30 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



the elm bark beetle that carries the Dutch elm disease fungus 

 and the elm leafhopper that carries the phloem necrosis virus. 



Minerals may be sprayed on foliage of trees to correct some 

 nutritional deficiencies. Chlorosis resulting from an iron defi- 

 ciency can be corrected temporarily by spraying the foliage with 

 a solution of ferrous sulfate or other suitable iron compound. 

 This type of treatment is effective only on the foliage sprayed 

 and only for a single growing season. Most lasting control is 

 obtained by treating the soil to correct the deficiency. 



Improper spraying, the use of the wrong material, or spray- 

 ing at the wrong time may result in plant injury. Spray injury 

 may occur as discolored, distorted, or burned leaves, defoliation, 

 killing of twigs and branches, or stunting of growth. Spray drift 

 or vapors from herbicides such as 2,4-D and 2,4,5-T frequently 

 cause injury to trees as well as other plants. 



Surgery 



Some types of tree injuries and diseases may be corrected 

 or overcome by surgery. Limited bark injuries caused by rodents, 

 humans, machinery, and other objects can be overcome by remov- 

 ing the damaged bark, tracing (cutting) the margins back to the 

 uninjured bark, and then coating the exposed wood with tree 

 wound paint or shading the wounded part. Shading the wound 

 area within a few hours after the damage has occurred, and be- 

 fore the injured tissues are exposed to the sun, prevents drying 

 and death of the living cambial cells that remain on the surface 

 of the exposed wood and encourages the entire surface to callus 

 over rapidly. Extensive injuries with destruction of the cambium 

 and girdling damage by rodents may be overcome by bridge 

 grafting. 



Canker diseases that attack trunk bark and wood, such as 

 fire blight and target canker, may be controlled by surgery. In 

 removing the diseased tissues and disinfecting and painting the 

 exposed wood, exercise care to prevent spreading the disease 

 organism to other parts of the tree or to other trees. An effective 

 disinfectant is denatured alcohol. 



Cavif-y Treatment 



You can prevent wood decay which produces cavities in 

 trunks and branches by properly treating freshly made wounds 

 as described in the surgery section above. 



Wood rot diseases, once established, are very difficult if not 



