December, '19] ILLINGWORTH: white GRUBS AND SUGAR CANE 453 



this is particularly true with sugar cane, for experiments have demon- 

 strated that a 30-ton crop removes from the soil 102 pounds of nitro- 

 gen, 65 pounds of potash and 45 pounds of phosphate. Land poor in 

 these elements naturally produces cane of inferior quality, which easily 

 succumbs to grub injury. Experience has shown, that for best results, 

 small experimental plots should be developed in each locality, or class 

 of soil. In Hawaii this diversified testing is done by the Planters' 

 Experiment Station, with such efl&ciency that they have found that 

 under certain conditions it pays to apply 1,200 pounds of mixed fer- 

 tihzers, containing 11 per cent of nitrogen, and on top of this, to add as 

 much as 500 pounds of sulphate of ammonia or nitrate of soda. That 

 is to say, the idea is to apply as much fertilizer as will produce a profit. 

 They also use lime freely. It is by such methods that the output of 

 these small islands has been increased from 75,000 to over 600,000 tons 

 of sugar, in the history of the Station. 



Comparatively speaking, little fertilizer is used in Queensland; many 

 of the newer farms get none at all. Consequently, I wish to emphasize 

 not only the value of manures as a factor in grub-control, but further 

 to say that under scientific application they will pay a handsome profit 

 on most soils. 



Speaking generally, grubby-soils are lacking in humus. This is 

 true of all of those that I have tested. Experiments have demon- 

 strated that the grubs prefer partly decayed organic matter to li\ang 

 roots. As a matter of fact, they live happil}^, and develop well in rich 

 soil alone, even when all roots, trash, etc., are removed. Moreover, 

 it is a well-known fact that their bodies are always full of earth during 

 the feeding period; and from this they derive their principal supply of 

 nutriment, by extracting the humus, if present.- 



Where soils are poor in humus, and all organic matter is removed by 

 the destructive methods of farming now in vogue in Queensland, the 

 grubs are compelled to feed upon the living roots or starve. Fur- 

 thermore, we know that humus has a remarkable affinitj^ for arsenic, 

 which may be made use of, as I shall point out, later. 



What is needed is a method of conserving all trash, and waste from 

 the crop, together with a regular rotation of green-crops. Sooner or 

 later all farms must come under this practice, if the productivity of the 

 land is to be maintained. In line with this advice, I wish to call atten- 

 tion to the large areas at Goondi — the Mundoo section, wliich pro- 

 duced splendid crops of cane for a few years, but now, is said to be so 

 worn out that it will not pay to work. .Vpparcntly many other cane 

 areas are fast approaching this condition, even though only a very few 

 crops have boon taken olT. 



I have onipiiasized surface cultivation mainly l)ecause of its value for 



