224 INSECTICIDES, FrNGICIDES, AND WEED KILLERS. 



uredospores, thou^^h much less resistant than the spores of most fungi, 

 are yet destroyed by a 0"124 per cent sokition of blue vitriol ; their 

 sensitiveness to this salt begins at the dose of 0-00124 ; at 0'0124 per 

 cent germination is prevented. Hitchcock and Carleton found a 0*1 

 per cent solution prevented their germination without killing the spores. 

 H. de Vilmorin and F. Douillet found that plants of white March 

 Chiddam wheat, treated several times with blue vitriol sprays and 

 afterwards conveyed close to mildewed wheat, were not attacked, 

 whilst in the same conditions untreated plants were invaded. But thi& 

 treatment, difficult even when the wheat is in the blade, becomes im- 

 practicable when it is in the ear. It is owing to this difficulty that 

 this process has miscarried, although it has been found efficient in ex- 

 periments on the large scale in Australia, and by Leon Noiret in the 

 Cote d'Or. The dose required to kill, uredospores is much greater than 

 to destroy the zoospores of mildew of the vine, and it is surprising 

 that spraying has such perfect results. In our opinion, blue vitriol 

 would act in this case more especially as a stimulant, producing more 

 active and vigorous growth, enabling the plant to oppose a greater 

 resistance to invasion by this fungus, and thus to acquire a sort of 

 immunity. 



Helminthosporium graminaum, Eriks. (browning of barley). — 

 Kolpaon Eaon insists that Kuhn's process is an excellent means of 

 preventing this disease. 



ClavicejJS jmrpurea (ergot). — The conidia of this fungus do not 

 develop in a solution of blue vitriol of 0-0124 per cent. 



Dematojyhora necatrix (root rot of the vine). — Dufour recommends 

 blue vitriol to prevent this disease. When the roots are completely in- 

 vaded by the mycelium the plant is condemned, and ought to be de- 

 stroyed, the more so as the organs of propagation, the conidiophores, 

 charged with conidia, appear to develop, especially after the death of the 

 tree. By tearing up the tree and carefully exterminating the debris of 

 the roots and the ropes, the propagation of the disease is prevented. 

 To destroy the spores, or the mycelium, of which the soil may retain a 

 fraction, the latter is watered with a 3 per cent solution of blue vitriol. 

 Before planting new vines 1-2 litres of this same solution is poured 

 into the holes. Within a radius of 2-3 rows the stocks already 

 attacked or not are stripped in the spring and freely watered with 

 this solution ; 100-150 grammes of blue vitriol in powder may likewise 

 l)e spread per stock. The result is not always complete and visible the 

 first year, and it is sometimes necessary to repeat this treatment two 

 years running ; the results obtained in these conditions are, however, 

 very positive. 



Guignardia Bidwellia, Viala et Eavaz (black rot of the vine). — 

 From the first appearance of this disease, when it was found that it 

 did not appear at first on the fruit but only the leaves, which then 

 became hotbeds of infection for the grapes, attempts were made to 

 stop its evolution by repeated sprayings of blue vitriol. The experi- 

 ments made at Ganges were not very satisfactory, whilst bouillie 

 bordelaise later on gave the most perfect results. Eathey and Havelka 

 have proved that the spores are killed after thirty hours' steeping in a. 



