64 MASS. EXPERIMENT STATION BULLETIN 388 



eggs were found on every bud examined, namely May 27 to June 10, July 1 to 8, 

 and July 22 to August 5. During the first two periods 100 tips were examined 

 at each observation; but in the last period the number of tips available averaged 

 less than 10, contrasted with 1940 when a large number of tips was available 

 until about August 25. In 1941 the first eggs were found on May 9 which is 15 

 days earlier than in 1940. 



Maturity of larvae and their emergence from rolled leaves was concentrated in 

 three definite periods on June 17 to 24, July 8, and July 29. These periods gen- 

 erally correspond with the rainfall rather than with the development of genera- 

 tions which was extended and overlapped by abnormal weather conditions. 

 The relative abundance of the midge throughout the summer is indicated by the 

 number of larvae collected in 5 bands as follows: June 17, 2280; July 8, 244; and 

 July 29, 790. 



In a newly infested orchard at Waltham containing 96 trees of 7 varieties of 

 approximate equal exposure to infestation, 893 infested buds were collected on 

 June 12. The average number of infested tips per tree of each variety was: 

 Delicious, 42.00; Rhode Island Greening, 8.75; Baldwin, 7.58; Mcintosh, 4.54; 

 Gravenstein, 3.16; Northern Spy, 0.33; and Wealthy, none. In this collection 

 63.29 percent of the infested tips were found on the Delicious trees. Another 

 collection on July 9 yielded 532 infested tips on the same trees, making a reduc- 

 tion of 40.42 percent due to destruction of the maggots in the infested tips at 

 the previous collection. , 



Similar collections from a nearby orchard where 396 infested tips were col- 

 lected on 54 small trees showed an infestation of 11.94 tips per tree or 57.32 

 percent of the total on Starking; 6.00 per tree on Golden Delicious; and 3.58 per 

 tree on Baldwin. In a block of young trees, 2 Milton trees had an average of 

 24.5 infested tips, indicating high susceptibility. At the same time no infested 

 tips were found on 15 Macoun trees. 



Continued experiments with naphthalene broadcasted at the rate of 2 pounds 

 per 100 square feet showed that the treatment reduced the number of midge 

 flies emerging from the soil and duff 79 percent at the first generation and 97 

 percent at the second generation. 



Larvae and pupae in cocoons under the rough bark on the trunk of the trees 

 were killed by experimental spraving with dormant sprays. Applications to the 

 bark were made Apri! 1 1 and July 1 using Elgetol (Standard Agricultural Cheniical 

 Company) 1 percent, Spra-Cream (B. G. Pratt Company) 3 percent actual oil, 

 and Spra-Cream 3 percent plus DNOCHP (Dow Chemical Company) 15 ounces 

 per 100 gallons. Cages enclosing 3 feet of the tree trunk were built around the 

 sprayed trees. In these cages 84 flies of the first generation and 40 flies of the 

 second generation were collected from the unsprayed tree, while only 2 flies were 

 found in any of the cages on sprayed trees. Emergence of flies from mulch col- 

 lected under trees where the above dormant sprays were applied at the rate of 

 2 gallons per 100 square feet indicated that considerable mortality of the midge 

 resulted where Elgetol was applied but that the oil emulsion treatment was not 

 effective. 



Control of Plum Curculio in Apples. (W. D. Whitcomb, Waltham.) In spite of 

 unseasonably' warm weather during the pre-blossom and blossom period of apples, 

 the critical period of curculio activity did not occur until May 20-23 which was 

 five to eight days after the petal-fall stage. This period was characterized by 

 maximum temperatures above 85° P., but it was apparent that the suitable 

 development of the fruit for feeding and oviposition was the most important 

 attraction to the beetles. 



Blocks of eight trees each were sprayed with lead arsenate 4 pounds, wettable 



