10 MAINE AGRICULTURAL EXPERIMENT STATION. 



recently been recognized in this country. It may have been 

 present for a much longer time before the characters which 

 differentiate it from similar troubles were recognized and 

 pointed out. In view of the experience of European growers 

 with this malady, and in view of the fact that Doctor Appel 

 says that what they call leaf-roll in Germany is identical with a 

 trouble which is associated with and apparently has become an 

 important factor in reducing the yields in certain central and 

 western states, notably in some of the irrigated sections of Col- 

 orado and Utah, it is important that Maine potato growers 

 become familiar with the characteristics of the disease and be 

 on their guard against it. 



After seeing field after field having plants affected in this 

 manner and seeing them in the presence of Doctor Appel, who 

 is probably the best authority on this subject, I am thorough- 

 ly convinced that there is such a thing as leaf-roll. I am also 

 just as thoroughly convinced that there are at least one or two 

 other types of foliage troubles which simulate this and grade 

 into it in appearance, and which at times it is impossible for 

 even the most expert to differentiate by simply looking at the 

 tops alone. This, however, has little real significance to the 

 practical man. He should look upon any abnormal type of 

 potato plant as something which should not be tolerated in his 

 field, and should not use for seed purposes tubers produced 

 by such plants. 



In this connection and at this point I wish to introduce for 

 the sake of emphasis, a general observation with regard to 

 tuber-borne potato diseases, and this includes nearly all the 

 more important potato troubles. The practical potato grower 

 does not need to be a trained pathologist in order to avoid 

 these difficulties. It is not even necessary for him to be able 

 to distinguish all of these various diseases, although it is often 

 an advantage to be able to do so. It does not take a very keen 

 observer to tell an abnormal or diseased potato plant or tuber 

 from a perfect one. If only sound, healthy and perfect pota- 

 toes, grown from healthy plants, are used for seed and then dis- 

 infected by one of the regular recognized means before plant- 

 ing, many of our potato troubles would vanish. For example, 

 powdery scab could have been kept out of Maine in this way 



