44 MASS. EXPERIMENT STATION BULLETIN 449 



Dormant applications: DDT emulsions, 1 and 2 percent, gave good, sometimes 

 complete, protection at the top of an elm 41 days later. After 64 days, protec- 

 tion at the top was poor to fair from the 1 percent emulsion and poor to good from 

 the 2 percent emulsion. After 112 days, protection was practically all poor at 

 the top. No spray injury to the elms resulted. 



Foliage applications: In mid-August these same elms were sprayed again and 

 others- sprayed for the first time. Special attention was given to spraying the 

 tops. With 1 percent DDT emulsions, protection at the tops was poor to good 

 67-70 days later, but mostly poor after 117 days. With 2 percent DDT emulsions, 

 protection at the tops was good after 67-69 days and fair to good after 117 days. 

 Little to no injury to the elms resulted from these applications. 



3. With Mist Blowers: The mist blower described in last year's annual report 

 (Bulletin 441, p. 42) was used again. When the low dosages reported as success- 

 ful against gypsy moths and other defoliating insects on shade trees (up to 1 

 quart of a 12 percent DDT solution or emulsion per medium to large elm) were 

 applied in these experiments or with a similar mist blower on a regular municipal 

 tree spraj'ing operation, good protection against twig feeding by S. multistriatus 

 was not obtained at any height, even after only a few days of weathering. 



Dormant applications: When one gallon of a 12 percent DDT solution (diluted 

 with kerosene) was sprayed at a medium to large elm, protection at the top was 

 poor 43 days later. Two gallons gave somewhat better results then, but very 

 poor results after 73 days. Three gallons gave good results at the top after 71 

 days but poor results after 148 days. None of these applications caused notice- 

 able injury to dormant elms, but a sugar maple growing close to the elm which 

 received three gallons was severely injured by the spray. 



Foliage applications: One gallon of a 12 percent DDT emulsion, applied per 

 tree in mid-August, gave poor results 43 days later at the top of a tree which had 

 not been previously sprayed. Protection at the tops was fairly good from two 

 and three gallons per tree after 44 days, but was poor after 77 days from two 

 gallons and only slightly better from three gallons. Better protection was always 

 obtained in the lower parts of the trees and was in proportion to the amount 

 sprayed at the tree. These mid-August foliage applications caused little notice- 

 able injury to the elms, except on the lower branches of the tree which received 

 three gallons of the emulsion and where the blower passed too close to the other 

 trees. 



4. With an Airplane. Through the courtesy of the Field Headquarters, 

 Gypsy and Browntail Moth Control, of the U. S. Bureau of Entomology and 

 Plant Quarantine, and the Entomology Department of the Connecticut Agri- 

 cultural Experiment Station, the effectiveness of airplane applications of DDT 

 against twig feeding of 5. multistriatus was studied. Deciduous forest areas in 

 Connecticut were sprayed by airplane early in the spring with DDT at dosages 

 used experimentally to combat gypsy moth caterpillars. Flying and spraying 

 conditions were reported excellent, no foliage was yet present, and all glass 

 plates at the site of these experiments, both on the ground and on branches, 

 were well covered with the spray. Prevention of S. multistriatus feeding was 

 unsatisfactory throughout the tests, which lasted 48 days. Even after only 

 three days of weathering on a plot sprayed with as much as 2 pounds of DDT 

 (technical grade) dissolved in 2 gallons of liquid (xylene and kerosene) per acre, 

 only 45.4 percent prevention was obtained. All elm twigs used in this test were 

 from branches 20 to 30 feet high in the tree. 



