•34 



THE BEPOKT OF THE 



No. 36 



and this appears to be the earliest record of its appearance in North America. 

 Since then, it has been reported from Pennsylvania and Connecticut (2) and 

 last slimmer (1921) specimens of the mite were forwarded to us from Vernon, 

 B.C. 



The spider mite occurs in all the fruit growing districts of Ontario, but is 

 especially troublesome in the Niagara district. In view of its wide-spread occur- 

 rence in this province, it appears to the writers that it must have been introduced 

 many years before its discovery, and that it must have a much wider distribution 

 in North America than that recorded in literature. It is highly probable that 

 in many cases P. pilohts has been mistaken for the common red spider T. telarius 

 or for the clover mite Bryobia pratensis and has been reported under one or the 

 other name. % 



Host Plants and Nature of In.tuey. 



We have taken the mite on European and Japanese plums, apple, sour and 

 sweet cherries, pear and peach. According to Caesar, it also occurs on hawthorn, 

 and Carman (3) records its occurrence on rose. The European plum is by far 

 the favourite host plant with apple next and then sour cherry. In Connecticut 

 the mite has caused severe injury to apples, particularly Baldwin trees, but in 

 Ontario it has proved to be, so far, only of importance as a pest of European 

 plums. 



In the Niagara fruit belt, the mite is one of the major pests of the plum 

 orchard. It attacks both surfaces of the leaves and, by means of its mouthparts, 

 punctures the tissues and withdraws the plant juices. At first this results in a 

 speckling of the leaves, due doubtless to the withdrawal of chlorophyll. Later 

 on, if the infestation is severe, all the leaves become pallid, ■ sickly in appearance, 

 tough and largely funetionless. From a distance the foliage on badly attacked 

 plum trees looks as if it were coated with road dust. 



The injury to the leaves naturally robs the trees of vigour, and, when 

 severe, checks the growth of the wood, dwarfs the fruit and retards its ripening. 

 Two years ago the following data (table No. 1), showing the loss in weight and 

 size of fruit and in growth of wood due to mite injury, was secured by comparing 

 the trees in an infested block of plums with those in an uninfested block. The 

 trees were the same age, and were grown under the same conditions, apart from the 

 fact that the uninfested trees had been sprayed with lime sulphur and the others 

 with bordeaux mixture. 



TABLE No. 1 — Showing Loss in Weight and Size of Fruit and in Growth of Wood 



Due to Mite Infestation 



Variety 



Gueii 

 Pond's 

 Lombard 

 Reine Claude 



Loss in Weight of 

 Fruit 



41.5% 

 20.6% 

 27.3% 

 28.7% 



Loss in Size of 

 Fruit 



40.3% 

 24.3% 

 19.1% 



24.8% 



Loss in Terminal 

 Growth of Wood 



23.9% 

 45.6% 

 22.3% 

 35.0% 



On apple trees, according to Garman, the infested foliage becomes brownish or 

 assumes a dull leaden appearance, and later in the summer many of the leaves 

 drop. The same author reports a marked reduction in the size of the fruit on 

 infested Baldwin trees. 





