452 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



perfect cane goes down to destruction within a few weeks, during 

 March. Once the roots are eaten off, the slightest wind pushes the 

 stools over in that loose soil; then deterioration quickly sets in. 



In 1911, a conservative estimate^ of the annual loss in the Cairns 

 district, through grubs, was 25 to 30 thousand tons; and this loss con- 

 tinued year after year in spite of all efforts to combat the pest. In 

 one year the Cairns growers collected 22 tons of beetles and 9 tons of 

 grubs, at an expense of over £3000; with no apparent diminution in the 

 pest. On this point the following interesting figures^ will help one to 

 understand what a ton of beetles represent: One pound of beetles 

 equals 250; in one ton there are 560,000 beetles, 60 per cent females 

 equals 336,000 each laying eggs which produce 25 fully grown grubs 

 equals 8,400,000. Since it is estimated that 16,000 grubs are sufficient 

 to destroy one acre of cane; one ton of beetles, therefore, could destroy 

 about 500 acres of cane. 



From data at hand, it is easy to see that in all the cane-growing 

 districts of Queensland, the losses from the grub pest alone undoubtedly 

 run into hundreds of thousands of pounds. 



Combating the Pest 



I must admit that the problem seemed hopeless at first; but I am 

 beginning to see light. In fact, I am more and more encouraged as the 

 investigation proceeds. 



Control measures have been developed along several lines, the most 

 important of which are: (1) stimulating vigour in the plant, (2) 

 egg-destruction by cultivation, (3) apphcation of poison, and, (4) 

 removal of feeding-trees. 



There are numerous factors which bring about increased vigour, and 

 all of them should be considered as valuable aids in combating the pest, 

 for if the cane is in a thrifty growing condition it will resist the grubs to 

 a considerable degree. Among these factors, I would suggest, the 

 apphcation of Hme and fertihzers, supplying humus, and thorough 

 cultivation. 



Lime, as every grower knows, improves the physical condition of 

 clay soils, and assists in the rapid change of plant-refuse into humus. 

 It improves the health of soil bacteria and fungi, in other words, which 

 are all-important in the growing of crops. It is well recognized, too, 

 that a leguminous green-crop does very poorly on land without lime, 

 which is essential to the bacteria forming the nitrifying nodules on the 

 roots. 



The use of fertilizers is important to the growing of any crop, but 



1 Aust. Sugar Journal, Vol. 3, p. 199. 

 ^ Aust. Sugar Journal, Vol. 2, p. 443. 



