ANNUAL REPORT, 1936 57 



Studies of Scolytus multistriatus. Preliminary studies on the life history in 

 Massachusetts of the smaller European elm bark beetle, Scolytus multistriatus, 

 are being made. This is the beetle which today is considered to be the principal 

 vector of the Dutch elm disease organism. Studies indicate that there may be 

 only one generation a year in this region. Some scouting was done in Western 

 Massachusetts for additional records of the presence of this beetle, near the 

 localities where the insect was found last year. To date no additional outbreaks 

 have been found. However, H. rufipes has been present wherever scouting was 

 done. 



Other Elm-Boring Insects. Experimental work was also conducted on the 

 habits of two other elm-boring insects, Saperda tridentata and Magdalis sp. 



Campus Insect Pest Survey. A survey of insect pests present on the 

 shade and ornamental trees (elms, particularly) on the Massachusetts State 

 College campus was made for the purpose of assembling information for a spray 

 program. 



Apple Leaf-Curling Midge. (W. D. Whitcomb, Waltham.) The apple 

 leaf-curling midge (Dasyneura mali Kieffer) was as abundant in the infested 

 area in 1936 as at any time since it was discovered. In parts of some orchards 

 all new shoots and watersprouts which were susceptible during the oviposition 

 periods of the midge flies were attacked. In Westford a distinct and abundant 

 third generation developed on young trees from eggs laid August 20 to 

 September 1, but in the same orchard on older bearing trees having a good 

 crop of fruit and little or no new growth in August, the number of third genera- 

 tion midges was insignificant or none could be found. 



A new infestation of this midge was found at Groton, Massachusetts, which 

 extends the infested area nearer to the large apple growing section of the east- 

 central part of the State. This new infestation apparently was caused by wind- 

 blown midge flies during the spring emergence period, and indicates that further 

 spread of this pest by natural agencies may be expected. Other new infesta- 

 tions were reported and verified at Sanford and Alfred, Maine, and near Roches- 

 ter, N. Y. The Maine infestation also appears to be the result of spread by 

 wind from a previous known infestation in southeastern New Hampshire. 



Collections of mature maggots on cloth-covered frames under specimen trees 

 were concentrated in three periods coinciding with the generations. Maximum 

 collections were made on June 12, August 7, and September 1. Rainfall which 

 softened the rolled leaves influenced the exact time of emergence. Rain fell at 

 approximately the time when the maggots of the first and third generations 

 reached maturity and emergence was normal for the development, but the 

 records indicate that the absence of rain between July 24 and August 7 delayed 

 the maximum emergence of the second generation maggots about 10 days. 



By placing bands and tanglefoot on the trunk of the trees under which the 

 cloth-covered frames were erected, it was determined that approximately 10 

 percent of the mature maggots crawl down the tree and 90 percent of them fall 

 from the leaves and branches. 



Corrugated paper bands treated with Beta-Naphthol captured as many 

 maggots on the trunks and branches as did bands of leather, felt, or canvas, 

 indicating that the chemical is not repellent. In the chemically treated bands 

 34 percent of the maggots were on the band, 28 percent in the corrugations, and 

 38 percent on the bark under the band. All maggots in or beneath the treated 

 bands were dead except a few which spun cocoons in crevices in the bark under 

 the band but not in contact with the chemical. 



