BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 
39 
tional confirmations were reported, and late in May and early in June 
4 more were discovered, giving a total of 22 in this general area. 
These trees, plus some associated beetle material, were eradicated by 
the State. The total area involved is a strip 30 miles wide running 
northeast through central Frederick County. This is the first reap- 
pearance of the disease in Marylnd since 1941, and in Frederick County 
since 1935, when 3 diseased trees were found in Brunswick. 
The exploratory scouting indicated that the Scolytus multistriatus 
(Marsh.) infestation near Boston is continuous through Massachu- 
setts to the main disease area in New York, where these bark beetles 
are the principal carriers of the fungus causing the disease. A scout 
crew traced an infestation of this species down both sides of the Mis- 
sissippi River as far as northern Mississippi and west of the river in 
Arkansas. S. multistriatus was also found well established in the 
Indianapolis area. 
In the effort to develop means whereby individuals or municipal- 
ities may protect their own trees from the Dutch elm disease, experi- 
mental plots have been established at Morristown, Princeton, and 
Ridgewood, N. J. At Morristown a circular area having a radius of 
3 miles is being intensively scouted as in former years. In the inner 
2 miles trees showing symptoms of the disease are removed as promptly 
as possible, the outer mile serving as a buffer zone. In this inner 
area confirmations from 1939 to 1912 numbered 72, 13, 7, and 22, and 
increased to 140 in 1943. 
As a check on disease incidence within the heavily infected terri- 
tory where organized control work has been abandoned, scouting was 
continued in plots each 5 miles in radius at Princeton and Ridgewood, 
N. J. Here also pronounced increases in the number of diseased trees 
were found this year. The Ridgewood plot in 1943 yielded 292 con- 
firmations, as contrasted with 115, 85, and 71 in the 3 preceding 
years. Confirmations at Princeton increased from 75, 93, and 16 to 
208 confirmations in 1943. 
Scouts submitted 14,213 samples to the laboratory for culturing; 
1,736 of these were infected. Connecticut had 122 confirmations, Mas- 
sachusetts 13, New Jersey 845, New York 386, Pennsylvania 252, and 
in the isolated infected areas Maryland 22, Ohio 92, and Indiana 4. Of 
the New Jersey confirmations, 809 occurred in experimental check plots 
inside the disease area. Since area-wide, systematic eradication work 
was discontinued in 1941, total confirmations for this year or either 
of the previous 2 years are not indicative of intensification or diminu- 
tion of the disease in the main area. 
Cumulative totals since discovery of the disease in 1930 show 67.374 
known cases of the disease. Of these 2,026 have been found in Con- 
necticut, 20 in Massachusetts, 50.847 in New Jersey, 12,843 in New 
York, 1,265 in Pennsylvania, and 373 in the isolated areas. 
ERADICATION AND SANITATION ACTIVITIES 
Prior to abandonment of tree-removal work in February, crews had 
destroyed 510 confirmed trees and 1.157 elms or other elm material 
containing bark beetle infestation. During the remainder of the year, 
through State and municipal cooperation, an additional 43 diseased 
trees and 60 beetle-infested items were eradicated. In addition, 198 
elms were pruned of bark beetle material. 
