ANNUAL REPORT, 1947-48 21 



Thirteen progress reports (mimeographed) and six press releases were sent 

 out during the year. 



Cytospora Disease of Spruces. A common malady of ornamental spruces is a 

 canker disease which attacks twigs and branches. In previous reports the cause 

 of the disease was identified tentatively as the fungus Cytospora Kunzei Sacc. 

 Lacking the identification of the causal fungus in its perfect stage on spruce, the 

 disease was called, commonly, the "Cytospora disease" or "Cytospora canker." 



In April 1947, a fungus identified as Valsa Kunzei Fr. was found associated 

 with cankers on twigs and branches of Norwa}^ spruce and Colorado blue spruce. 

 This fungus, believed to be the perfect stage of the aforementioned Cytospora, 

 was described in detail, and a study was made of the growth and appearance on 

 artificial culture media and on sterilized host tissue. Inoculations on young Nor- 

 way spruce trees with Valsa Kunzei resulted in cankers and the death of some 

 of the inoculated branches. 



The Valsa stage may be involved in the natural spread of the disease by means 

 of wind-blown ascospores, and further investigations into that possibility are 

 needed. Also, a more intimate knowledge of factors predisposing spruces to 

 the disease and avenues of host infection by the fungus are to be desired as pre- 

 requisites to an attempt to achieve effective control. 



Other Tree Problems. Forty-eight diseases of twenty-three species of trees, 

 including seven diseases of elm, were identified from more than 1500 specimens 

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

 reported from one additional municipality in the State. Verticillium sp. was 

 isolated from several species of woody plants. 



Winier injury to trees and co evergreens in particular was extensive this year. 

 Later, during the extended period of wet weather at the time tender foliage was 

 developing, conditions were ideal for infection of leaves by fungi. Elms, maples, 

 sycamores, oaks, and ashes were among trees on which foliage was seriously 

 affected and partially lost in early summer because of leaf diseases. Also, heavy- 

 infection of leaves by the black spot fungus indicates that additional loss of elm 

 leaves may be expected by midsummer. 



Two other tree disease problems have occasioned increasing numbers of in- 

 quiries in recent years. The death of individual branches and limbs in maples, 

 leaving characteristic reddened or bronzed flags presents a problem which calls 

 for study; and the dying of oaks lacks specific explanation. In limited studies, 

 a combination of circumstances, including the preliminary weakening of the 

 oaks bj' the defoliating gypsy moth, appears to be a logical explanation of the 

 heavy mortality among these trees. 



Damping-off and Growth of Seedlings and Cuttings of Woody Plants as 

 Affected by Soil Treatments and Modifications of Environment. (W. L. Doran.) 

 Work was continued on the effects of fungicides applied as powder-dips to cut- 

 tings immediately after treatment with a root-inducing substance, usually 

 indolebutyric acid, applied by the solution-immersion method. 



The following fungicides thus used were harmless to the cuttings of these 

 species: Spergon (tetrachloro-parabenzoquinone) with Canada hemlock. Genista 

 pilosa, and Juniperus squamata Meyeri; Phygon (2, 3-dichloro-l, 4 naphtho- 

 quinone) with Canada hemlock and Genista pilosa: morpholine thiuram disulfide 

 with Carolina hemlock; zinc ethylene bisdithiocarbamate with red cedar; and a 

 zinc dimethyl dithiocarbamate-cyclohexamine with Chinese juniper. 



