SHADE TREES. 



191 



FIG. 63. Oyster mush- 

 room (I'leurotus 

 anpidu*} on maple, 

 following injury. 



MAPLE (Acer). Leaf spot (PhyUosticta acericola C. & E.) forms irregular 

 brownish .spots on the leaves of the rock and white maples. 



Anthracnose (Glarosporium apocryptum E. & E.) is known to cause serious in- 

 jury to the leaves and shoots of the box elder. and maple. 

 Leaf spot (Rhytisma acerinum Fr.) is characterized by 

 conspicuous black spots on the leaves of the red and white 

 maples, but is practically harmless. 



Xectria cinnabar ina (Tode) Fr., a common fungus char- 

 acterized by small cinnamon-colored pustules occurring on 

 dead wood, follows winterkilling, sun scald, etc. It is 

 especially noticeable on winterkilled twigs of Norway 

 maples. 



Oyster mushroom (Pleurotus sapidus Fr.) is a large, 

 edible fungus growing in masses on maples that have been 

 injured by borers and other agencies. A mildew (Uncinula 

 circinata E. & E.) sometimes infects the leaves of various 

 maples. 



Sun scald and frost cracks are not uncommon on 

 maples. The rock maple is one of the most susceptible 

 trees to sun scorch and "bronzing" of foliage induced by 

 excessive transpiration during dry periods. The red maple 

 is susceptible to winter injury of roots, and like the rock 

 maple suffers from drought. 



HORSE-CHESTNUT (JSscu-lus). Leaf spot (PhyUosticta 

 sphceropsoidea E. & E.) appears in the early summer, and 



later causes a conspicuous yellow spotting of the foliage. This disease is more or 

 less common every year. The leaves of the horse-chestnut are occasionally affected 

 with mildew (Uncinula flexuosa Pk.), and the 

 winterkilled twigs are sometimes attacked by 

 Xectria cinnabarina. 



CHESTNUT (Castanea). This is seldom 

 planted as a shade tree, although it is some- 

 times seen on country roadsides and on lawns. 

 The chestnut blight, which is so serious and so 

 universally distributed at the present tune, 

 renders the use of the species as an ornamental 

 tree out of the question. The chestnut is also 

 affected with certain leaf spots, etc. 



AMORE (Platanus). The tree most likely 

 to be severely defoliated by a fungus is the 

 sycamore. The causal organism is Gloeosporiurn 

 -cquum (Fckl.) Sacc., which affects the 

 petioles and veins of the leaves, causing small 

 black areas on these organs. More or less large 

 portions of the leaves turn brown and the leaf 

 finally falls. 



The sycamore is unusually susceptible to 

 winterkilling of the twigs, but in spite of this 

 :int defoliation and twig killing it is a very 

 hardy tree. 



POPLAR (Populus). The principal species 

 in cultivation as shade trees are the Carolina 

 poplar, white poplar, Italian poplar and the 



Lombardy poplar. The Italian poplar is often severely affected with rust 

 (Mdampsora populina (Jacq.) Lev.), and a mildew (Uncinula salicis DC. Wint.) 

 is frequently observed on the leaves of poplars. Anthracnose (Marssonia populi 



FIG. 64. Horse-chestnut leaf spot 

 (1'hyllosticta). 



