182 INSKCTU'I ]>]•:«, FUNGICIDES, AND WEED KILLERS. 



these trees were influenced favourably, the buds were more vigorous, 

 fruits more numerous, growth more rapid, and that especially if the 

 treatment was combined with extra- racinary teeding, which finds many 

 partisans nowadays. The same observer has pointed out that kermes 

 such as DiaspisfaUax, Horv., of the pear-tree and Mytilaspis po7nori(m, 

 B., of the apple-tree were much less numerous and even disappeared 

 from the trees treated with green vitriol. It is the same as regards 

 the Gum and the Fiisicladium. 



Cryptogamic Diseases of Plants. — Attempts have been made to 

 combat by green vitriol and green vitriol bouillies diseases capable of 

 being restricted by blue vitriol and cupric bouillies. Green vitriol being 

 much cheaper than blue vitriol this substitution would have had great 

 pecuniary advantage. Unfortunately, the dose to use being ten times 

 larger to produce the same effect, this advantage disappeared, and the 

 use of green vitriol was restricted to the parts of the plant which bear 

 this treatment. Used in the same strength as blue vitriol in spraying 

 leaves attacked. by various diseases it does not produce the same salutary 

 effect. However, its action is not nil, and its stimulating power on the 

 vital functions of the plant causes the latter to suffer less from the 

 attacks of parasites, and often prevents their spreading. 



Potato Scab. — Nijpels found that green vitriol spread on potato 

 fields appreciably diminished the scab of the tubers without com- 

 pletely preventing it. 



Bacillary Gum of the Vine (Mai Nero). — The only remedy 

 capable of stopping the spreading of this disease is the radical 

 removal of all the diseased parts (Prillieux and Delacroix). The 

 wounds produced by pruning are coated with a concentrated solution of 

 green vitriol and afterwards covered with a mastic. Where contagion is 

 to be feared it suffices to coat the pruned sections to prevent the disease 

 penetrating by the wounds. Meunier practised winter coating in his 

 domain on every stock with a 50 per cent solution of gi een vitriol with 

 2 per cent of sulphuric acid. The effect was very satisfactory, the 

 parts which had previously perished were cured and contagion avoided. 



Bacterian Disease of the Mulberry. — Euiter recommends the green 

 vitriol treatment. As soon as a branch appears attacked it is cut off in the 

 healthy part a few centimetres below the diseased spot. The cut branches 

 are burned on the spot, then the pruned section is coated with a 45 per 

 cent solution of green vitriol. Trees so treated grow in the same year 

 of treatment vigorous buds and next year show no trace of the disease. 



Phytoj)hthorainfestans, De By. (potato disease). — Green vitriol ex- 

 erts an energetic action on the conidia of this fungus and a 1 per cent 

 solution should produce an eflect on the disease. Tried as substitutes 

 for cupric bouillies, 1 per cent solutions of green vitriol used in two 

 sprayings, the first on 18 June, the second on 15 July, produced 

 no improvement. Petermann obtained by this process the following 

 results : The plot treated gave 8-3 per cent of diseased tubers and 73 

 lb. of tubers. The check plot gave 11*3 per cent of diseased tubers 

 and 102 lb. of tubers. A strong manuring with green vitriol in the 

 spring will give such vigour to the potato plant that it will better 

 resist this disease. 



