752 ANNUAL, REPORT OF THE Off. Doc. 



iLe Colorado iioLaLu-beetles. A strong force pump is beet, as then 

 every part of the foliage can be covered by the liijuid. During the 

 operation of spraying the liquid should be frequently stirred, other- 

 wise the ingredients will not be evenly distributed through the mix- 

 ture." 



Having given the Cornell suggestions, based upon success that 

 must be rated as unusually high, I cannot serve the grower better 

 than to couple with it the suggestions of Prof, W. J. Green, of the 

 Ohio Station, who has given potato culture many years of scientific 

 study. In Bulletin No. 76 he says: 



'^'It has been our custom to make four or five applications of Bor- 

 deaux mixture to the ])otato tops each season, including Paris green, 

 to destroy the 'bugs.' In some cases this course has been satisfac- 

 tory, but the results have been variable. Some seasons the 

 sprayed plants have remained alive two w^eeks longer tihan the 

 uusprayed, and the yield was considerably increased by the treat- 

 ment, but at other times the spraying was of no apparent 

 benefit. Our experience has been duplicated by many others, and 

 spraying for the potato blight is practiced less than formerly. Pro- 

 fessor A. D. Selby, Botanist of the Station, suggests that the discrep- 

 ancies in results may be due to a confusion of ideas regarding the 

 cause of potato blight. Some have confounded tip burn of the 

 leaves, in dry hot weather, with blight. Others have mistaken the 

 effect of drought for blight. It is probable, also, that a bacterial dis- 

 ease, not amenable to fungicides, has been the cause of much of the 

 trouble. 



''Where fungi alone are responsible for the dying of the potato tops, 

 repeated experiments have shown that sraying with Bordeaux mix- 

 ture is beneficial. Where the bacterial disease prevails it appears 

 that insects are largely responsible for its spread, also that the 

 malady maj' be carried into the field in diseased tubers. In this 

 case prevention consists in using sound seed and in keeping the in- 

 sects in check. 



"The work of the experimenters does not appear to be finished, 

 either along the lines of investigations concerning the causes of 

 blight, or in the discovery of the best means of preventing it, but it 

 is not wise for potato growers to give up trying to combat it. They 

 could deal with it more intelligently and successfully if they knew 

 whether to spray for fungi in the form of the 'early blight' or the 

 'late blight' or whether to be on their guard against a bacterial 

 disease. 



"Meanwhile the only safe plan is to guard all sides. If potatoes 

 rot in the field before digging, and continue to rot in the cellar, 

 the disease will most likely be transmitted to the succeeding crop. 

 If they appear to be sound on the outside but when cut aorosa the 



