182 MASS. EXPEIUMEXT STATION BULLETIN 279 



yields resulted in the plots sprayed four times with Bordeaux mixture 4:4:50 or 

 three times with Bordeaux mixture 8:4:50. In onlj' one series of plots were de- 

 creased yields associated with these treatments. 



It is evident from this that >ields of onions may be increased somewhat by 

 Bordeaux mixture applied uniformly and at not too high a pressure, even in 

 years of no downy mildew and no blast. Such an effect is tentatively attributable 

 to a direct stimulation or to protection against fungi which are usually of minor 

 importance. Increases in yields were, however, too small on the whole to indi- 

 cate that spraying would be a profitable practice with neither blast nor downy 

 mildew present. 



Results in 1931 



There was no downy mildew in 1931, but blast was severe, appearing, as in 

 1927 and 1928, about the third week of July. 



It was evident by the first of August that onions sprayed with Bordeaux 

 mixture were blasting less and more slowly than were onions not so sprayed. 

 But the appearance of blast, although delayed, was not entirely prevented by 

 Bordeaux mixture, and the increases in yields following spraying with Bordeaux 

 mixture were not large. Yields were, however, increased somewhat in all plots 

 sprayed with Bordeaux mixture 4:4:50, and in all but one of the six plots sprayed 

 with Bordeaux mixture 8:4:50. 



Six applications of Bordeaux mixture 4:4:50 were followed by increases in 

 yields of from 2.4 to 41.2 per cent, but the increase in the mean yield of the three 

 plots (16.8 per cent) was no larger than that associated with the corresponding 

 treatment in 1930, when there was no blast. The most consistent and, on the 

 Avhole, the largest increases in yields (with a mean of 19.3 per cent) were in those 

 plots sprayed four times with Bordeaux mixture 4:4:50, but even in this case, 

 the increases in yields were not much more than those which followed a corre- 

 sponding treatment in 1930 with blast absent. 



Two applications of Bordeaux mixture 8:4:50 were of more benefit than 

 three applications of this fungicide, but increases in yield resulting from the 

 former were smaller in this year of blast than in the previous year when that 

 disease was absent. 



Our conclusion, on the basis of the results in 1931, is that increases in yields 

 resulting from spraying with Bordeaux mixture in a year of blast were not 

 sufficiently large and consistent to indicate that the practice would be profitable 

 under present conditions. 



Yields were increased 3.7 to 29.9 per cent in the plots sprayed with milk of 

 lime. These increases in yield in the presence of blast were, on the whole, larger 

 than in the two previous years when blast was absent; but increases were small 

 in two out of three plots. Milk of lime, on the whole, was of less benefit in both 

 1930 and 1931 than Bordeaux mixture, indicating that at least part of the benefit 

 of the Bordeaux mixture was probably due to its superior fungicidal properties. 



As in previous years, copper-lime dust was of no benefit. The onset of blast 

 was not m«>asurably retarded by it, and yields were lower in all plots to which 

 copper-lime dust was applied. The decreases in yields in dusted plots were larger 

 following five than following three applications. 



Discussion and Conclusions 



The absence of downy mildew in 1929, 1930, and 1931 made it impossible, 

 of course, to add to the knowledge concerning the efficacy and practicality of 



