REPORT OF THE SECRETARY. 57 



Potato wart, a new disease that is likely to prove very destructive 

 if introduced into this country, has been causing alarm in Europe. 

 Canada, Ireland, and other countries are quarantining against it, but 

 the United States has no protection. It has already appeared in 

 Newfoundland and has been brought once to ^lassachusetts. Several 

 other diseases now in foreign countries may be introduced at any 

 time. The experience with the chestnut blight illustrates the devas- 

 tation that may ensue. This may even yet be repeated on a larger 

 scale than with the white-pine blister rust unless Congress authorizes 

 the Secretary of Agriculture to prohibit the entry of diseased plants 

 and seeds. 



WORK ox SUGAR-BEET IMPROVEMENT. 



A campaign is being carried on to increase the average yield per 

 acre of sugar beets. The tonnage produced in the United States is 

 still Jower than it should be. Some sections do not appreciate the 

 need for thorough culture; others have attempted to grow beets con- 

 tinuously, and need to adopt rational systems of crop rotation. All 

 need to maintain the fertiUty of the soil and to make beet growing 

 a part of the system of permanent agriculture. Diseases are the 

 underh^ing causes of low tonnage in some districts, and there the 

 Department is concentrating its efforts to determine the best means 

 of relief. 



The improvement of American beet seed is being given much 

 attention, and there are indications that the quantity grown in this 

 country will increase greatly in the near future. 



SOIL-BACTERIOLOGY AND WATER-PURIFICATION INVESTIGATIONS. 



The results reported by cooperators using cultures of nodule- 

 forming bacteria for inoculating legumes have indicated certain limi- 

 tations to successful inoculation. Especially with alfalfa in the 

 Coastal Plain region it has been found that inoculation is generally 

 successful upon soils which produce a blue or neutral reaction to 

 litmus paper, while upon those soils giving a red reaction to neutral 

 litmus paper successful inoculation is seldom obtained. Extensive 

 studies upon the nitrifying power of soils have been carried on in 

 different parts of the United States, and a close relationship has been 

 established between the nitrifying power of a soil and its crop-produc- 

 ing power. In none of the regions under investigation has any 

 injurious effect from overnitrification been observed. 



PROGRESS IN ACCLIMATIZATION AND ADAPTATION OF CROP PLANTS. 



Acclimatization of new varieties of cotton. — There are many 

 desirable varieties of cotton, corn, and other economic species in the 

 tropical countries where these plants had their origin and were first 



