I have been struck by the fact that the amount of gum varied in 

 different fields in spite of a similar intensity of attack. I think we 

 may assume that the " honey dew " produced by any given number 

 of healthy insects under similar conditions is approximately the same 

 and the variation must therefore be due to variations in the quantity 

 of the exudations from the cane. It seemed that the healthiest and 

 finest canes produced the most gum, and it may be that as the exudation 

 from the cane, is a defensive weapon, a healthy cane is better 

 equipped for the fight and consequently produces more gum. On 

 the other hand it may be due to variations in the cane induced by 

 chemical differences of the soil on which the cane is grown. This 

 requires further investigation. The relation of sap flow and irrigation 

 to gumming is another line of research that would give interesting 

 results. 



Not only does the insect impair the health of the cane but indirectly 

 through the production of gum it has very far reaching results upon 

 the available sugar content. It is found that when infected canes are 

 crushed and passed through the factory, the crystallizable sugar 

 content is much reduced. How far this is actually due to the presence 

 of the gum and how far to subtle changes induced within the cane 

 I am not in a position to state. A very simple experiment proved 

 that the " honey dew " reduced and even inhibited crystallization, 

 and in any case the reduction in sugar output is traceable to the 

 ravages of the insect. 



The gravity of the situation from a commercial standpoint is 

 obvious. All the cane passed through the factories is gummy to a 

 greater or lesser degree and not only is such cane far more difficult 

 to work, but the percentage of crystallizable sugar obtained is so 

 reduced as to entail a loss to the Sugar Company of hundreds of 

 thousands of pounds. 



SUGGESTED CONTROL MEASURES. 



The nature of sugar cane is such that it is impossible to carry out 

 any prophylactic measures whilst the cane is growing in the field. 

 It might be possible to remove the gum from the canes, assuming 

 that the gum alone is responsible for the reduced sugar output, but this 

 would be by no means easy and when one realizes that the factory at 

 Nag Hamadi deals with over a million canes daily it is difficult to see 

 how it could be carried out practically. It is much more sound to 

 deal with the cause than to pay attention to the effect of the attack, 

 and the most effective lines of control are those directed to the " sets " 

 planted and to the methods of cultivation. 



