36 PROTECTION OF PLANTS — 1924-25 



It will be noticed that dust treatments were best for the season as far as 

 smut control is concerned, the results being: 



Nickel sulphide 0.8% smut. 



Nickel carbonate (H. F. G.) 1.66% 



Nickel hj'-drate (by caustic ppt'n.) 1.7% 



Coppfei" carbonate 2.1% 



Nickel hydrate (by lime pptn.) 2.5% 



The checks (inoculated with both smuts but untreated) varied in smut 

 count from 55.4 to 60 percent. It is thus obvious that with hull-less oats 

 nickel salt dusts were very efficacious. The nickel dusts were placed at my 

 disposal by Mr. Geo. Sanders of the Deloro Chemical Company, and were 

 used at the rate of 2 ozs. per bushel of grain. 



1. Dickson, B.T., R. Summberby and J. G. Coulson. 



Experiments in the control of oat smut. 

 Quebec Soc. Prot. Plants Kept. 16: 102-105, 1923. 

 • 



2. Dickson, B.T. Oat smut control experiments in 1923. 



• Quebec Society Prot. Plants Kept. 16: 77-79, 1924. 



MOSAIC OF RHUBARB. 

 By B. T. Dickson. 



In Ju'y 1922 the writer observed three rhubarl) plants in a market garden 

 patch near Montreal, which appeared to be mosaic diseased. The plants were 

 dwarfed sufficiently to be noticeable and were definitely paler in general color. 

 The leaf blades were mottled and somewhat savoyed intervenally. Discolored 

 longitudinal areas on the petioles were especially prominent in the reddest plant. 



In the spring of 1923 the number of diseased plants had increased to eight 

 and the newly diseased plants were alongside those found in 1922. The latter 

 were still further dwarfed, were more mottled and the general chlorophyll con- 

 tent more reduced. 



In the spring of 1924 there was a further increase in diseased plants and 

 accentuation of symptoms of previously noted cases. This year aphids were 

 plentiful on the rhubarb. 



Mr. Vanterpool inspected the patch early this season (1925) and found 

 60% of the plants infected. Dwarfing and chlorosis were very marked. Many 

 leaves were pale green with a few dark green patches here and there on the leaf 

 blade (fig. 1). Inspection for Rumex spp. with mosaic in the vicinity has been 

 negative in result. 



