MONTANA EXPERIMENT STATION. 141 



' DIPPING IN ARSENATE OF LEAD. 



At the writer's suggestion arsenate of lead, sccn-cl ironi tlie 

 ;^o\vker Insecticide Company, was used. This su'jsi'ance ]i;i.s cer- 

 tain marl-ced advantages over Paris green as g'.i arsenical insecticide 

 fo' nse on the foliage of plants. Being iTi;?.iliibic in v>'ater it may 

 ])e .-np-ied to tender leaves in much greatc.- strengrh than is safe 

 with Paris green. And there are very few insects, if any, that can- 

 U"! Ik killed by it or driven from the plants spra\"=id \\^i\\ i< . .More- 

 o\"cr, it remains on the foliage much more persistently than does 

 Pc.ris iTreen, and hence is very desirable in a climate with frequent 

 rams that would easily wash off an application of Paris green. . 



We suggested to ]\Irs. Williams that she try dipping her plants in 

 the substance before planting them in the field and then follow up 

 this treatment with later sprays as new foliage alppeared. It was 

 felt that if the beetles could be driven ofif from the new plan^-; the 

 bed would be free ever afterward. 



Mr. Jones watched this test and reported that dipped plants v/ere 

 entirely immune for al^out two weeks after setting an i after that 

 length of time the beetles gradually appeared and fed on the new 

 j;:owth that was being put forth. The foliage v/as then sprayed 

 and the plants were again immune, l)ut it was noticed that the plants 

 were not doing well and it was found that the ingenious beetles were 

 feeding on the roots ! It will be remembered that it is the habit 

 of these beetles to hide among the roots in the soft soil and it is not 

 surprising, that impelled by hunger, they fell to feeding on the roots. 

 Beside finding the roots of the plants gnawed, ]\Ir. Jones took the 

 troul:)le to make a microscopic examination of the contents of the 

 intestine and concluded that it was composed of what had been 

 eaten from the roots of the strawberry. The practical conclusion 

 drawn from this test is that, while the use of arsenate of lead in 

 the manner indicated cannot be relied upon to keep the bed free 

 from the l^eetle. the treatment is probably very much better than 

 nothing. Dipping the plants before setting them is easily done and 

 the cost and trouble of spraying two or three times with arsenate of 

 lead at the rate of five pounds to fifty gallons of water is not great. 



The one result of our investigations that appears to be of greatest 

 practical significance is the discovery of the fact that the trouble 

 Jrom the pest arises from the presence of great numbers oi the 



