A STUDY OF THE FACTORS OF CONTROL. 87 



more or less distasteful to the grubs, was either too expensive or injurious 

 to the cane-roots. Mr. Tryon (19) experimented with common salt. 

 Avhich had been advocated, and found little or no benefit, except when 

 applied in such quantities as would involve a large monetary outlay and 

 be injurious to the cane-plauts. He also experimented with kainit and 

 found that the grubs survived an immersion in a fairly strong solution 

 of this potash salt ; moreover, in the soil it had no influence on the grubs. 



Mr. W. T. Paget (23) reported that he had also tried salt, kainit, 

 lime, and potash on his fields at Mackay, with only negative results. The 

 Colonial Sugar Eefining Company (36) (38) refer to the use of moth- 

 balls and a substance called vaporite, which were applied in the fields at 

 (xreenhills, but proved absolutely useless. Along this same line, ]Mr. 

 •Jarvis (72) experimented with dichlorbenzol, which was imported from 

 <Termany at considerable expense. This, when used in heavy doses, was 

 effective in destroying grubs that were compelled to remain near the 

 fumes, but the expense would prohibit its use in the field. Mr. Jarvis 

 (82) also experimented with creolin, creosote, and borax, finding them 

 ■effective against the grubs M'hen used in large doses, but the price was 

 prohibitive for field practice. His experiments also indicated that salt- 

 ])etre, barium chloride, and hellebore were ineffective when applied to 

 the soil. 



(2) Insecticides that have been more effective, and that have met 

 with practical application for years, are — Kerosene emulsion, carbon 

 bisulphide, cyanide of potassium, and arsenic in various forms. 



Mr. Tryon (19) states that it has been proved experimentally that 

 sugar-cane grubs die in ground saturated with kerosene emulsion. In 

 The United States this treatment was formerly used rather extensively 

 for destroying grulis in lawns, &c., but it has gradually been replaced by 

 •other treatments, since the expense is almost prohibitive. 



One of the oldest remedies, as well as one of the most effective under 

 i-ertain favourable conditions, is the injection of carbon bisulphide into 

 the soil, though its use, too, in recent years, has been made almost 

 ]irohibitive by increasing prices. Mr. Tryon (19) suggested its appli- 

 <-ation for the destruction of cane-grubs, quoting references to its 

 successful use in the United States. A decade or so later it was used 

 rather extensively at Mossman and ]Mulgrave (38), Avith apparently 

 good results. Eight drams of the chemical per stool was injected into 

 the soil 2 inches deep, one or two injections being given to the stool 

 recording to whether it was small or large, the requirement per acre 

 l^eing about six gallons, one man doing about one acre a day. It was 

 suggested that best results were secured when the ground was dry, for 

 otherwise the remedy would not act. It was also found that it was 

 l)est to make the injections above the grubs, the heavy vapour 

 ])ermeating the soil downward. As the carbon bisulphide, in large lots, 

 costs 20s. per five-gallon drum at Southern ports, the cost per acre was 

 approximately 34s. Smaller doses were applied at IMulgrave, viz., 3-J 

 drams to the older and 2 drams to the smaller stools, at least two 

 treatments being given; 60 acres alluvial river-fiats were treated at a 

 cost of about 30s. per acre. One farmer of the district also applied a 

 mixture of two parts carbon bisulphide and one part kerosene on old 

 cane attacked by about twenty grubs per stool, with the result that the 

 treated cane recovered, whilst that surrounding it was practically killed. 

 Investigations were said to have shown that 80 per cent, of the grubs 



