52 BULLETIN 322 



Ar senate of lead 



From success obtained with arsenate of lead in controlling the closely 

 allied cigar case-bearer and pistol case-bearer on apples, it has been sug- 

 gested that the larch case-bearer could be controlled by the same method. 

 It must be remembered, however, that the pistol case-bearer, at least, 

 eats much larger quantities of the foliage. That is, it is not so exclusively 

 a miner as is the larch case-bearer. Moreover, the cigar case-bearer, 

 in its mining and making of new cases, seems to devour more actual leaf 

 surface and thus, presumably, obtain more poison than would be the case 

 with the larch case-bearer. In order to test this method, however, five 

 larch trees well infested with the case-bearers were sprayed with arsenate 

 of lead at the rate of 2^ pounds to 50 gallons of water. These trees were 

 thoroughly sprayed on April 25. The buds were just starting to grow 

 well and the case-bearers were just coming on them from their winter 

 quarters. 



The trees were examined from time to time, but no appreciable diminu- 

 tion in the numbers of case-bearers could be noted. 



On May 5 the trees, with one exception, were carefully and thoroughly 

 sprayed again. At this time the leaves were of fair size and the case- 

 bearers were abundant. 



The trees were observed throughout the season, but no difference in 

 the amount of injury could be seen between these and many others 

 untreated. 



In looking over the trees shortly after they were sprayed, the poison 

 was found to be invariably gathered in small globules at the bases of the 

 leaves. The leaves of the larch are small, narrow, and glossy. The poison 

 does not seem to stick to the narrow needles and consequently does not 

 become well distributed over the surface of the leaves. It is possible that 

 a small quantity of soap added to the mixture would enable the poison 

 to spread and stick better. 



Laboratory experiments with arsenate of lead gave very inconclusive 

 results. 



In the light of experiments at this station, the writer would not feel 

 justified in recommending the use of arsenate of lead for control of the 

 larch case-bearer. 



Lime-sulfur 



From experience gained in controlling the bud moth on pecans and the 

 ribbed cocoon-maker on apples by spraying the trees in the dormant 

 season with lime-sulfur, thus killing the hibernating larvae and pupae, 

 it seemed possible to do the same with the larch case-bearer. Accord- 

 ingly, on April 7, 1911, before the buds had begun to swell and before 

 the larvae had left their winter positions, a badly infested tree was sprayed 



