SUPPRESSION OF INSECT PESTS AND PLANT DISEASES. 



the widely divergent interests of the different States, the lack of anything like 

 cooperation, and the fact that public sentiment in many cases is indifferent or unfa- 

 vorable toward such laws, thus making proper enforcement impracticable. 



I take it that one of the principal objects of this convention is to consider these 

 matters, and, after hearing as many sides to the question as possible, to take some 

 action which will at least lead to a better understanding of what can or can not be 

 done. Let us, then, consider for a moment the nature of some of the more common 

 and destructive plant diseases, for it is only in the possession of such knowledge that 

 we can intelligently discuss the problems relating to legislation. 



So far as we are at present concerned, the diseases of plants may be divided into 

 two principal groups, namely, those due to organized beings, such as insects and 

 fungi, and those in which organisms take no direct part, as, for example, improper 

 conditions of the soil, such as too much or too little water; unfavorable atmospheric 

 influences; and the presence of poisonous substances in the soil, air, etc. In this 

 paper we are not particularly concerned with the insect pests, as they will doubtless 

 receive full consideration from others present. 



No hard and fast lines can be drawn between the diseases due to fungi and those 

 brought on by unfavorable environment. Many, if not all, fungous diseases are 

 greatly influenced by environment just as much so as the hosts themselves. In 

 many cases we find that a plant grown with success in a certain region succumbs to 

 disease when transferred to another where the conditions are such as to make it nec- 

 essary for the plant to adapt itself to the new requirements. During the process of 

 adaptation fungi may find opportunity, and the host once infected it may be only a 

 question of time when it is forced to succumb. In such cases it would be obviously 

 unjust to hold the man who grew the trees responsible. It was not his fault that 

 the conditions under which the purchaser planted the trees were different from those 

 nature furnished him to grow them. 



A case in point will more clearly illustrate this matter. Suppose I purchase a thou- 

 sand apple trees from a nurseryman and plant them in what to all intents and pur- 

 poses is a suitable piece of ground. This ground may have recently been cleared, 

 and in addition to the remains of roots of certain forest trees, the soil may be slightly 

 wetter than that of the nursery. The decaying roots of the forest trees in the soil 

 may contain the mycelium of a fungus, which under ordinary conditions would not 

 attack a healthy apple root. Owing to the slight additional wetness, however, and 

 the consequent lack of aeration, some of the apple roots in time will be asphyxiated, 

 or will be injured in other ways, the details of which need not be given here. While 

 the roots may be only slightly injured, they nevertheless in this condition become 

 readily susceptible to the attacks of the fungus already in the soil, and the disease 

 once started all the roots may eventually be killed, and the tree will die. Hundreds 

 of trees may be killed in this or some similar way, and yet from the very nature of 

 the trouble, the delicate questions involved, and the complications that may arise, 

 no man could positively assert where the blame rests. 



We are by no means holding the nurseryman up as a paragon of honesty, but we 

 do wish to give him fair play, for he is unquestionably often blamed for things for 

 which he is not in the least responsible. 



Again, there is a vast number of fungous diseases which are almost as universally 

 distributed as the host plants themselves. They occur not only on the cultivated 

 forms, but in the woods and wild places, whence they doubtless originally came. 

 Such is black rot, downy mildew, and powdery mildew of the grape; apple scab 

 and rust; and a host of other maladies. It would be manifestly as impossible to 

 control such enemies by legislation as it would be to control the dust of the air or 

 the wind that wafts it from place to place. Furthermore, it must be remembered 

 that a great many in fact the majority of the most destructive diseases which affect 

 nursery stock are of such a nature that no reliable system of inspection can be car- 

 ried out. Such being the case, we are free to say that in most cases the certificates 

 that are given declaring trees to be free from disease are little better than worthless. 



