•Ir> INSECTICIDES, Ef N(tK l DKn, AND \\i;i;i) KILI.ERS. 



mended by Dupouchel, Chauzit, and Dr. Debray, may be adopted. 

 Debray has, in fact, remarked that the phylloxera is killed more easily 

 during the active period of the vine, and that the duration of the submer- 

 sion can be reduced to eight days in September, while fifteen to twenty 

 days are required in October, and forty to sixty daj^s in winter. In 

 this connexion the underground irrigation described by Duponchel 

 produces the best effect. So that submersion may be complete and 

 efficacious, i.e. so that the water can penetrate 2 feet into the soil, it 

 requires 1000-1200 cubic metres of water per hectare, say 250-300 litres 

 (55-66 gallons) of water per stock. It is executed during dry periods, 

 when vegetation is not very active. It has been found, on the other 

 hand, that short, r3peated irrigations lasting forty-eight hours in 

 summer, especially if underground, are as injurious to the phylloxera 

 a3 long winter irrigations. Whilst even three days' immersion in 

 cold districts are injurious, underground irrigations of forty-eight 

 hours in the dry regions of the South have a favourable action on the 

 development of this plant. The causes, which in the exceptional con- 

 ditions of the French climate insure the prosperity of the vine and 

 the quality of French wines, are none other than the climate itself and 

 the method of culture applied, the hoeing of the soil. It creates on 

 the surface of the soil a shallow layer of friable earth, which by break- 

 ing the continuity of the capillaries arrests all evaporation from 

 below. The rain-water thus imprisoned in the soil without com- 

 munication with the exterior air constitutes that lasting store of 

 underground moisture, which can only be evaporated by the plant 

 which aspirates it by the roots and which loses it by the leaves. The 

 sap thus elaborated acquires that peculiar property of being specially 

 apt to develop fruits, whilst in moist districts submerged too often 

 the more aqueous sap perfectly produces herbaceous vegetation and 

 yields few grapes. To produce grapes of superior quality the fruits 

 must be developed in a warm medium, and the roots be in a moist 

 and warm medium. These essential conditions are awanting when 

 prolonged superficial submersion is practised, but are not greatly 

 affected by the underground irrigations recommended by Duponchel. 

 Superficial sprinkling of the soil never gives useful results as regards 

 grapes, l)ut develops branches full of leaves {pampres). The super- 

 ficial evaporation of the water so sprinkled by cooling the soil must 

 retard the ripening of the crop. Submersions would therefore in 

 general be rather prejulicial to the quality of the crop of a healthy 

 vine. As a curative agent, they produce, on the other hand, two 

 effects equally advantageous, they enable the vine to reconstitute its 

 radicular apparatus (root hairs) more or less atrophied by the gnawing 

 of this lous3. From this point of view, the irrigation of the vines 

 may be regarded as of practical utility, but it should be executed 

 with the greatest of precaution so as to modify as little as possible 

 the special conditions which insure the quality of the grape. A 

 sufficient imbibition must be created to be injurious to the phyl- 

 loxera, and favourable to the development of root filaments, avoiding 

 all loss of heat by superficial evaporation. These conditions are 

 realized by underground irrigation, especially if it be accompanied by 



