20 MASS. EXPERIMENT STATION BULLETIN 449 



DEPARTMENT OF BOTANY 

 A. Vincent Osmun in Charge 



Diseases of Trees in Massachusetts. (M. A. McKenzie, A. Vincent Osmun 

 and D. H. Marsden.) 



The Dutch Elm Disease Problem. The first discovery of the Dutch elm disease 

 in Massachusetts was in 1941, when a tree in Alford, Berkshire County, was 

 found to be infected by the causal fungus, Ceratostomella ulmi (Schwarz) Buisman. 

 As of July 6, 1948, the disease fungus has been isolated from 1422 elm trees of 

 94 municipalities in 11 counties on the mainland of Massachusetts; Barnstable, 

 Dukes, and Nantucket being reported as disease-free at present. Those towns 

 with a relatively large population of weed elm trees are confronted with a diffi- 

 cult disease control problem; but where the number of elms is more restricted 

 and the trees have received the care given valued trees, practical disease control 

 should be possible. Three distinct zones of build-up in disease are apparent in 

 the State. From the original outbreak, the disease has spread rather widely in 

 Berkshire County. In the Connecticut Valley region, the increase in the num- 

 ber of diseased trees has been conspicuous in the last three years; and more 

 recently in eastern Massachusetts, elms in the vicinity of Boston have been 

 seriously affected. The spread of the disease from year to year is shown by the 

 following table: 



Year 



1941 



1942 



1943_ 



1944 _ - 



1945.__ - 



1946 



1947 - 



1948 (July 6).. 



In studies to determine the spread, build-up, and possible benefits of combative 

 measures, laboratory diagnosis of specimens is required for accurate deiermina- 

 tion of the causal fungus. The specimens are collected by scouts trained in the 

 detection of characteristic symptoms on trees suspected of the disease. Diseased 

 trees are reported to the Massachusetts Department ot Agriculture and that De- 

 partment carries out a cooperative disease control program with municipal govern- 

 ments or agencies responsible for affected trees. In a prepared schedule sanita- 

 tion and other measures designed to restrict the spread of the disease are outlined 

 for varying local conditions. These measures are presently under further study, 

 including experiments in cooperation with the Department of Entomology on 

 the use of spray materials for the control of bark beetles which serve as vectors 

 of the disease fungus. 



In general, the rate of increase in the number of diseased trees reported is 

 most conspicuous in those areas where suppressive measures are lacking, poorly 

 timed, or misapplied. Delay in the application of disease restrictive measures is 

 costly, and expected benefits may be tragically nullified if essential work awaits 

 a convenient assignment. 



