82 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



REDBUD 



Redbud is affected occasionally by a canker disease and by 

 a wilt disease. However, these diseases are not necessarily fatal. 



Canker. — This stem disease, caused by the fungus Botryos- 

 phaeria iibis chromogena, has been seen on redbud in several 

 parts of Illinois. It causes cankers on branches (Fig. 80) and oc- 

 casionally on trunks of affected trees. The cankers are produced 

 during May and appear as inconspicuous, oval, flattened areas. 

 They become elongate and sunken as they enlarge during June. 

 Frequently cracks form between the living and dead bark. After 

 the cankers cease enlarging, callus tissues form along their mar- 

 gins and spread inward over the diseased areas. Small cankers 

 may be covered with callus tissues in a single growing season, 

 while large cankers may not be covered for several growing sea- 

 sons. Affected branches show sparse foliage, and branches gir- 

 dled by cankers die. 



In most cases, this disease can be controlled by removal of 

 the affected branches and by applications of plant food to stimu- 

 late vigorous growth of the affected trees, as described in the 

 section "Feeding." In severe cases, it may be necssary to re- 

 move the trees. 



Verticillium Wilt. — This vascular disease, caused by the fun- 

 gus VerticiUiiim albo-atrum, occasionally affects redbud and 

 causes partial to complete wilt of branches. Part or all of a wilt- 



Fig. 80. — Botryosphaeria cankers occur on branches and trunks of red- 

 bud in Illinois. This 2-yt'ar-old canker on redbud shows cracked and peel- 

 ing cankerous bark and callus tissue bordering the canker. 



