66 VERMONT AGRICULTURAL REPORT. 



II. ADDITIONS OF BUG DEATH AND PARIS GREEN TO BORDEAUX 



MIXTURE. 



This experiment was conducted in a field belonging to the Mary 

 Fletcher Hospital. Its object was to determine the relative efficiencies 

 of bug death and paris green when used alone and with bordeaux mix- 

 ture in the latter part of the season. 



The plots were dug on October 7th (two months after spraying), when 

 the tops on all the rows were entirely dead, with an occasional exception 

 where bordeaux mixture had been used. The following gives the treat- 

 ment and the yield from each treatment (three rows), in pounds: 



Treatment. Yield, 3 rows. 



Paris green 220 pounds. 



Control (untreated) 241 pounds. 



Bordeaux-paris green mixture 278 pounds. 



Bordeaux-bug death mixture 280 pounds. 



Bug death applied dry 237 pounds. 



The conclusions warranted by the results thus far discussed seem to 

 be as follows: 



(1) Neither paris green nor bug death used alone have value in 

 checking the late blight, even where, in the case of bug death, very lib- 

 eral application is made. 



(2) So far as controlling late blight is concerned, bordeaux-bug 

 death mixture and bordeaux-paris green mixture are both efficacious, 

 the one as good as the other, and doubtless simple bordeaux mixture 

 without any insecticide added would prove as good as either. 



To avoid being misunderstood, we will repeat what we have stated in 

 previous years, that it is outside of the plans of these experiments to 

 inquire closely into the insecticidal value of bug death. We have, how- 

 ever, seen evidence that it has such value in trials of former years. 

 This year in the absence of insects this factor did not enter into the 

 results. 



III. RELATION OF DATE OF DIGGING TO DEVELOPMENT OF ROT. 



"How soon after the tops begin to die from the late blight should the 

 potatoes be dug?" This question is of much practical importance and we 

 undertook in 1902 to secure an answer. Although the results obtained 

 in those trials appeared definite and justified a tentative deduction, it was 

 felt that conditions might so vary from year to year that further trials 

 were needed. Accordingly on August 31, twenty rows of potatoes, 

 forty-five feet long, were staked off on a field belonging to the Mary 

 Fletcher Hospital. These were on rather low ground in slightly moist 

 and somewhat sandy soil. The late blight was abundant over the entire 

 field, although it had mostly developed within the preceding week. On 

 the plot selected one-third to one-half of the foliage had been killed 

 during this week by late blight. 



Four rows were dug on each of five different dates, at intervals of 

 one week, in such a manner as to give each time as near as possible an 

 average of the plot. 



