ANNUAL REPORT, 1945-46 . 19 



1. Destroy all elms affected by Dutch elm disease. 



2. Remove and burn promptly bark from any cut elm wood. 



3. Avoid piling elm wood in the open unless it is peeled. 



4. Don't transport elm wood with bark attached. 



5. Spray elms to control leaf-eating insects. 



6. Keep elms as healthy as possible. 



Additional methods of disease control are being explored, and in cooperation 

 with the Department of Entomology the uses of spray materials for control of 

 carrier-insects are under investigation. 



Other Tree Problems. Fifty-three diseases of twenty-seven species of trees 

 including nine diseases of elm were identified from approximately 400 speci- 

 mens and inquiries received during the year. The Cephalosporium wilt of elm 

 was reported from three additional municipalities in Massachusetts. Verticillium 

 sp. was isolated from several species of woody plants. 



During the year, postwar planning of municipal tree programs was rapidly 

 accelerated. The most conspicuous and obvious need is treatment of injuries 

 and defects neglected for five years because of man-power shortages. Trees found 

 to be in such condition as to endanger the public should be removed, pruned, or 

 strengthened to eliminate hazards. In many communities a good start has been 

 made on constructive tree protection programs which should help limit the spread 

 of leaf diseases. 



The occurrence of broken tree limbs this year has resulted in numerous in- 

 quiries. Wind and rain storms have caused considerable damage of this type. 

 Also, in the course of reconverting housing and industrial activities for postwar 

 needs, there has been considerable cartage of relatively large, partly assembled 

 construction units throughout the State. The movement of such material is 

 ordinarily not sufficient to cause extensive breakage of roadside trees. However, 

 currently, extensive tree breakage is traceable to this source as well as to the in- 

 creasing movement of heavy road-construction machinery along highways. 



Diseases of Plants Caused by Soil-infesting Organisms, with Particular Atten- 

 tion to Control Measures. (W. L. Doran.) It was found that, in the absence of 

 fungicides, damping-off is much less severe if soils having a moisture content of 

 about 30 percent of the water-holding capacity at the time of seeding are not 

 watered for the first time until four or five days thereafter, i 



The use of fertilizers as carriers of soil fungicides, especially for the control of 

 damping-off, cabbage club-root, and soil-borne onion diseases, was further in- 

 vestigated. Organic fungicides used in this or the following project, and here- 

 after referred to by the trade names only, include tetramethyl-thiuram-disulfide 

 (Arasan, Thiosan, and Tuads); 2, 3-dichIoro-l, 4-naphthoquinone (Phygon); 

 tetrachloro-parabenzoquinone (Spergon); disodium ethylene bisdithiocarbamate 

 (Dithane D 14); ferric dimethyldithiocarbamate (Fermate); hydroxymercuri- 

 chlorophenol (Semesan); and zinc salt of 2, 4-trichlorophenol (Dow Seed Pro- 

 tectant No. 9.) 



Mercury salts, 0.2 gm. per square foot, applied to soil in the fertilizer, a 5-8-7 

 formula, did not control club-root of cabbage in the soils used as well as did hy- 

 drated lime. Best results on the basis of disease control and growth of plants 

 were secured with pyridylmercurichloride or ethyl mercury phosphate used in^a 

 limed soil. 



^The writer read a paper on "Control of Damping-off by a Delay in First Watering after Seed- 

 ing" at the December 1945 meeting of the American Phytopathological Society. An abstract will 

 appear in an early number of Phytopathology. 



