ANNUAL REPORT, 1941 21 



DEPARTMENT OF BOTANY 



A. Vincent Osmun in Charge 



Diseases of Trees in Massachusetts. (M. A. McKenzie and A. Vincent 

 Osmun.) 



The Dutch Elm Disease Problem. For several years in the cooperative program 

 for the study of the Dutch elm disease in Massachusetts, intensive effort has 

 been concentrated in Berkshire County as new stations for the causal fungus, 

 Ceratostomella ulmi (Schwarz) Buisman, were reported in nearby New York and 

 Connecticut. During recent years, the circulation of numerous false reports 

 that the disease was present in Massachusetts, and even the publication of 

 photographs of trees removed because they were affected by the disease have 

 sometimes confused and alarmed the public. At least a part of the confusion 

 has resuhed from the failure to distinguish between the fungus which causes 

 the Dutch elm disease and the principal carrier insect, Scolylus miiUistriatus 

 Marsh., which is a bark beetle infesting certain areas of Massachusetts, notably 

 southern Berkshire County and the region east of Worcester County. 



The spread of the disease into Massachusetts was delayed for several years 

 by the eradication of diseased trees in the adjoining states, although early in 

 1941 it was pointed out^ that elms in southwestern Massachusetts were in im- 

 mediate danger from the encroachment of the disease on Berkshire County 

 from New York on the west and Connecticut on the south. However, in Septem- 

 ber 1941 the first Massachusetts elm in which the presence of the disease could 

 be officially established, was eradicated — a young tree about 20 feet in height 

 growing on private property in the town of Alford. Typical symptoms of foliage 

 wilting and streaking of the woody parts were present. The Scolytus beetle 

 was not found in the tree but has been observed in the town. In the vicinity 

 of the diseased tree and elsewhere throughout Massachusetts, hundreds of other 

 trees showing symptoms macroscopically indistinguishable from those of the 

 Dutch elm disease were checked in field and laboratory studies during the past 

 year, but no additional trees with the disease have been discovered. The work of 

 the organized project of this Station in collecting and studying specimens from 

 suspected trees has been supplemented by other public and private groups and 

 by individuals, including the Massachusetts Department of Agriculture, the 

 United States Department of Agriculture, the Massachusetts Forest and Park 

 Association, town and city tree wardens, employees of other municipal and state 

 departments,- arboriculturists, public utilities, and private citizens. 



The most constructive procedure in attempting to check the spread of the 

 disease is the removal of all elm material in such a condition as to be attractive to 

 carrier beetles. The quantity of such material present in any location may be 

 related to a number of factors, as in southern Berkshire County where drouth 

 injury and repeated attacks of leaf-chewing insects have seriously weakened 

 many elms in such a manner as to make them suitable for infestation by beetles; 

 and the destruction of this material will doubtless prove of inestimable value in 

 limiting the population of carrier beetles of the Dutch elm disease fungus. 



Other Tree Problems. Sixty-nine diseases of thirty-four species of trees, in- 

 cluding eleven diseases of elm were identified from more than 500 specimens and 

 inquiries received during the year. The Cephalosporium wilt of elm was reported 

 from 21 municipal'ties in which no previous cases of the disease were reported, 



'McKenzie, Malcolm A. The Dutch elm disease problem in Massachusetts. Published in 

 "Progress Report including Transcriptions of Certain Papers presented at the Eighth Annual 

 Five-Day Short Course for Tree Wardens and Other Workers with Trees," M. S. C, March 28, 

 1941. 



