282 



TWENTY-PIRST REl'ORT. 



25% of the hills so affet'ied. In the latter part of the season the diseased 

 plauts showed a slight yellowing and an upturning of the leaves along the 

 midrib. In some cases the yellowing was absent. There appeared in some 

 fields the rosette effect and in others the aerial tubers. Stem lesions were 

 quite generally evident. A field of Russet Rurals on stump ground showed 

 r>0% of the hills having the upturned leaves. 



The summary of my observations given in the lahlo below shows that 

 oidy about 4% of the diseased fields had over 1% injury. It is (bus evident 

 that the disease under soil conditions was not doing any considerable amount 

 of daujage to the crop as a whole, but in certain fields the loss might be 

 severe. 



SUMMARY TABLE No. 11 



ARSENICAL INJURY. 



The injury caused by this trouble was not evident in sufficient amounts 

 to affect the crop to any appreciable extent. In some cases it was diflicult to 

 determine just whether the discoloration and dying of the leaf extremity was 

 due to arsenical injury or to tip burn. Sixty-seven per cent of the fields visited 

 showed the trouble in amounts ranging from a trace to 10%. Only 18% of 

 the affected fields showed the injury in amounts over a trace. Seventy-three 

 per cent of the counties visited showed all the fields to be clean. 



BLACK LEG (BACILLUS ATROSEPTICUS. ) 



This disease was found in 27% of the fields visited, being nuich less abun- 

 dant in the southern part of the state than elsewhere. This distribution of 

 the disease was very likely due to the fact that the pathogene has not yet 

 been inroduced into the southern part of the state. In many counties the 

 farmers are beginning to realize the need of planting disease-free seed. Re- 

 moval of the affected hills is being practiced quite generally. In some of the 

 diseased plants the bacteria had proceeded along the stolon to the small new 

 tubers, there forming a pocket of bacteria slime in the stem end. 



In connection with the summary given in the table below, it is interesting 

 to know tliiit llio average percciifage of injury for the entire number of dis- 

 eased lields was 1.8%. Since this di.sea.se prevents the f(U"ma(i(>n of any 

 marketable potatoes (tii the affected plant, the above percentage may well be 

 taken as representing the loss to the farmer: 



