22 MASS. EXPERhMENT STATION BULLETIN 368 



1. Removal and burning of all dead, wind- or storm-damaged, diseased, and 

 insect-infested parts of affected trees. 



2. Sealing of all wounds with a wound paint after making a clean cut on the 

 wood surface. 



3. Spraying in order to control fungus and insect pests. 



4. Watering and feeding according to apparent needs. 



With due allowance for the interpretation and execution of directions, reports 

 from individuals who have tried these suggestions indicate that treatment has 

 achieved a measure of success. However, after so limited a time as two years, 

 or less in some cases, it is not possible to state definitely whether more or less 

 regular attention must be given to the building up of the general health of affected 

 trees. The continued presence of the fungus responsible for the trouble would 

 appear to indicate that such regular attention to tree vigor is essential for con- 

 tinued freedom from renewed wilt attacks. To owners of valuable trees, annual 

 attention as a preventive is a legitimate and profitable investment if annual 

 dividends in tree vigor and freedom from the disease are returned. 



SUMMARY 



1. A wilt disease of elm associated with a fungus belonging to the genus 

 Cephalosporium Corda has become widespread in Massachusetts. The disease 

 itself is a typical vascular mycosis which cannot be distinguished from other 

 vascular diseases of elm, except by identification of the causal fungus from cul- 

 tural studies of tissue plancings in the laboratory. Under experimental condi- 

 tions, the organism frequently reacts similarly to Ceratostomella ulmi (Schwarz) 

 Buisman, which causes the Dutch elm disease. Infection early in the growing 

 season is apparently more destructive than infection late in the summer or fall. 



2. The external symptoms of the disease are typical of die-back diseases, and 

 the internal symptoms include brown streaks in the wood. 



3. Aerial nncelium will grow on infected twigs under certain conditions. 



4. Measurements of the spores and of vessels and tracheids, and microscopic 

 studies of the fungus in the tissue, support the hypothesis that the fungus may 

 be spread by means of spores within the tree. 



5. Spores were found to germinate most readily on potato dextrose agar, in 

 darkness, and in a moist atmosphere. 



6. The thermal death point of the causal fungus has been placed between 

 75° and 80° C, and freezing was not found to exert any influence on the viability 

 of the spores. 



7. Sporogenesis is typical of the genus Cephalosporium as described by 

 Buchanan. 



8. Inoculations were made from single-spore colonies in stems and leaves of 

 elm trees of the following species and varieties: U. americana L., U. iniicricana L. 

 {war. ascendens), U. campestris L., U. glabra L. vav. fasttgiata Rchd., U. parvi- 



folia Jac(i., and U. pumila L. 



9. Infection followed inoculation of freshly wounded leavt-s in all cases; and 

 all the trees, with the exception of U. glabra L. var. fastigiata Rehd., were in- 

 fected by the twig inoculations in fresh wounds. In nature, comparable fresh 

 injuries by insects would serve readily as infection courts if the insects them- 

 selves were the principal vectors; and the reports by Becker of a native elm bark 

 beetle invading living cambium may prove to have particular significance in 

 connection with the spread of the Cephalosporium fungus. 



