98 SHADE TREES. 



penetrate the foliage, except so far as may be necessary for 

 the formation of holdfasts, but spread over the 

 surface of the foliage forming a delicate white 

 web which has much the appearance of dust. 



One of the most important of these mildews is Micro- 

 sphceni aim (Wallr.) Wint. which attacks lilacs and also 

 occurs on the oaks, birches, dogwoods and some other plants. 

 Another very common mildew is Uncinula solids (D. C.) 

 Wint. which occurs on the poplars and willows. As a rule, 

 they do not appear until late in the season and cause very 

 little injury except to young trees and nursery stock. 



Treatment. 



Spraying with potassium sulphide (1 Ib. to 50 gal. of 

 water) is an efficient remedy. 



LEAF CURL. 



The leaf curls are more or less common on many trees, the 

 most conspicuous being the one on the peach. The most im- 

 portant one on forest and shade trees is due to Taphrina 

 Attacks ccerulescens (Mont, and Desm.) Tul. which 



oaks - attacks the oaks causing the leaves to appear as 



though blistered. It is not often injurious but sometimes 

 causes death of trees which have been affected for a number 

 of years. 



Treatment. 



The burning of fallen leaves and spraying the trees with 

 copper sulphate or lime-sulphur when dormant will practi- 

 cally eliminate the pest. 



