319 



has asserted that this scale will not survive burying in the ground, 

 although there are undoubtedly species which are not affected by such 

 treatment. The matter was put to the proof by planting a large number 

 of sets of several varieties and, two months after planting, living scales 

 were still to be found on the sets. There may possibly have been a 

 second generation, though the number was markedly less than when 

 the sets were planted, and it is at least clear that burial in the soil 

 is not favourable to the scale. Three and a half months after they 

 were put in the ground numbers of full-grown scales were found on 

 certain of the sets, while others were free, possibly owing to the large 

 development of the leaf sheaths. The general result of this series of 

 experiments, which are set out in great detail, w^as that five months 

 after planting almost every plant of the many varieties tried showed the 

 presence of scale. The insects were, however, not numerous and in a 

 certain number of cases entirely absent ; young larvae were hardly ever 

 found . It is noted as a remarkable fact that the scale was never found on 

 that part of the stock which was above ground. It was further observed 

 that there was more scale on those plants raised from sets from which 

 the old leaf sheath had not been removed. Comparison of plan- 

 tations leads to the belief that the nature of the soil is an important 

 factor, the pest being more prevalent on light soils than on heavy, 

 and that certain standard varieties of cane are less affected than others. 

 The author regards it as clearly proven that the infection can be carried 

 by the sets and that, in his experiments, the question of possible wind 

 carriage does not arise, for no scales were found in the control (originally 

 scale free) rows of plants. This being the case, the question arises as 

 to how infection may be avoided and how the sets may be freed from 

 scale. An emulsion of 12 per cent, carbohneum and another of 40 per 

 cent, petroleum with soap and water was tried, and it was found that 

 either was sufficient to kill all scales on the sets, and prolonged and 

 careful trials showed that the carbohneum emulsion strong enough to 

 kill the scale had no effect on the sets themselves, but that petroleum 

 was not satisfactory in this respect. The sets were dipped in the 

 emulsion for 10 to 15 seconds in wooden tanks and then set aside to 

 drain thoroughly ; it was found necessary to keep the emulsion in the 

 tank incessantly stirred, otherwise drops of pure carbohneum separated 

 out and damaged the sets ; the emulsion, even at 15 per cent., did not 

 harm the hands and arms of labourers employed in dipping, and it 

 further served as a most excellent fungicide against the pineapple 

 fungus, Thielaviopsis, rendering the use of Bordeaux mixture un- 

 necessary. The results of lengthy comparative trials of carbohneum, 

 tar and Bordeaux mixture are given, from which it is clear that certain 

 varieties will not bear the carbohneum treatment at all and that others 

 bear it well, especially the variety described as 247 B., and even the 

 10 per cent, emulsion seemed effective ; petroleimi even at 30 per cent, 

 killed over one-third of the sets ; Bordeaux mixture is absolutely 

 useless against the scale as a contact poison, but scarcely a plant that 

 had been treated with 2 per cent, milk of lime showed primar}^ scale 

 infection ; wiping with a rag soaked in paraffin is a common method 

 and is apparently successful, but many young scales near the " eyes " 

 of the set escape, and this is precisely that stage which best resists 

 burial in the soil. The objection to the wiping method is that it is 

 costly in time and labour and is hable to be carried out perfunctorily 



