1^87.] Pylloxera Vastatrix at the Cape. 61 



Incomplete as they are, they unfortunately lead to a most calami- 

 tous conclusion, viz., that the spread of the phylloxera at the Cape, if 

 left unchecked, is more rapid than in any other country where the 

 insect has established its footing. 



MEASURES TAKEN FOB THE DESTETJCTION OF THE INSECT. 



The Commission could not hesitate with regard to the destructive 

 agents to be employed. Following the recommendation of the Com- 

 mission Superieure du Phylloxera, and a destructive, not a curative agent 

 being required, they decided on using Bisulphide of Carbon (C.S.^) 

 The quantity of water available for the use of Sulf o Carbonates being 

 here either insufficient or not easily attainable. 



I applied at first 300 grammes of Bisulphide per square metre, in 

 three treatments of 100 grammes each, and with nine holes of injec- 

 tion, but further experiments have shown that 200 grammes per 

 square metre were quite sufficient. 



The submersioc system has been also resorted to. It being found 

 that a part of Mr. S. Kotze's vineyard could be submerged from the 

 water of the Liesbeek Kiver, the Government authorised the throwing 

 of a dam to put to the test the submersion system, and a surface of 

 some nine acres, divided in two dams, was kept under water for a 

 period of sixty days ; the ground which was thrown up for embank- 

 ments had previously been treated with Bisulphide. 



That period of sixty days was not decided upon at random. Owing 

 to the numerous fatty tubercles which cover its body, the phylloxera 

 is not easily wetted ; it can be immersed in a liquid without being in 

 direct contact with it, being enveloped in air. Dr. Maxime Cornu has 

 also shown that the new layer which separates the old bark from the 

 new (the very dry exterior part of the new suler) is damped with very 

 great difficulty only ; and a long period of submersion is therefore 

 required to change the conditions in which this suberose layer remains 

 dry, and meanwhile affords means of subsistence to the insect. 



Professor Balbiani has shown also in his admirable researches on 

 the structure and vitality of the Qg^ of the phylloxera, that when 

 immersed in water, at the time the embryo had only begun to appear, 

 or was but little developed, they accomplished their evolution until 

 they were hatched, and that if the embryo was already well developed, 

 the young often died in the e^^, but only after a long stay under 

 water. 



A submersion of forty days has been found sufficient in Europe, 

 but it has to be repeated every two years, and Balbiani ascribes that 

 necessity to the escape of a few eggs. 



The endeavour of the Phylloxera Commission has been to leave as 

 little as possible to chance, and after a submersion of sixty days from 

 the 1st of September — that is to say at about the time of renewal of 

 activity in the part of the insect — I have vainly sought for a phyl- 

 loxera on the roots of the few vines which have survived that long 

 stay under water. 



The importance of this experiment at the Cape is very great. Many 

 farmers would be able, were the contagion to spread, to submerge 

 parts of their vineyards at a comparatively small expense now that a 

 trial has been made which, up to date, has given satisfactory results. 



