Feb., 1926] PROGRESS OF AGRICULTURAL EXPERIMENTS 



9 



beans, tomatoes and radishes, which have been mostly used, injury is Hkely to 

 result from the use of an alkaline Bordeaux mixture. The injury when pro- 

 duced only occurs on the young tender leaves and is not increased when the 

 sprayed plants are wet with dew during the night following the application of 

 the mixture. The experiments so far carried out indicate that in the case of 

 plants not sensitive to copper an alkahne Bordeaux mixture may cause injury 

 to the young leaves when a neutral mixture will not. In the case of plants 

 sensitive to copper, as the peach, alkaline washes are more injurious to young 

 foliage than neutral mixtures. 



Toxicity of Fungicides to Parasitic Fungi. 



When lead arsenate is added to Ume-sulphur solution, double decomposition 

 occurs, and soluble arsenic is found in solution, whereas when calcium arsenate 

 is used decomposition does not occur. It is generally considered that the 

 addition of lead arsenate increases the toxicity of lime-sulphur solution, but the 

 situation regarding calcium arsenate has not been clear. Accordingly, W. L. 

 Doran (Botany) has studied the effect of an addition of lead arsenate, calcium 

 arsenate and arsenious oxide in solution, on the toxicity of lime-sulphur to the 

 spores of the apple scab fungus. The results obtained as will be seen from a con- 

 sideration of the data presented in Table I fully corroborate the view that lead 

 arsenate increases the toxicity of lime-sulphur and that the presence of soluble 

 arsenic sufficiently accounts for the increased toxicity noted. 



Table I. — Effect of the addition of lead arsenate, calcium arsenate, and arsenious oxide on the 



toxicity of lime-sulphur. 



It has also been found that the toxicity of lime-sulphur solution may be 

 greatly increased by the addition of copper sulphate. The results of experi- 

 ments with the spores of the apple scab fungus are given in Table II: 



Table II. — Effect of copper sulphate gn the toxicity of lime-sulphur solution. 



