50 MASS. EXPERIMENT STATION BULLETIN 327 



Insects Concerned in the Dispersal of Dutch Elm Disease. (W. B. 



Becker. ) A study was made of the present distribution of the elm bark beetles 

 concerned with the spread of the Dutch elm disease. The material which was 

 collected by scouts and supervisors in the State ERA project on this disease 

 formed the basis of this survey. Although not all of the towns in the State 

 were scouted, sufficient material was received from all sections of the State to 

 furnish an accurate working knowledge of the distribution of the beetles likely 

 to be vectors of the Dutch elm disease before it actually enters the State. 



Scolytus multistriatus, the species of European elm bark beetle known to 

 transmit the disease, was taken from several towns in Essex, Middlesex, and 

 Plymouth Counties, well outside its previously known range in eastern Massa- 

 chusetts. Specimens of elm bark and wood from the towns of Westfield and 

 Egremont in western Massachusetts also showed the presence of this species. 

 However there is an infestation of these beetles which centers at the Port of 

 New York and which extends to points in Connecticut and New York State 

 which are quite close to these two towns in western Massachusetts, so it is 

 probable that the beetles spread to Egremont and Westfield from the New York 

 infestation rather than from the infestation surrounding Boston. Altogether 

 forty-seven specimens of elm wood showing Scolytus multistriatus infestation 

 were received. 



The American elm bark beetle, Hylurgopinus rufipes, (a native of this 

 country) which has also been associated with cases of the Dutch elm disease, 

 was found distributed over practically the entire State. One hundred and 

 nineteen specimens of Hylurgopinus rufipes were received. A study of the 

 records taken this summer showed that about 40 percent of the bark beetle 

 infestations found were in elm log piles. This information brings out the fact 

 that these beetles breed extensively in elm logs. Therefore any sanitation 

 measures applied to standing trees must also include a clean-up of elm log 

 piles in order to eliminate the places where these bark beetles breed. Recently 

 cut elm logs are especially favorable to attack by the beetles. 



The large elm borer, Saperda tridentata, and the elm snout beetles, Magdalis 

 sp., were often found in the same piece of wood with both of the elm bark 

 beetles mentioned above. 



Two hundred and fifty-four specimens of shade tree insects or their injury 

 were received. Two hundred and fourteen of these were elm insects. 



Circulars were sent to all the tree wardens in the State calling attention to 

 the seriousness of the damage which is being done to the foliage of our elm 

 trees by the elm leaf beetle, Galerucella xanthomelaena. Injury due to this 

 insect can mask the symptoms of the Dutch elm disease if it should happen 

 to be present, thus making scouting for the dread disease inefficient. Trees 

 defoliated by this insect are weakened and thus put into a favorable condition 

 for the breeding purposes of the bark beetles which are known to be capable 

 of transmitting Dutch elm disease. 



Life history studies of the American elm bark beetle, Hylurgopinus rufipes, 

 were undertaken. Very little has been previously known of its life history and 

 habits. It overwinters abundantly in Amherst, in short tunnels which it digs 

 into and through the bark of apparently healthy trees. In the early spring it 

 emerges from these tunnels and in the latter part of May was noticed attacking 

 trap logs which were set out for the purpose. Dying parts of elms were also 

 observed to be attacked. Only one generation of beetles was reared in the field. 

 They began to emerge about the first of August; reached the peak of emergence 

 on August 20; and gradually lessened until the cold weather set in. The fact 



