70 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



Bordeaux-Lime and Bordeaux-Nicotine combinations. Table II pre- 

 sents siinilar data from machine-sprayed plots. 



As in 1919, Bordeaux 4-4-50 produced a normal increase in yield. 

 In hand sprayed plots 4-8-50 and 4-12-50 combinations produced 

 }'ields often lower than their respective checks, even though hopper 

 burn was decreased to four per cent. In machine-sprayed plots, each 

 of these combinations produced less tubers than Bordeaux 4-4-50. 

 Milk of Lime 8-50 controlled hopper burn fully as well as Bordeaux 

 4-8-50, but produced no increased yield. Kaolin added to Bordeaux 

 4-4-50 was not so effective as Bordeaux 4-8-50 in hopper bum control, 

 and decreased the weight of tubers to about the same extent as the latter. 



Other tests were made with Bordeaux-Lime-Nicotine and Nicotine- 

 vSoap combinations. Bordeaux-Nicotine spraj^s were quite effective 

 in controlling leaf hopper, and reduced hopper burn to three per cent 

 in hand-sprayed plots. On the other hand the yields were only slightly 

 above Bordeaux 4-4-50. Bordeaux 4-8-50-Nicotine was superior to 

 the 4-4-50-Nicotine combinations. Lime-Nicotine wash averaged less 

 than 4-4-50 Nicotine mixture in tuber production, and was not so 

 effective in control of hopper burn. Plots sprayed with Nicotine soap 

 solution produced almost as many tubers as plots sprayed with Bordeaux 

 4-4-50, but hopper burn was more in evidence. 



In all the tests Bordeaitx sprays with excess lime effectively controlled 

 hopper burn, but, as shown by Ritzema Bos, the shading effect of these 

 washes materially decreased the potato yield. In plots sprayed with 

 Bordeaux-Nicotine, the hopper burn was reduced to a minimum, but 

 in each case the yield was only slightly above standard Bordeaux. 

 In view of the fact that there is an added cost of -15.40 per acre in Nico- 

 tine sprays, with a corresponding average gain of but six bushels more 

 per acre than with standard Bordeaux, is it not logical to question the 

 economy of attempting the control of hopper burn in regions where 

 there is comparatively little sunshine during the growing season? 



Table I. — Hand Sprayed Plots 



Kind of Amoun t of Tipburn Yield per Acre Average 



Materials Potatoes Treated Check Treated Check Increase 



Dercent percent bu bu. oer Acre 



Bordeaux Mixture 4-4-50 Early 12 25 142 136 6 



Late 28 60 126 122 4 



Bordeaux Mixture 4-8-50 Early 10 25 144 148 -4 



Late 10 60 122 122 



Bordeaux Mixture 4-12-50 Early 4 25 137 150 -13 



Milk of Lime S-.50 Late 34 70 90 89 1 



Bordeaux Mixture 4-4-50 and Early 10 25 156 150 6 



Nicotine 1-800 Late 7 60 108 89 19 



Bordeaux Mixture 4-8-50 and 



Nicotine 1-800 Late 3 60 134 122 12 



Milk of Lime 8-50 and Nicotine 



1-800 Late 24 60 124 122 2 



Nicotine and Soap Early 13 25 148 143 5 



Late 50 60 126 122 4 



