326 OHIO EXPERIMENT STATION: BULLETIN 332 



THE BRONZE BIRCH BORER 



(Agrilus anxius Gory) 



Description. The bronze birch borer is a comparative new- 

 comer in Ohio, but the record of its destructiveness since its en- 

 trance into the state is quite as disturbing to the lovers of the 

 beautiful white birch and other birches as well as to those in other 

 states who have known the pest for a longer period. 



The adult of the bronze birch borer is a slender beetle about 

 one-half of an inch long, olive-bronze in color ; the larva or borer is 

 a little longer, measuring about three-fourths of an inch. It is foot- 

 less, slender, flattened and creamy-white in color. Both adult and 

 larva are shown in Plate LXX,' Fig. 2. The insect is best known, 

 however, not from its own characteristics and appearance but by- 

 reason of its work in birches and particularly the white birch. 



Life history and habits. The insect passes the winter in the 

 full-grown larval stage in a cell made in the wood of the host not 

 far from the bark. In early spring of the following year the larvae 

 change to pupae and a little later the adults begin to emerge. As to 

 the exact date of the appearance of the adults, however, there seems 

 to be some variation. Some diversity of opinion exists among 

 entomologists though it may be stated that the adults probably 

 appear in May or June, and in all likelihood the largest numbers 

 appear during the latter month. This point as will be noted later 

 is of considerable importance in the control of the species. 



The eggs are laid in crevices in the bark in June and the larvae 

 upon hatching bore into the bark of the host. At first the tunnel 

 lies close under the bark, but as the work of the feeding larva con- 

 tinues, the burrow is extended without any particular definiteness 

 as to form or direction, now deeper into the wood ; now up near the 

 bark; extending this direction and that until it becomes a much 

 convoluted affair. The general result is the riddling of the tissues 

 of the host in the immediate vicinity of the burrow and the forma- 

 tion of a dark reddish-brown spot above on the bark. 



Larval growth is completed by October and the insect goes into 

 hibernation. 



Nature of .work. As previously indicated this insect is a borer. 

 It starts in the upper branches of the host and as a direct result of 

 the riddling by the feeding larva the upper part of the tree dies. 

 The dying of the top of a prized ornamental is in many instances 

 the first indication of the presence of the pest in the vicinity. 

 Later, through the continued activity of the insect the entire tree 

 dies. 



