SPRAYING AND DUSTING ONIONS 179 



coverage. This represented a cost of $1.05 per acre for each apphcation. 



The most expensive item in each combination was the nicotine sulfate which 

 added approximately $2.50 per acre to the cost of each application. Since Bor- 

 deaux or lime alone, however, proved no fleterrent for thrips, the addition of 

 nicotine sulfate was necessarv. 



Results in 1929 



The season of 1929 was very dry. Some drouth injury occurred, hut neither 

 Mast nor downy mildew was observed in this season. 



Eight applications of copper-lime dust applied at weekly intervals, i)egiiming 

 July 1, resulted in decreases in yields of from 23.6 to 30.2 per cent. \'ields were 

 decreased rather more by six applications of copper-lime dust applied weekly, 

 beginning July 22. In the absence of disease and vmder the weather conditions 

 prevailing in 1929, copper-lime dust as applied was injurious to onions. 



Leaves were rather severely injured by Bordeaux mixture 4:4:50 and by 

 Bordeaux mixture 8:4:50 applied twice by hand, as described above. Milk of 

 lime similarly applied was not markedly injurious. This injury is attributed 

 more to the over-spraying and uneven coverage than to Bordeaux mixture itself; 

 for in the case of early applications and applications in the two following years, 

 made at a pressure of 100 to 150 pounfls with the field sprayer (3), no injury 

 by Bordeaux mixture was observed. 



With no disease present and with spray injury- apparent, it is not surprising 

 to note (see Table 1) that decreased yields resulted in all plots sprayed with 

 Bordeaux mixture. Bordeaux mixture 4:4:50 applied eight times at intervals of 

 two weeks, beginning July 1, or Bordeaux mixture 8:4:50 applied 5 times at 

 intervals of two weeks, were most injurious, resulting in reductions in yield of 

 from 26.0 to 34.7 per cent. The injury following six applications of Bordeaux 

 mixture 4:4:50, made at weekly intervals, beginning July 22, was much less: the 

 reductions in yields in this case were from 1.6 to 11.9 per cent. 



In two plots sprayed with milk of lime, there were small increases (7.4 per 

 cent) in yield, but in the third plot thus treated, a decrease in yield resulted. 



It is evident from this that Bordeaux mixture applied by hand and at too 

 high a pressure, injured onions, and that this injury, with diseases absent, more 

 than offset any possible beneficial effect of spraying. 



Results in 1930 



Yields (see Table 2) were low in 1930, although in 1930 as in 1929, neither 

 blast nor downy mildew was present. 



Yields were neither increased nor decreased consistently and significantly by 

 copper-lime dust applied four times or six times at weekly intervals. 



Six applications of milk of Ume at weekly intervals resulted in decreases in 

 yields of 4,9 and 10,2 per cent in two plots and an increase of 3,9 per cent in the 

 other plot. The mean yield in plots sprayed with milk of lime was decreased by 

 3.9 per cent. 



The effect of Bordeaux mixture, while not imiform in all plots, was in general 

 beneficial. Increases in mean yields resulted in all cases, with the largest increase, 

 19.5 per cent, in the plots sprayed six times with Bordeaux mixture 4:4:50 or 

 twice with Bordeaux mixture 8:4:50. Smaller increases (14.3 per cent) in mean 



