62 MASS. EXPERIMENT STATION BULLETIN 189. 



Application of Arsenicals to Plants. 



Although much of the literature dealing with the habits of the European 

 corn borer emphasizes the fact that the larva feeds entirely within the 

 plant, close observation of the habits of the insect has shown that a large 

 proportion of the first and second instar larvae feed almost exclusively on 

 the upper and lower leaf epidermis of some of their host plants. This 

 circumstance at once suggests the possibility of control by the application 

 of arsenical poisons, and experiments were attempted during the summer 

 of 1918 in order to determine this point. 



Dusting with Lead Arsenate. 

 An application of powdered lead arsenate was made on June 24, 1918, 

 to 60 hills of sweet corn growing in the ex^ierimental plot at West Med- 

 ford, Mass. At this time most of the corn borer larvse were feeding on 

 the leaf epidermis or on the staminate flowers of the tassel. An attempt 

 was made to get the poison into the unfolding tassel and around the 

 bases of the corn blades, as well as to cover the surface of the leaf blades. 

 This treatment did not noticeably curtail the activities of the larvse. 

 When the ears developed they were infested in the same proportion as 

 the check rows. 



Other Dusting Experiments. 

 Calcium arsenate powder and equal parts of calcium arsenate powder 

 and hydrated lime were applied in the same manner as arsenate of lead. 

 The results were the same, although calcium arsenate appeared to be 

 more effective than any of the other arsenical powders used. The check 

 rows used in the calcium arsenate experiment were noticeably infested to 

 a greater degree than the treated row. All the ears in the treated row 

 were at least somewhat infested, however. 



Spraying with Lead Arsenate. 



Three applications of lead arsenate, at the rate of 1 ounce of the powder 

 in 2 gallons of water, were made to 32 hills of sweet corn on Aug. 5, 13 

 and 22, 1918. Daily observations were made of these corn plants, and 

 an effort was made to apply the poison at a time when it would be most 

 effective in covering the surface areas of the plant that was being eaten 

 by the larvse of the borer. 



At the time of apphcation the poison spray adhered to the foliage very 

 well, and the excess liquid ran down the leaf blades and collected at the 

 bases of the tassels and leaf blades, these points being the favorite feeding 

 places of the young larvse. 



When the ears developed in this plot a close examination showed that 

 211 ears were present, of which the entire number were infested. Many 



