COPPER SULPHATE (BLUE VITRIOL). 211 



vitriol. In the same way caterpillars are not inconvenienced by con- 

 tact with blue vitrioi solutions. Dufour found that a 10 pei' cent 

 solution did uot inco:nmode the catei pill ir of the Gochylis of the vine. 

 Mouillefert i nmersed vine roots beariiio; numerous phylloxera for three 

 days in a saturated solution of blue vitriol and still found many livmg 

 msects ; it was only after five days' immersion that all the phylloxera 

 died. The great resist ince of this louse is, therefore, the cause of the 

 bad results obtained with the different processes of destruction recom- 

 mended in 1872 and submitted to the control of a special commission. 

 If blue vitriol cannot bs regarded as a poison by contact, it, however, 

 becomes poisonous when absorbed by the leaves, and the favourable 

 results obtained by the b millie bordeliise ad nit of no doubt in the 

 matter. Besides, insects avoid gnawing the organs touched with blue 

 vitriol, and are thus removed by spraying. Targioni Tozzetti, having 

 steeped potatoes in a solution of blue vitriol, found that the larvas of 

 the E later ides did not touch them. la this way Angel i met with 

 complete success against the phylloxera in the island of Elba, by in- 

 jesting blue vitriol into the diseised stocks. Dying vines revived by 

 this treatment, for the phylloxera disappear .^d from the stocks treated. 



Use of Blue Vitrior to Kill Weeds.— Amongst chemical weed 

 killers, blue vitriol is one of the most efficient. Bonnet, a vine-grower, 

 found it out fortuitousiy. He observed that the mustard whicii grew 

 amongst the vines was destroyed by blue vitriol, whilst oats, growing 

 in the same condition, were immune. Trials made by Benard and 

 Brandin showed that a 5-10 per cent solutio i of blue vitriol disorganized 

 the cruciferae growing amongst cereals without injuring the latter. Its 

 disorganizing action is more powerful than that of green vitriol. 

 Whilst it requires 15-20 per cent of this latter salt, 4-5 per cent of blue 

 vitriol suffices to produce the same effect, at the rate ot 41-88 gallon- per 

 acre (Dussere). It is better to use mixtures of blue vitriol and nitrate 

 of soda as weed killers. The yo mg plants are destroyed by a mixture 

 of 2 per cent of blue vitriol and 10 per cent of nitrate of soda, sprayed 

 at the rate of 8-10 hectolitres per hectare (70-4-88 gallons per acre). 



Use to Destroy Parasitic P. ants. — Cuscuta minor, D. G. (small 

 dodder of the lucerne and clovar) ; Cuscuta densijlora, Willm (dodder 

 of flax) ; Cuscuta major, D. C. (large dodder of the hop and hemp 

 plant). — Blue vitriol kills dodder in mich s nailer doses than green 

 vitriol. From 2-5 per cent solutions of blue vitriol suffice. Their 

 method of use is the same as for green vitriol. 



Orobanche ramosa (branchy orobanche of hemp and tobacco) ; 

 Orobanche minor (clover orobanche). — Gennadius advises to destroy 

 these parasites by a 5 per cent solution of blue vitriol, which destroys 

 their seeds. 



Use against Mosses and Lichens. — Coating with a mixture of 

 6 per cent of blue vitriol and 2 per cent of sulphuric acid readily de- 

 stroys the mosses and lichens which grow on the trunks of trees. 



Use ag-ainst Cryptogamic Diseases of Plants. —Phytoj)hthora 

 infedans, De By. (potato disease). — The analogy between the Phyto- 

 phthora and the P.ronospora, combated with so much success by 

 copper salts, led to the belief of an analogous efficiency of these in 



