DUTCH ELM DISEASE IN ILLINOIS 



11 



Fig. 9. — Magnified 

 view of fungus tliat 

 causes Dutch elm disease. 

 These colorless, oval 

 spores, produced on short 

 fungus strands, are not 

 visible to the naked eye. 



Fig. 10.— The Dutch elm dis- 

 ease fungus is introduced into 

 healthy elms through bark bee- 

 tle feeding wounds made in the 

 crotches of 1- and 2-year-old 

 shoots. These wounds extend to 

 the sapwood beneath the bark. 



Fig. 11.— The smaller 

 European elm bark bee- 

 tles make numerous small 

 holes in the bark as they 

 emerge. The holes resem- 

 ble those made by small 

 buckshot. 



