. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. 14 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. cases. It may furthermore be that in other cases the disinfectant had a stimulating effect, resulting in better germination in the treated plats, entirely aside from that resulting from parasite control. The number of disinfectant methods which concurred in giving apparent increases in germination, however, makes it seem reasonably cer- tain that no great part of the increase was due to this stimulation. In addition to the different d
. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. 14 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. cases. It may furthermore be that in other cases the disinfectant had a stimulating effect, resulting in better germination in the treated plats, entirely aside from that resulting from parasite control. The number of disinfectant methods which concurred in giving apparent increases in germination, however, makes it seem reasonably cer- tain that no great part of the increase was due to this stimulation. In addition to the different disinfectants shown in the table, mer- curic chlorid, heat, hydrochloric acid, nitric acid, and ammonia all apparently resulted in approximately the same increases of germina- tion in tests at the Bessey Nursery as the sulphuric acid which was used as the standard for comparison in most of the series. Relative emergence in treated and untreated plats, as well as damping-off. Fig. 7.—A clean-killed area in a bed of Pinas ponder osa, caused by Corticium vagum. Inside a 12-inch circle at the center of this "patch" no seedlings appeared. It will be noted that the weeds as well as the pines have been killed with the exception of Salsola tragus. loss after the seedlings appeared, was determined at two nurseries in addition to those given in the table. The results at these nurseries in general confirmed those at the five nurseries covered by the table in showing lower emergence in the controls. Although it is impossible to draw positive conclusions, some idea of the seriousness of losses before the appearance of the seedlings above ground can be obtained by studying the data in Table I. The fact that such losses appear considerable, sometimes exceeding the losses from the damp- ing-off that occurs after emergence, is believed to explain the com- mon failure to secure satisfactory results from control measures taken after the seedlings have come up and the disease has become
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