88 AUSTRALIAN SUGAR-CANE BEETLES AND THEIR ALLIES. 



\v-ere killed by the treatment. The remedy in some instances was applied 

 too late, after the grabs had eaten off most of the roots of the yonng' 

 cane ; hence it proved ineffective. 



IMr. Tryou (45) brought to the attention of the growers experiments 

 that had been carried on in France, using a solution of cyanide of 

 potassium for the destruction of soil-frequenting insects, with a view to 

 its application for scaraba-id gru])s. Apparently, however, no immediate 

 use was made of this information. Mv. Jarvis (82) made some 

 preliminary laboratory experiments, using the above information, and 

 got rather effective results in killing grubs in the soil, but the investi- 

 gation was not continued, due to the high price of the chemical, which 

 was almost unprocurable. 



During the recent campaign against the green Japanese beetle, in 

 New Jersey, Mr. J. J. Davis (107) used sodium cyanicle in solution on 

 a very extensive scale; this was applied to grass land, while the grubs 

 were near the surface. Tank wagons with a capacity of 600 gallons, 

 drawn by tractors, were used in this work. He found that it required 

 160 lb. of the salt with 12,000 gallons of water per acre to kill 95 to 

 100 per cent, of the grubs. 



Arsenic, though an old and standard remedy as an insecticide, was 

 apparently first used successfully in combating cane-grubs by Mr. C. E. 

 La Caze (56) on the Herbert River. He reported to me that he was 

 eaten out year after year, losing many thousands of tons on his three 

 farms. Being faced with bankruptcy he decided upon extreme measures.. 

 AVhen he learned that white arsenic would destroy termites (white 

 ants) he at once decided to try it for the destruction of the grubs. 

 He hit upon a plan of mixing the poison with meatworks manure, and 

 arranged to have the mixing done at the meatworks. Since arsenic 

 was cheap, he used 14 lb. for each cwt. of the manure, and applied 

 5 cwt. of this fertiliser per acre, placing it in the drill before planting. 

 He said the results were immediately noticeable, and that there had 

 been no further grubs on that land since. 



These results were most interesting, but since I was told that many 

 of the beetle feeding-trees were removed about that time, this may have 

 also had an important bearing upon the disappearance of the grubs. 

 At any rate the results were not conclusive, and the experiment should 

 be repeated with proper check-plots. 



Mr. Girault (57) also, recognising that the grubs swallow a great 

 deal of earth, experimented with poisons in the soil, and though his 

 work was on a laboratory scale he found that this treatment was effective 

 against the pest. 



Continuing this line of investigation, ]\Ir. Jarvis (88) finally 

 modified the application by coml)ining the pi)isons with green foliage of 

 cowpea, which he ])uried in the i)ots with grubs. He experimented with 

 Paris green, London purple, and Avhite arsenic, using these poisons at 

 the rate of 8 oz. to 1 cubic foot of soil, from which he got effective 

 results. In devising a means of applying this remedy in the field, ^Ir. 

 Jarvis advised ploughing a trench close alongside the stools, and sowing 

 cowpeas in the bottom, leaving the furrow open while they grew. In 

 ])ractice this would hardly be wise procedure, for it would be apt to 

 dry the ground out too much. Mr. Jarvis (98), however, had a small 

 plot treated in this way on a farm near Gordonvale. The cane had been 

 planted in August; the drills made alongside and sown with cowpeas. 



