The Rhizoctonia Damping-Off of Conifers 



27 



TABLE 7. Approximate Percentage of Damping-Off after Emergence in Relation 

 to Time of Sowing at the Keene Nursery during Fall and Spring, 1926-27 



* Average figure for check plats in soil-treatment experiments. 



It is evident that with Colorado spruce and white pine, losses were 

 practically uniform on beds sown either in the spring or in the fall. The 

 same is true of the beds of norway spruce at location A. At location B, 

 however, losses were high in the fall-sown beds but were considerably 

 lower than in those sown on May 6 and 7. High losses were noted also at 

 location D, but it should be stated that these beds were considerably behind 

 the other fall-sown beds in time of emergence. Losses on the red-pine 

 beds at location A were greatest in those sown on April 21, but were just 

 as high on the few fall-sown beds at location D. The fact that the most 

 severe damping-off occurred in the beds of red pine and norway spruce 

 which were sown in May does not necessarily indicate that the time of 

 sowing was the chief factor involved, for, as already pointed out, these 

 beds were situated in the sections of the nursery where the disease had 

 been most prevalent in years past. 



While the information obtained includes but one season's observations, 

 the data as a whole indicate that damping-off may occur to a serious 

 degree in fall-sown beds. The differences in prevalence of the disease at 

 the nursery under discussion are not shown to be definitely related to the 

 time of sowing. 



Soil treatments with chemicals 



Field tests with chemicals were begun at the Ithaca nursery in 1925 

 and continued on a more extensive scale at the Keene nursery during the 

 following two seasons. 



The twelve beds of the Ithaca nursery were used for a single experiment. 

 Each bed was divided into two sections 4 by 6 feet in size, thus providing 

 for three checks and three replicates of seven different treatments. Chemi- 

 cals were applied in solution, both directly after seeding and at various 

 times for several weeks thereafter. Following seeding operations the 

 beds were covered with burlap, which was removed as soon as emergence 

 began and was allowed to remain on top of the half-shade frames for a 



