102 REPorRT OF THE BoTANICAL DEPARTMENT OF THE 
As in previous years, the difference in yield between Series I 
and II was greater than would be expected, judging from the 
difference in the appearance of the foliage. Only at the close of 
the season was there any apparent difference between the rows 
Sprayed three times and those sprayed five times. The three- 
sprayed rows were so little injured by blight that the average 
observer would not have noticed it except by comparison with 
the adjacent five-sprayed rows. Yet the difference in yield was 
at the rate of 42 bu. per acre. 
Loss from rot.—There was a little rot on both sprayed and 
unsprayed rows. It was impossible to estimate the amount 
accurately because many of the affected tubers were in an 
advanced stage of decay. Although there seems to have beeu 
somewhat more rot on the unsprayed rows than on the sprayed 
the casual observer might have thought the reverse true for the 
reason that on the unsprayed rows many affected tubers had 
decayed almost completely and nearly disappeared, while on the 
Sprayed rows the decay was less advanced and all of the affected 
tubers still in evidence.*? The very large yield on the sprayed 
rows is evidence that there was not much loss from rot on those 
rows. ‘The difference in yield between sprayed and unsprayed 
rows was due chietly to the longer growth of the sprayed plants 
and only in small degree to the prevention of rot. 
13At digging time all tubers showing the least indication of rot were 
carefully sorted out. Nevertheless, after three months in storage there 
was a considerable amount of rot among the sprayed tubers but none among 
the unsprayed. On three rows the amount of this rot was determined and 
found to be as follows: 
Row §&, sprayed 5 times, 380% pounds rotten 25 bushels 12 pounds per 
acre. : 
Row 9, unsprayed, none rotten. 
Row 10, sprayed three times, 4014, pounds rotten = 34 bushels 12 pounds per 
acre. 
This does not mean that spraying causes potatoes to rot in storage. 
Usually, sprayed potatoes keep better than unsprayed ones. Our explanation 
of the matter is that the sprayed potatoes were dug too soon after the tops 
died. 
At the time of digging, the unsprayed rows were long since dead and 
about done rotting while the sprayed rows were not. Hence, it was less 
easy to detect the rotten tubers on the sprayed rows and some slightly 
affected ones were accidently passed as marketable. It is also likely that 
in digging, the tubers on the sprayed rows were brought into contact with 
live blight spores on the foliage and infected in that way. Had the digging 
been delayed a few days these spores would have died when the tops became 
dry and the tubers could then have been dug with safety. If blighted potatoes 
are to be stored they should not be dug until the tops are thoroughly dry. 
(See page 192.) 
