38 



BULLETIN 847, IT. S. DEPARTMENT OF AGRICULTURE. 



at Elkins. The liquids were applied with a paintbrush to the lower 

 portion of the tree trunks as soon as it could be determined that all 

 of the eggs of the season had hatched. The applications were made 

 on August 16 to 17, and the trees examined for results 8 weeks later. 

 The results of the treatments are set forth in Table XII. It should 

 be borne in mind that all the borers considered in the table were 

 newly hatched individuals that were feeding beneath only a thin 

 layer of bark. 



Table XII. — Effect upon newly hatched roundheaded apple-tree borers of vari- 

 ous liquids applied to the bark over the regions where they ivere feeding. 



Material used. 



Number 



Number of borers found — 



of 



trees 











treated. 



Alive. 



Dead. 



Total. 



60 



26 



20 



46 



60 



13 



53 



66 



60 



22 



16 



38 



60 



28 



28 



56 



60 



15 



31 



46 



Per cent 

 of effi- 

 ciency. 



Nicotine sulphate, 1 part to 10 parts of water 



Nicotine sulphate, undiluted 



Raw linseed oil 



Standard kerosene emulsion 



10 per cent solution sodium arsenate, mixed with 

 equal part of kerosene emulsion 



43.5 

 80.3 

 42.1 

 50 



67.4 



It will be seen from Table XII that many borers may be killed by 

 saturating the bark over where they are feeding with irritants and 

 poisons of a penetrating nature, provided that the treatments are 

 applied while the borers are still small and feeding in shallow bur- 

 rows. All the materials used in the foregoing test killed a consid- 

 erable number of borers, the undiluted nicotine sulphate giving best 

 results. None gave complete control, and it is a question whether 

 their use would be justified in orchard practice. Trees so treated 

 would have to be gone over and wormed subsequently in order that 

 entire freedom from borers mi^ht be assured. 



SPRAYING WITH ARSENATES TO KILL THE ADULTS. 



Feeding on the exposed surfaces of the apple and other host 

 trees seems to be a general habit of the beetles. The bark of twigs 

 and leaf stems and the tissues of the leaf are eaten. (PI. IX, A, C.) 

 Beetles were often observed manducating castings thrown out from 

 the trees by larvae, evidently for the moisture which the castings con- 

 tained. The bark and leaf surface eaten away by one female totaled 

 6.9 square inches. This feeding habit suggests the use of poison 

 sprays as a possible means of killing the beetles. In one small-scale 

 experiment six newly emerged beetles were killed by applying a lead- 

 arsenate spray to the foliage of a small apple tree over which they 

 were caged. All died before the females were ready to oviposit. 



In extreme cases of infestation it would probably be profitable to 

 apply arsenical sprays to young apple orchards primarily for the 



