A 

 black fungus soon grows all through this honey-dew and thus gives 

 the tree a disgusting blackish appearance as if treated with a thin 



* During the severe attack in Maryland in 1894, " the leaves were 

 scarcely at all yellowed, but were covered with dead and dry patches or 

 spots, sometimes invading almost the entire leaf." It seemed to be due 

 " to the sun-sealding resulting from the collection of the honey-dew on the 

 leaves in large drops." 



