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Article " Entomology " in Encyclopedia Britannica, 



XI ed 



THE PEAR PSYLLA IN ONTARIO. 



W. A. Ross, DoMiNiox Entomological Laboratory, Vinelaxd Station, 



The following paper is based largely on insectary and orchard investigations 

 which were conducted at the Dominion Entomological Laboratory at Vineland 

 Station, Ontario, in 1917 and 1918. In the insectary the psylla was bred on 

 pear seedlings grown in flower pots and covered with lantern chimneys. 



History and Distribution. 



It is believed that the pear psylla (Psylla pyricola) was first introduced into 

 North America in 1832 on pear trees imported into Connecticut from Europe. 

 According to Slingerland and Crosby,* the insect is now generally distributed 

 over the Eastern United States a3 far south as Virginia, and it also occurs in 

 California. 



It was first discovered in Canada in 1894 at Freeman, Ont., at which place 

 it was found seriously injuring a block of three hundred Dwarf Duchess pear 

 trees. Since then it has been recorded from other parts of Ontario, from Nova 

 Scotia, and from British Columbia. Professor Lochhead informs me it has never 

 been taken in Quebec. 



In British Columbia, according to Mr. R. C. Treherne of the Dominion 

 Entomological Branch, the psylla is present only in the lower Kootenay country 

 where it was first observed in the spring of 1917. As the B.C. form occurs only 

 on apple and as it differs slightly from its Eastern fellow, there is room for doubt, 

 in my mind at least, as to its being P. pyricola. 



Professor W. H. Brittain, Provincial Entomologist for Nova Scotia, informs 

 me that in that province the pear psylla is injurious in some years and in other 

 years it is ver}^ little in evidence. 



In Ontario the insect has been taken in the counties bordering Lake Erie 

 and Lake Ontario as far East as Trenton. However, outside of the Niagara and 

 Burlington districts (where it is only too frequently very destructive), it is of 

 comparatively little importance. 



Our observations indicate that, in this province at least, the psylla is primarily 

 a pest of the large orchard or of sheltered orchards. For reasons at present not 

 clear to us, conditions in small plantings do not seem to be favorable for its rapid 

 multiplication and in such places it seldom attains destructive proportions. 



*Manual of Fruit Insects. 



6-E. 



