250 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



laise is recommended to overcome the fun^i of the same family as 

 oidium. Thus Selhy recommends houillie bordelaise to overcome: — 



Podospluera OxyacautJue, D. C, bhght which invades the ap]ile 

 and the cherry tree in America, but which in I'kirope only produces 

 the hawthorn blight. 



Spluerotheca Morsuvce. Berk et Courts (blight of the gooseberry), 

 which invades the fx'uits of this shrub in North America to such an 

 extent as to entirely destroy the crop. 



Spluetotheca pannosa, Lev. (mildew of the i-ose-bush and peach- 

 tree). — The reports of cures obtained by treatment with houillie 

 bordelaise are numerous. Ritzema Bos, Nijpels, and Speschneff 

 recommend this treatment to overcome this disease. Nijpels recom- 

 mends houillie bordelaise to overcome : — 



MicrosphcBra Grossularice, Wallr. (mildew of the gooseberry). — 

 However, houillie bordelaise will not act so efficiently and decisively 

 as sulphur at a high temperature, and cannot be advantageously used 

 to overcome blights. 



Hyjxnnyces perniciosus, Magnus (mole disease). — This disease 

 causes considerable damage in mushroom beds. Constantin and 

 Dufour submitted the spores of this injurious fungus to the action of 

 bouillie bordelaise and found that pi-olonged steeping in a 2 per cent 

 bouillie does them little harm, and it is only after three to seven days' 

 steeping that the spores are killed. 



Nectria ditisshna, Tul. (canker of the pear, apple, and beech trees) ; 

 Spceropsis malorum, Peck, (apple rot, pear rot, quince rot). — To 

 prevent these diseases Selby and Paddock recommend to scrape the 

 trunk of the trees, to clean the wounds, and to spray the whole tree 

 with bouillie bordelaise. This process has no action on already formed 

 cankers. Only their deep excision, followed by coating the living 

 wounds with a concentrated solution of green vitriol, acidulated by 

 sulphuric acid, can suppress them and cure the tree. 



Polystigma rubrum, D. C. (plum leaf blister). — Sorauer and 

 Nijpels recommend to prevent this disease to carefully burn the 

 dried leaves and to spray preventively with bouillie bordelaise on the 

 young spring leaves, or on the branches before the opening of the buds. 



Guignardia BidtreUi, Viala et Ravaz (black rot of grapes). — In 

 1887 trials were made at Ganges with blue vitriol. In spite of the 

 negative results of these trials the experiments were resumed the 

 following year at Aiguillon with bouillie bordelaise on a certain 

 number of black-rotted vines in 1887. After three sprayings, made 

 before the end of July, the stocks treated only had 14-24 per cent of 

 diseased grapes, whilst the untreated vines which surrounded them 

 had 95-99 per cent. Great publicity was given to these fortunate 

 results, so as to enable vine-growers to take in time the necessary 

 steps to prevent the extension of black rot around the hotbeds of in- 

 fection. Experience shows that bouillie bordelaise does not act on 

 black rot as on mildew. The summer spores of black rot being much 

 less sensitive to the action of cupric preparations than the zoospores 

 of mildew, it is necessary to use stronger bouillies and spray more 

 often. This fungus may develop, like mildew, with unheard-of rapidity. 



