The following solutions were tested with respect to their fungicidal properties towards the “powdery,” conidial stage of S. Humuli on young hop-leaves in the greenhouse:
(1) Disodium arsenate, containing 0·096 per cent. As2O5 proved fungicidal and killed also patches of leaf-cells underlying the mildewpatches, but did not otherwise injure the leaf. A solution containing 0·02 per cent. As2O5 was fungicidal without killing any leaf-cells.
(2) Trisodium arsenate containing 0·077 per cent. As2O5 proved fungicidal.
(3) Dicalcium arsenate. containing 0·048 per cent. As2O5 proved fungicidal; containing 0·024 per cent. As2O5 the solution was apparently just fungicidal, but with 0·01 per cent. As2O5 the solution was practically non-fungicidal.
(4) Tricalcium arsenate containing 0·076 per cent. As2O5 is fungicidal; containing 0·02 per cent. As2O5 it possesses some fungicidal value, but with 0·01 per cent. As2O5 it is practically non-fungicidal.
(5) The following constituents of lime-sulphur wash proved nonfungicidal: calcium sulphate, sulphite, thiosulphate, hydroxyhydrosulphide.
(6) Calcium polysulphide, at a strength of 0·11 per cent., proved fungicidal.