522 



which mixture is the best. The value of any of them depends on the 

 quantity of sohible copper present to a certain extent, and provided 

 there be sufficient, there is no proof that the alkahne mixtures, though 

 containing less copper in solution at the moment of use, are any less 

 efficacious than the acid containing approximately five times as much. 

 Eavaz states that three parts of copper sulphate in a million of water 

 are sufficient to stop the germination of the mildew spores, and thus 

 the weakest Bordeaux mixture is 75 times stronger than necessary, 

 if this be true. The autho.rs conclude by saying that there is no 

 distinction to be made between the various Bordeaux mixtures ; 

 either acid or alkaline should have the same value. 



Semichon (L.). Nouveau proc6d6 de traitement des insectes et des 

 cryptogames par I'eau chaude et les bouillies chaudes. [A new 

 method of insect and cryptogam control by hot water and hot 

 spray mixtures.] — Rev. Vitic, Paris, xlii, nos. 1089 & 1090, 13th 

 & 2()th May 1915, pp. 398-405 & 424-425. 



The bulk of the information given in this paper has been taken 

 from a previous article [see this Review, Ser. A, ii, p. 685]. The larvae 

 of Arctia caja and Haltica ampelophaga are also killed by hot water 

 at temperatures between 122° and 150° F., which destroys the eggs 

 of these two species and of Sparganothis piUeriana, as well as of 

 those of Clysia and Polychrosis. Vine pests may be treated with 

 hot water at any time during the three weeks which elapse 

 between the date of oviposition and that on which the larvae take 

 shelter within the injured plants, whereas arsenicals are efficient for 

 a period of about five days only. If hatching is spread over three or 

 four weeks, one careful application of hot water, or tM'O at most, will 

 allow of absolute theoretical control ; the proportion of survivors 

 found in practice depends simply on the thoroughness of the treatment. 

 Hot water is also effective against Tetranychvs telarius, Eriophyes 

 (Phytoptns) vitis, and probably Coccids also. Treatment should only 

 be carried out in dry weather, not after rain or dew. Stress is laid on 

 the proper method of filling a knapsack sprayer (of 26J pints capacity) 

 when a hot spray solution is used instead of plain hot water. In the 

 former case, 8f pints of treble strength solution (cold) is poured into 

 the container and the latter is then filled by adding 17| pints of boiling 

 water, briskly stirring the while. The operator should apply the 

 spray at once. The degree of heat mentioned increases the efficiency 

 of the sprays used against the vine mildew {Plasmopora viticola), 

 black-rot {Guignanlia bichcelli) and the Phytophthora of the potato and 

 of the tomato. 



Eavaz (L.). Traitement contra les insectes. [Insect pest control.]— 

 Progres Agric. Vitic, Monfjjellier, Ixiii (32nd year), no. 20, 16th 

 May 1915, pp. 457-461. 



Referring to M. Semichon's hot water method of pest control [see 

 this Revieiv, Ser. A, ii. p. 685], an account is given of the use of steam 

 by M. Bonneau in Anjou some years ago, the experiments being 



