CARTER: ILLINOIS TREES: THEIR DISEASES 



63 



arbor-vitae, cypress, and false-cypress. The fungus invades and 

 kills the bark, and in time cankers form on the diseased stems. 

 As the cankers enlarge, the affected stems die and the needles 

 turn brown. Young trees that are affected may die. All diseased 

 twigs and branches should be removed and burned. In nursery 



Fig. 59.— Fruits of hawthorn affected with cedar-quince rust may 

 be deformed in shape, dwarfed in size, and have orange to cream tubelike 

 structures projecting from their surfaces. 



plantings, all affected plants should be destroyed. When avail- 

 able, resistant varieties such as Hill juniper, Keteleer red cedar, 

 and spiny Greek juniper should be used. Spraying with organic 

 mercury or copper sulfate and hydrated lime (Table 1) may pre- 

 vent infection. Five sprays applied at 10-day intervals are recom- 

 mended. The first application should be made as soon as shoot 

 growth starts in the spring. 



LINDEN 



Linden is relatively free of diseases; however, Verticillium 

 wilt affects an occasional tree, and some affected trees die. 



Verticillium Wilt. — This vascular disease is caused by the 

 fungus Verticillium alho-atrum. In linden, it causes leaf and 

 branch wilt, which are accompanied by the production of brown 

 streaks in the young sapwood of affected branches. These streaks 



