52 



] THE PARASITIC ENEMIES OF CULTIVATED PLANTS.* 



Bt B. T. Galloway. 



Of the United States Department of Agriculture. 



A study of nature leads us to believe that since the very dawn of 

 life on the earth a constant warfare has been going on between living 

 beings of every kind. Out of this carnage and strife have arisen the 

 almost endless forms of life we see about us on every side at the present 

 day. The struggle is not by any means ended, nor is it being fought 

 to-day on any radically different lines from what it was in the ages 

 gone by. Plants growing iu our meadows, woods, and pastures at the 

 present time are beinij destroyed by innumerable animal and vegetable 

 foes, wbile these in turn are disappearing before the relentless attacks 

 of their enemies much as they did in the days of the ancients. That 

 man plays an important part in this struggle, and that the outcome in 

 many cases deeply concerns him, goes without saying. It is often a 

 question of vital importance to him whether he can turn the battle in 

 his favour, or, if he is the intended victim, whether he can find a means 

 of coping successfully with his enemy. 



It is of these questions we propose to speak, in the hope that what 

 is said will lead to a better understanding of what science is doing for 

 agriculture, horticulture, and kindred industries upon which so much 

 of the nation's wealth and prosperity depends. 



This brings us properly to the subject of this paper, i.e., the modern 

 methods adopted by man in fighting the enemies of cultivated plants. 

 Before taking up the question directly, however, it would perhaps be 

 well to say something about the enemies of plants themselves, as a 

 knowledge of what the/ are and in what manner they destroy our crops 

 will make what is said about fighting them more intelligible. It 

 would be entirely beyond the province of this paper to discuss all the 

 enemies of plants or, for that matter, even a very small number of them. 

 Our remarks, therefore, will be confined to two kinds of enemies which 

 cause diseases in plants ; but first it is important to get a clear know- 

 edge of what constitutes a disease, after which it will be proper to 

 consider the causes that may bring about such conditions. Taking up 

 the first question we will say that any derangement of the vital functions 

 of an organism, whether it be animal or plant, may be characterized 

 ^8 a disease. 



Under this definition, which is rather a broad one we will admit, 

 the plant may be diseased and btill serve its purpose so far as its useful- 

 ness to man is concerned. Perhaps the best definition of the word for 

 us to adopt, as we are not addressing our remarks to scientists, is that a 

 disease is any change in the normal condition of a plant which results 

 in a failure or partial failure to produce the usual quantity or quality of 

 grain, fruit, foliage, flowers, or whatever the part used by or for man 

 may be. Now, then, accepting the foregoing definition, let us consider 

 for a moment some of the causes which may bring about the conditions 



* From Cbautauquan, 



