MAN'S CONQUEST OF NATURI<: 



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part of the United States, they have almost been exterminated. 

 Even more serious is the more recent introduction of the Dutch elm 

 tree disease, a wilt that was introduced in an importation of European 

 elm logs shortly before 1930. At that time, this disease had been 

 found in several localities extending as far west as Indiana and Ohio 

 and as far south as Norfolk, Virginia, marking places where the 

 infected logs had been shipped. It attacks the wood and is spread by 

 the European bark beetle as well as by other means. A determined 

 campaign is now being waged to stamp out this disease, which, unless 

 controlled, will doom our native elms to destruction as it has those of 







USUAL inular \o -jJJ 



Dutch elm disease. Brood galleries of Scolylus muUisfriatus, an imported beetle. 



Europe in the past fifteen years. The latest estimate by Charles 

 Lathrop Pack calls for the destruction of 25,000,000 trees in order to 

 save the remaining elms on this continent. In view of a program of 

 this magnitude it would seem impossible to save our elms, because of 

 the difficulty in completely eliminating the fungus. 



The most important class of the fungi from the economic viewpoint 

 are the Basidiomycetes, fungi that bear asexual spores on a charac- 

 teristic structure called a hasidium. Among the worst pests of this 

 kind are the corn smut, which causes the commonly seen smut balls 

 in ears of corn, many different grain smuts, grain rusts, and one white 

 pine blister rust, besides many fungus diseases of wood. In this 

 class are also found the mushrooms, both edible and poisonous. 



If we add to the above list the poisonous plants of this country, such 

 as loco-weed, jimson weed, poison ivy, poison oak, and poison sumac, we 

 have a formidable list of plants contending with man for supremacy. 



