DUSTING AND SPRAYING EXPERIMENTS OF 1918 AND 1919. 47 



EXPERIMENTS WITH POTATOES 



DUSTING POTATOES TO CONTROL THE 'COLORADO POTATO BEETLE 



In 1918 on the Horticultural grounds at East Lansing a comparison 

 was made of the dusting and spraying methods of application of poison 

 for the control of the Colorado potato beetle or "potato bugs" as they 

 are commonly called. A small field of about fifty rows was used for 

 this work. 



Materials. The field was divided into two plots of about equal size. 

 They were treated with materials as follows: 



Plot 1. Dusted. An 85-15 mixture of calcium arsenate and talc was 

 used. The talc was simply a filler or diluent. This mixture 

 was very fine, smooth and easy-flowing. 



Plot 2. Sprayed! Calcium arsenate at the rate of iVs Ibs. in 50 gal- 

 lons of water. 



Application. The dusting was clone with a power orchard duster and 

 with the regular orchard outlet which is simply a galvanized iron pipe 

 four inches in diameter. Four rows were dusted at each trip through 

 the field. The outlet was held rather close to the ground and swung 

 from side to side. The plants w r ere covered satisfactorily in this way. 



The spraying was done with an attachment with two nozzles for each 

 row. 



RESULTS 



As soon as the dusting and spraying were finished a number of plants 

 in each plot were marked for observation. Plants were selected for 

 this purpose that had a considerable number of adult beetles or larvae 

 on them. There were, however, only a few adult beetles found at that 

 time, most of the insects being in the larval form. 



Both methods of application w r ere entirely successful. Within two 

 hours after the application of the dusting material, the larvae were 

 showing effects of the poison. No live larvae could be found the next 

 morning (eighteen hours after application) on either plot. 



