CARTER: ILLINOIS TREES: THEIR DISEASES 



37 



Fig. 37 (left). — The exposed wood is disinfected with denatured alcohol 

 and painted with a wound dressing. 



Fig. 38 (right). — Wounds may need to be repainted once or twice each 

 year with a wound dressing to prevent wood rot fungi from attacking the 

 exposed wood. This picture shows fruiting bodies of the wood-rotting 

 sulfur fungus growing on exposed wood of a wound which has been treated 

 with only one application of a wound dressing. 



Christine Buisman and the Bea Schwarz seedling selections of 

 elm are resistant but not immune to Dutch elm disease. Diseases 

 for which resistant varieties or selections of trees are being 

 tested include oak wilt, elm phloem necrosis, white pine blister 

 rust, mimosa wilt, and poplar cankers. 



ARBOR-VITAE 



Arbor-vitae or white cedar trees are relatively free from 

 parasitic diseases but are affected occasionally by winter drying. 



Winter Drying. — This trouble, also called winter injury, 

 frequently appears in late winter or early spring. It develops as 

 extensive browning and death of foliage on 1-year-old or older 

 shoot growth. Often it kills branches and, occasionally, entire 

 trees. Winter drying frequently appears after periods of rapid 

 changes in temperature, especially when a rapid rise in tempera- 



