135 



GuENAux (G.). Comment lutter contre la Cochylis et I'Eud^mis. [The 

 Control of Clysia ambiguella and Pohjchrosis botrana.] — VieAgric. 

 et Riirale, Paris, vi, no. 50, 9th December 1916, pp. 430-434, 

 7 figs. 



As Chjsia ambiguella has two generations annually and Pohjchrosis 

 botrana three, the campaign against these insects has to be carried on 

 through all seasons. At the beginning of autumn, the larvae of the 

 second generation of C. ambiguella and the third generation of P. botrana 

 leave the ripe grapes and seek winter quarters, chiefly in the old bark 

 of the stock, a little distance above the ground, and here the larva 

 remains quiescent in its cocoon throughout the winter. During this 

 period, decortication is the method of control, and it seems scarcely 

 necessary to burn the old bark scraped off, as the pupae when dislodged 

 from their shelter fall exposed to the ground and die in enormous 

 numbers. Decortication is not necessary every year ; if a large area 

 be thus treated, one decortication should be sufficient for three years, 

 and whitewashing may take its place as an alternative measure. In cold 

 climates the branches should be washed over after decortication with 

 a 25 per cent, milk of lime, which completes the work of destruction and 

 at the same time forms an isolator. Although the value of decor- 

 tication is undoubted, scalding is a method that is often preferred 

 owing to its greater simplicity. The object of this treatment is to kill 

 all larvae or pupae by injecting water, as near as possible to boiling 

 point, under all the crevices in the bark. This should be done imme- 

 diately after the vintage, and should be carried out from the base of 

 the stock, advancing slowly upwards as far as the first buds, which 

 nmst not be touched. The best apparatus for the purpose is a boiler 

 provided with a length of rubber tubing ending in a bent jet. Owing 

 to the large quantity of water required, vaporisation has been tried 

 as a substitute ; this however requires a large and elaborate installation 

 and is onlv suitable for large areas. AMiitewashing the trunk with 

 insecticide solutions is a very favourable measure, but is less efficacious. 

 The follo^^ng formulae have given the best results : — (1) Heavy coal- 

 tar oil, 20 lb. ; carbon bisulphide, 10 lb. ; caustic soda, 2 lb. ; quick 

 lime, 40 lb. ; water, 20 gals. The lime is first slaked and mixed with 

 10 gallons of water. The oil and carbon bisulphide are mixed 

 separately and added very gradually to 10 gallons of water containing 

 the caustic soda in solution. This heavy emulsion is dropped into the 

 lime solution, stirring all the time. The mixture should not be prepared 

 more than 24 hours before use. (2) Heavy coal-tar oil, 20 lb. ; carbon 

 bisulphide, 10 lb. ; oleic acid from stearine factories, 4 lb. ; caustic 

 soda, 1 lb. ; water, 20 gals. The coal-tar oil, the oleic acid and the 

 carbon bisulphide are mixed together and jDOured into the water to 

 which the soda has been added, stirring all the time until a perfectly 

 homogeneous emulsion is obtained. Insecticide washings should not 

 be begun before the middle of March, as it is only when the sap begins to 

 rise that sufficient resistance is offered to the wash, which at other times 

 may be absorbed to the injury of the plant. 



Shelter-traps, made by wrapping bands of cloth round the trunks and 

 at the forks of the branches in early autumn, have been the means of 

 collecting many pupae in December ; these have the additional 

 advantage of preserving the parasites of the moths. 



