38 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



ture has been accompanied by drying winds. As the air tem- 

 perature rises, an excessive amount of water is given off through 

 the needles. When water in the stem of a tree or in the soil 

 around it is frozen, an insufficient amount of water is obtained 

 through the roots to replace the water given off by the needles. 

 Lack of water in the plant creates a form of drought which re- 

 sults in winter injury. Mulching in early fall to prevent deep 

 freezmg and to maintain a sufficient amount of water in the soil 

 will aid in preventing winter injury. Small trees in windy or 

 sunny locations may be protected from wind or sun by shields of 

 burlap or other suitable material. Injured trees should be given 

 plant food, as described in the section "Feeding," to stimulate 

 growth. Dead w^ood should be removed after buds open in spring. 



ASH 



Ash trees occasionally are affected with anthracnose, leaf 

 spot, scorch, powdery mildew, rust, wood rot, and a few minor 

 canker and dieback diseases. 



Anthracnose. — Ash anthracnose, caused by the fungus 

 Gloeosporium aridum, results chiefly in destruction of leaf tissue. 

 It produces large, irregular brown areas, especially numerous 

 along the margins of the leaves. It is neither abundant nor de- 

 structive in Illinois during most years, and, except in unusual 

 cases, requires no treatment. It can be controlled by sprays of 

 organic mercury or copper fungicides (Table 1, end of circular). 

 One or two applications of spray should be effective. Leaves from 

 affected trees should be burned in autumn to eliminate the main 

 sources of overwintering inoculum. 



Scorch. — Many ash trees show leaf scorch annually, espe- 

 cially trees growing under adverse conditions. Some affected 

 trees may lose their leaves and appear dead by August. Scorch 

 is discussed under "Types of Tree Diseases." Feeding and water- 

 ing to stimulate root growth and pruning to reduce total foliage 

 growth may aid trees to overcome scorch. 



Rust. — Rust, caused by the fungus Puccinia peridermio- 

 spora, occurs occasionally on leaves of ash trees, but it is usually 

 of very little significance. It causes distortion of leaves and 

 swelling of twigs. The alternate hosts of this rust are marsh and 

 cord grasses. Rust appears infrequently and causes insufficient 

 damage to require control treatment. Eradication of marsh and 

 cord grasses near ash trees will disrupt the life cycle of the 

 fungus. 



