202 Minnesota Plant Diseases. 



officials of the United States department of agriculture, which 

 placed the loss in the whole United States in 1882 on all agri- 

 cultural products due to insects' ravages at 200 to 300 millions 

 of dollars. 



No estimates are readily available for losses on smaller epi- 

 demics nor on local ravages of fungus pests where conditions 

 have favored a restricted epidemic. It is well known, how- 

 ever, that the potato disease in certain wet seasons causes enor- 

 mous losses, particularly in eastern states and in Europe. In 

 the few years following its introduction in about 1845 the losses 

 amounted in many places to a complete destruction of the po- 

 tato crop. Garden truck and orchards yearly suffer in almost 

 all sections of the country. In many cases the losses are not 

 deemed important, but though slight, amount to great sums in 

 the aggregate. We hear of rust-free seasons for grains but no 

 year is absolutely free and such small unnoticed loss has come 

 to be accepted as an inevitable tax upon grain. It is against 

 such losses as well as against the great loss by epidemics- that 

 attention will have to be directed. It must be clear from the 

 above figures that the fight against fungus diseases is not a 

 mere illusion entertained by a few enthusiastic specialists but is 

 a most important and vital economic feature of all future 

 branches of plant industries. 



Prevention and cure. If there is one thing which will con- 

 tribute more than any other to the relief of agriculturalists and 

 horticulturalists from the losses incurred by the disease of 

 plants it is knowledge. No one would hesitate to affirm that 

 more extensive knowledge of the real nature of the diseases of 

 man has lessened enormously the destructive attacks of those 

 diseases. The force of this analogy is comprehended by few in 

 its application to plant diseases. The practical plant grower 

 wants to know only the cures, — sprays or whatever they may 

 be, — he often does not care to study or learn the details of the 

 disease-cause and its mode of action. But it is only with this 

 knowledge that an intelligent application of remedial measures 

 is possible. Probably no two occurrences of a plant disease 

 have exactly similar conditions. The generalities which under- 

 lie them are to be found only in a knowledge of the action of 

 the disease-causing organism. The details of treatment must 



