ANNUAL REPORT, 1939 27 



fungus disease itself. It must be understood clearly that no population of carrier 

 insects, however large, can initiate the Dutch elm disease independently of the 

 aiusal fungus, Ceralostomella ulmi (Schwarz) Buisman. Of course, if the fungus 

 is accessible to a large population of earners, the spread of infection associated 

 with the disease may be facilitated greatly. Therefore, control of the carriers 

 is essential to any program directed against the spread of the fungus, and the 

 67 VV. P. A. municipal tree projects in operation throughout Massachusetts during 

 the past year had as one objective the cui'tailment of carrier populations which 

 infest dead and weakened trees or parts of trees. Such programs should prove 

 of considerable value against the day when the Dutch elm disease may be found 

 in Massachusetts. In view of the widespread distribution of the oldest known 

 American infestation of the imported smaller European elm bark beetle carrier 

 in eastern Massachusetts, and the more limited infestation in Berkshire County, 

 Massachusetts faces a serious Dutch elm disease problem on the western as well 

 as the eastern front, even though the disease is not now known to be in the State. 



Other Tree Problems. Sixty-eight fungus diseases of thirty-three hosts, in- 

 cluding eleven diseases of elm, were identified from specimens received for diag- 

 nosis during the year. 



The Cephalosporium wilt disease of elm has been found to be rather widespread 

 in Massachusetts and has been the subject of field and laboratory investigations 

 over a period of several years. Results have been published in Bulletin 368. 



A serious fungus disease of the London Plane-tree, an exotic, hybrid, ornamental 

 sycamore widely planted in parts of eastern United States, has been reported as 

 causing serious damage in New Jersey and certain other locations outside of New 

 England. Numerous inquiries relative to this disease have been received during 

 the year, but thus far the disease has not been found upon the sycamores in New 

 England, although the native sycamore is supposedly susceptible to infection 

 by the causal fungus, Ceralostomella sp. Sycamores in this section are subject 

 to the Sycamore Blight, caused by Gnomonia veneta (Sacc. and Speg.) Kleb., 

 which commonly affects leaves and twigs. Possibly the recently reported disease, 

 which kills the trees, in part at least, by the growth of a canker, may escape 

 early detection because the public has become accustomed to seeing leaves wither 

 in association with the common blight. 



Winter injury was a common cause of tree disorder this year. Deciduous plants 

 as well as evergreens suffered severely from this trouble in addition to serious 

 secondary injury from the effects of the hurricane of September 1938. Injuries 

 traceable to the hurricane continue to be sources of numerous inquiries. In order 

 to facilitate the handling of these inquiries, a series of ten brief circulars has been 

 prepared to supplement the general information on the repair of hurricane dam- 

 aged trees included in Extension Circular 30. Also, at the request of the Massa- 

 chusetts Tree Wardens' and Town Foresters' Association, a report on the hurri- 

 cane in Massachusetts was prepared for their publication, "Proceedings of the 

 Twenty-eighth Annual Meeting, February 8 and 9, 1939." 



Crown Rot of Dogwood. (C. J. Gilgut.) This disease, caused by Phytophthora 

 cactorum (L. & C.) Schroet., is serious to ornamental flowering dogwoods and is 

 present in Massachusetts. The organism kills the bark at the base of the tree, 

 thus girdling it and causing its death. A number of chemicals were determined 

 to be toxic to the organism growing on artificial media. Materials which proved 

 toxic are a solution of methyl alcohol and resin, equal weights of each, Bordeaux 

 paint, aqueous solution of mercuric bichloride 1 to 1000, saturated alcoholic 

 solution of mercuric bichloride, turpentine, malachite green 1 to 1000, copper 

 sulfate solutions 1 to 10 and 1 to 100, Semesan 1 to 1000, and a saturated solution 

 of potassium permanganate. Materials which proved nontoxic are pentachloro- 



