428 Journal of Agricultural Research voi. v.no. w 



Mexico : 



On Quercus (?). — ^Jalapa, Charles L. Smith, No. 146 Central American Firngi, in 

 1894 (No. 4709, Herb. Lloyd). 



From the foregoing data it will be noted that the following trees are 

 attacked by the disease caused by 5. subpieatum: Q. allba, Q. coccinea, 

 Q. lyrata, 0. marilandica, Q. michauxii, 0. minor, Q. palustris, Q. phellos, 

 Q. prinus, Q. rubra, Q. texana, Q. velutina, Q. virginiana, Quercus spp. 

 and Liquidamhar styracifiua ( ?) . 



CONTROL OF THE HONEYCOMB HEART-ROT CAUSED BY STEREUM 

 SUBPILEATUM 



The honeycomb heart-rot caused by 5. subpileatum is one of several 

 important heart-rots of oaks in the United States. Suggestions made 

 for its control will apply more or less to all of these. The fact that 

 apparently oaks of all ages are susceptible to this rot, provided they 

 are old enough to have formed heart wood, must be taken into consid- 

 eration when discussing methods of control. The only practicable 

 method of control known which can be applied to the forest as a whole 

 is to prevent, so far as possible, the infection of the trees. This can 

 be done (i) by eliminating, so far as possible, all forest fires, since they 

 produce wounds on the butts of the trees through which the fungus 

 enters; (2) by preventing the formation of the fruiting bodies (sporo- 

 phores) of the fungus which produce the spores. These spores are the 

 direct agents for infecting the trees through dead branches and fire 

 scars. 



The only method at present known by which the development of the 

 sporophores of this fungus can be prevented is the destruction of all 

 diseased timber which contains this rot. In lumbering tracts of oak 

 all unsound or diseased trees should be cut, the parts that can be used 

 removed, and the cull logs and dead trees burned, since this fungus 

 fruits most abundantly on old logs and on dead fallen timber. Many 

 trees under the present methods of lumbering are left standing because 

 they have heart-rot in the butt. If cut down, these trees would usu- 

 ally be found to contain enough lumber to pay for the cost of opera- 

 tion. Such a procedure will lead to a better and closer utilization of 

 our gradually decreasing supply of oak and insure a healthier future 

 forest. 



Special emphasis should be placed on the fact that the rot produced 

 by S. subpileatum can continue to grow in a tree after it is felled, and 

 that every cull butt, log, or tree left on the ground in a lumbering oper- 

 ation will later bear an enormous number of sporophores of this fun- 

 gus which will discharge annually millions of spores for many years. 

 In the interest of the health of the future forest, it is therefore of the 

 utmost importance that all of these cull logs and trees be destroyed. 



