242 MASS. EXPERIMENT STATION BULLETIN 271 



crops on the tobacco which followed them disappeared after the first year 

 or two of tobacco. 



Assuming, for hypothetical purposes, that brown root-rot is associated 

 with certain soil microorganisms, which may result in a deficiency of nitro- 

 gen and (or) the formation of toxic substances in the soil, it is con- 

 ceivably possible that certain inorganic salts applied to soil might inhibit 

 i-uch microorganisms or might inactivate, chemically, such toxic substances. 

 Copper oxide, copper sulfate, copper acetate, lead sulfate, or lead acetate 

 were applied in varying amounts to brown root-rot soil (timothy sod), and 

 in it tobacco was grown. These salts of copper and lead, in the amounts 

 used, were all somewhat toxic to tobacco plants. 



Since brown root-rot is worse in some soils than in others, under the 

 same cropping system, work is now in progress with the object of finding 

 some of the relations between brown root-rot and certain characteristics 

 of the soil, including total nitrogen, P2O3, organic matter, soluble iron 

 and aluminum, mechanical condition, and water-holding capacity. The 

 chemical work involved is being done in the Fertilizer Control Laboratory, 

 and tobacco is being grown in all (12) soils. 



A Seedbed and Field Survey of Tobacco Diseases in Massachusetts. 

 (W. H. Davis, O. C. Boyd, and W. L. Doran). In a tobacco disease survey 

 of the State, 50 seedbeds and about 100 representative fields were inspect- 

 ed. The results may be briefly summarized as follows: 



Seedbed Survey 



(1) The soil was sterilized in 25 per cent of the seedbeds. 



(2) Twenty per cent of the seedbeds were sprayed or dusted; this 

 practice was followed by nearly everyone planting ten acres or more. 



(3) Growers who sterilized their seedbeds were rewarded with superior 

 plants and fewer losses in the crop from wildfire, mosaic and other dis- 

 eases. 



(4) In one instance where a few plants from a bed infected with wild- 

 fire were transplanted to a fourteen-acre field, 30 per cent of the plants 

 in the field became infected, causing appreciable loss at harvest. 



(5) Growers who have their seed "blown" believed it to be a good 

 investment, permitting use of less seed and insuring better and earlier 

 plants. 



Field Survey 



(1) Wildfire was found in all fields inspected, except ten, with losses 

 from a trace to 20 per cent. 



(2) Angular leaf-spot caused by a bacterium {B. angulatum) and new 

 to most of the growers was located throughout the area. 



(3) Mosaic or calico was the most prevalent disease, as it occurred in 

 nearly every field. 



Onion Diseases and Use of Fungicides on Onions. (AV. L. Doran). In 

 cooperation with A. I. Bourne, systematic observations were again made 

 in many onion fields, and for the second year spraying and dusting ex- 

 periments were conducted. There was neither blast nor mildew here 

 in 1930. 



Yields were not aflfected by copper lime dust; but were increased 13 or 

 16 per cent by Bordeaux mixture 4-4-50, applied 4 or 6 times, respectively, 

 and 17 or 24 per cent by Bordeaux mixture 8-4-50, applied 3 times or 

 twice, respectively. 



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