EXPERIMENT STATION BULLETINS. 



665 



Bordeaux mixture does not kill the leafhopper but merely acts as 

 a repellaut. Vines covered with bordeaux mixture are not relished by 

 the leafhopper and the insect flies to other hosts or to other potato fiebK- 

 which have not been sprayed. 



DUSTING EXPERIMENTS 



Preliminary experiments with various dusts were conducted during 

 the 1921 season to ascertain what effect they had on hopperburn and leaf- 

 hopper control. 



A dehydrated copper sulphate and lime dust was applied with a 

 hand dusting machine to two rows of potatoes in the spray plot at the 

 Upper Peninsula Station. Four applications were made during the 

 season. On September 9, the dusted rows showed conspicuously more 

 vigorous vine growth than the checks which had had no treatment. 

 (Fig. 13). The foliage of the dusted rows was deep green in color wdiile 

 that of the check rows had a decided brownish cast due to hopperburn. 

 The dusted rows also compared very favorably with those which were 

 sprayed with bordeaux mixture. 



Fig. 13. 1921 dust plot. Dchyi" rated copper sulnliate and lime dust kent the vines green and in vigoroas growing condition 



Photo taken Sept. 9 1921. 



In addition to the above experiments, trials were made with dusts 

 impregnated with nicotine to determine effects upon the leafhopper. 

 Black leaf 40 was used as source of nicotine. Dusts were made con- 

 taining two and three per cent of this product, w^hich interpreted in 

 terms of nicotine would be .8 and 1.2 per cent respectively. The dusts 

 were applied by means of a hand dusting machine. Six hills were dusted 

 at each trial, and the insects which dropped from the vines were col- 

 lected on sheets of wrapping paper which were spread underneath the 



