ANNUAL REPORT, 1935 51 



that Hylurpoginus rufipes breeds in dead and dying elms and later attacks 

 apparently healthy elms in which it digs overwinter tunnels makes this beetle 

 especially important as a possible vector of the Dutch elm disease in the event 

 it comes in contact with the disease. 



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

 leaf curling midge, (Dasyneura mail Kieffer) was normally abundant in 1935 

 in the infested area, although its principal development was confined to two 

 generations as compared to an apparent moderate third and a small fourth 

 generation in other seasons. No definite increase in the known infested area 

 was discovered. 



It was determined that pupation in the overwintering cocoons begins with 

 the approach of warm spring weather, and the average pupal period was 9.75 

 days. 



In the orchard, flies of the overwintering generation were abundant from 

 blossom time (about May 20 ) until June 4. Eggs and newly hatched larvae 

 were plentiful during this same period and mature maggots began to leave the 

 rolled leaves by June 18, with large numbers on June 25 and July 9. Flies of 

 the first generation were abundant from July 12 to July 30. New growth 

 suitable for oviposition was limited at this time but that which was available 

 was thoroughly infested with eggs and young maggots. Mature maggots of 

 this generation migrated from the rolled leaves in large numbers on July 30 

 and continued for about a month, being especially noticeable on August 6 and 

 23. Development in September was insignificant. 



Positive evidence was secured that migration of mature maggots from rolled 

 leaves is dependent on moisture. Based on precipitation records, at least 3/10 

 of an inch of rain was necessary to cause a noticeable migration from the leaves. 



In 1935, 87.8 percent of the maggots which were collected on July 9 trans- 

 formed to flies during the current season, but of those collected on July 12 and 

 July 30 only 5.17 percent and 7.89 percent respectively transformed. Since 

 the absence of suitable buds for oviposition in late summer would greatly reduce 

 the population, this ability to hold over is an important factor in the continua- 

 tion of an infestation. 



The number of mature maggots collected under felt bands on the trunk and 

 branches, and on 18 square feet of cloth under the tree, averaged about 1500; 

 but since the cloth covered only about one-fourth of the area under the tree, 

 this indicates that approximately 80 percent of the maggots fall to the ground 

 and 20 percent crawl down the branches. 



The addition of 40 percent nicotine sulfate 1-800 to the regular calyx spray 

 reduced the average number of midge eggs from 169.8 per bud where no nicotine 

 was added to 87.6 per bud, and the average number of developing larvae from 

 278.8 to 202.6 per twig respectively. In both cases, however, the number of 

 infested buds per tree was approximately equal. 



Calcium cyanide at the rate of 1 and 2 pounds per 100 square feet, and naph- 

 thalene flakes at the rate of 2 and 3 pounds per 100 square feet, applied to the 

 soil under the trees just before fly emergence, reduced the number of flies from 

 61 to 80 percent but were slightly less effective than similar treatments in 1934. 



Experiments indicated that about 90 percent of the maggots which crawl 

 down the trunk of the tree can be collected under 2-inch felt bands and that 

 leather bands are also satisfactory. Corrugated paper bands treated with beta- 

 naphthol, when tried late in the season, were not repellent and killed all maggots 

 which entered them. 



Laboratory experiments with potted apple trees indicated that spraying with 



