The Rhizoctonia Damping-Off of Conifers 



37 



It is apparent, then, that the liquid treatments were equally effective in 

 controlling damping-off, even where very small amounts of the mercury 

 materials were used and under conditions in which severe damping-off 

 occurred in the check plats (figure 2) . With the exception of an occasional 



1600 

 1400 

 1200 



/poo 



80C 

 600 

 400 

 ZOO 



I 



/ 2 3 4 5 & 7 3 9 /O II /Z CM 

 EXPERIMENT A 



EXPERIMENT B 



Figure 2. 



The numbers below the columns refer to the treatment numbers given in table 10 



FINAL STAND OF RED-PINE SEEDLINGS IN PLATS TREATED WITH LIQUID 

 APPLICATIONS OF CHEMICALS 



group of slightly stunted seedlings in several plats treated with the stronger 

 applications, no evidence of chemical injury could be detected (Plate IV, 

 1 and 2, and Plate V, 1). 



In experiment C, sulfuric acid was less effective than aluminum sulfate 

 in controlling the disease. The results with the weaker acid treatment 

 were not significantly different from those obtained from the check plats. 



Red pine — Treatments with dry chemicals. Preliminary experiments 

 were conducted at the Keene nursery in 1926 with applications of finely 

 divided copper carbonate and Bayer dusts 1-8, 101, and 112, at the rate of 

 4 and 8 grams per square foot. Favorable results were obtained on a small 

 scale with the mercury dust, while the copper carbonate caused severe 

 injury. Bayer dust, Dipdust, and copper carbonate were similarly used 

 on fall-sown beds of the same year. The copper carbonate (1, 2, and 3 

 grams per square foot) did not control the disease in the smaller amounts 

 and caused injury in the larger applications. The mercury dusts (3 and 6 

 grams per square foot) were only partially effective against the disease. 



