i8o 



Journal of Agricultural Research 



Vol. Ill, No. a 



several feet and in badly infested trees are so numerous that the roots 

 often die, causing a weakening of the whole tree. 



The work of the insect is obscure, there being no chips or castings 

 thrown to the surface, as is the case with the common roundheaded 

 apple-tree borer. The egg, which is placed rather conspicuously on the 

 bark of the trunk, and the exit hole in the bark through which the adult 

 escapes from the wood, are the only external marks made by the insect 

 on the tree. In addition to the injury resulting from the dam'aged roots, 

 the exit holes in the bark admit more or less water, which frequently 

 induces decay of the heartwood. The harm one individual root borer 

 is capable of doing to a tree is much less than that usually done by a single 

 roundheaded apple-tree borer, but in the localities where investigations 

 were made the former species outnumbered the latter. 



At French Creek, W.Va., 345 apple, pear, and service, or shadbush, trees, 

 from yi inch to 5 inches in diameter were cut off a few inches above the 

 ground, and the burrows made by the larvae of both species in ascend- 

 ing the trunks to pupate were counted. The three species of trees are 

 favorite food plants of both of these borers, and the results of the counts, 

 recorded in Table I, give an idea of the relative abundance of the two 

 borers in the one locaUty. Similar results were obtained in several other 

 localities where fewer trees were examined. 



Table I. 



-Relative abundance oj burrows of Agrilus vittaticollis and Saperda Candida 

 in apple, pear, and service trees 



Kind of trees. 



Apple 



Pear 



Service 



Total 



Number of 

 trees. 



125 



20 



200 



34S 



Number of 



burrows of 



Agrilus. 



3" 



9 



342 



662 



Niunber of 



burrows of 



Saperda. 



lOI 

 o 



Most of the apple and pear trees cut for the foregoing counts were 

 such seedlings as could be found in roadside fence corners and neglected 

 orchards, and the service trees were in the woods. Only 36 of the 125 

 apple trees, or about 28 per cent, were free from the burrows of Agrilus 

 and 87, or about 70 per cent, were free from burrows of Saperda. 



FOOD PLANTS 



The adult of this insect has been recorded by various writers as fre- 

 quenting the foliage of service, wild thorn, and chokeberry. The ^vTiter 

 has found the larv^a attacking apple, pear, wild thorn, wild crab, and 

 service. It has been found rather abundantly in the following West 

 Virginia localities: French Creek, Cherry Run, Sleepy Creek, Spring- 

 field, Moorefield, Romney, Keyser, Flkins, and Junior. Mr. E. B. 

 Blakeslee, of the Bureau of Entomology, has found the larva in service 

 trees at Winchester, Hayfield, and Staunton, Va. Of the several larval 

 food plants named, apple and service seem to be greatly preferred above 

 the others. 



