February, '21] ever: leaf hopper control 69 



THE INFLUENCE OF LEAF HOPPER CONTROL ON POTATO 



YIELDS 



By J. R. Ever, State College, Pa. 



During the past two years comparative tests of different insecticide 

 and fungicide combinations have resulted in the conclusion that Bor- 

 deaux Mixture with excess lime or other materials to form a wash of 

 heavy consistency, with or without the addition of Nicotine Sulphate, 

 is most effective in preventing the phenomenon known as "Hopper 

 bum." 



In Wisconsin, Ball and Dudley obtained satisfactory results with 

 Bordeaux and Bordeaux-Nicotine sprays. In New York State, Parrott 

 and Olmstead have controlled hopper burn by Bordeaux-Lime washes, 

 although some foliage injury resulted from these heavy lime sprays. 



Dr. Ritzema Bos, experimenting in Holland, demonstrated the 

 reduction of potato foliage-burning by Bordeaux-Lime sprays, and also 

 noted an appreciable decrease, during cloudy seasons, in the tuber 

 production of sprayed plants. His experiments support the conclusion 

 that, during simny periods, the Bordeaux Mixture has a beneficial 

 effect on healthy plants due in a large part to the shading it produces. 

 During cloudy seasons, how^ever, this shading decreases the potato yield. 



This paper presents the details of two years experiments, conducted 

 under field conditions in Erie County, Pennsylvania. These tests were 

 made with especial reference to the control of hopper burn, and to the 

 effect of such sprays on tuber production. It is interesting to note that 

 there were but thirty-six sunshiny days in Erie County during the potato 

 growing season of 1919 and forty-five during the season of 1920. Accord- 

 ing to Professor Muncie, our Pathologist, late blight did not factor in the 

 results of the spraying experiments for either season. 



The experiments of 1919 indicated that Bordeaux Mixture produced 

 a fair control of hopper burn and increased the yield twenty-nine 

 bushels per acre. On the other hand, while Bordeaux-Nicotine sprays 

 decreased the percentage of hopper burn, these plots produced only one 

 bushel more potatoes per acre. Bordeaux-lime (4-8-50) controlled 

 hopper bum more effectively than either of the above sprays, but the 

 yield was twelve bushels below that produced by Standard Bordeaux 

 Mixture. 



On the basis of these results, more extensive experiments were out- 

 lined for 1 920. Comparisons were made using hand and power sprayers . 

 These tests clearly indicated that there was a difference in relative 

 control of hopper burn and in yield due to the method employed. These 

 factors are considered in discussing the efficiency of the several sprays. 

 Table I presents the data obtained from hand-sprayed plots treated with 



