90 AUSTRALIAN 8UGAE-CANE BEETLES AXD THEIR ALLIES. 



before they reached the third or very destructive stage ; hence these 

 plants showed no injurv, though the checks alongside were somewhat 

 fallen. 



11th March the cane in the plot with 200 lb. arsenic was standing 

 erect, in marked contrast to the check-plots on either side in which all 

 the stalks had fallen flat on the grouncl. It was so encouraging that I 

 decided to have a photograph made of it (Plate XII). The plot with 

 100 lb. arsenic was not quite as perfect, some of the stools being somewhat 

 fallen ; and the injury was proportionately more where less poison had 

 been used. The 80-lb. plot was fair, the 60-lb. plot showed little benefit. 

 and the 40-lb. plot none. It was very evident that we must increase 

 the dose to 200 lb. for control. The plant cane in all the Badila plots 

 of the other field was still green. 



Following upon these observations there was a solid month of 

 deluge. Water stood in the field in lakes, and in some places the cane 

 was washed away. To make matters worse, there was considerable wind, 

 so most of the heavy cane was lodged. In our Badila plots, where 

 we had applied arsenic in the drill before planting, the cane was all 

 severely injured by the grubs, so that there was no noticeable difference 

 in the treated and untreated plots. Digging in the saturated soil, 13th 

 April, I found all the grubs near the top ; hence the excessive moisture 

 had compelled them to leave the lower stratum where the poison had 

 been placed, and they had continued their destructive work, eating right 

 into the stalks near the surface of the ground, in some eases. ^Moreover 

 the encouraging results that I have noted in the D 1135 field were also 

 somewhat obscured by the effects of the wind and water. The erect 

 cane in the poisoned plots had lodged, but it still held its head several 

 feet above that in the checks, for its roots were solidly in the soil and 

 practically uninjured by grubs. 



This evidence was encouraging, but it is still inconclusive ; I had 

 hoped to be able to clear the matter up with all the various experiments 

 that we had in hand ; but the indication is now that for best results the 

 poison should be placed nearer the surface, especially for w-et seasons. 



At first thought it would appear to be an easy matter to poison the 

 adult beetles, especially the greybacks. Avliich are such voracious feeders. 

 Indeed Mr. Tryon (19) recommended the use of arsenicals for this 

 purpose ; but states that field applications were disappointing. After 

 experiments with beetles in confinement he concluded that they are 

 either very tolerant of poisons, or if they succumb to them it is only 

 after a considerable interval has elapsed, since, he says, they die no 

 sooner than do other beetles that in confinement subsist on unpoisoned 

 food. Mr. Jarvis (70), also, experimented on beetles in the laboratory, 

 but his results, too, were very inconclusive : beetles eating the poisoned 

 foliage lived for 9-10 days while those without poison died in about 

 14 days. Furthermore, experience in the United States with beetles 

 of the genus Lachnosterna showed that they were almost immune to 

 the ordinary poisons. Still I would urge further experimentation along 

 this line with the use of proper controls. 



(3) Collecting beetles is a time-honoured practice; for many years 

 it has been the principal method of combating similar pests in Europe. 

 It must be recognised, however, that there they have a tremendous 

 population, and labour l^eing cheap they have been able to collect 

 practically all of the pest at a minimum outlay. In this new country, 

 where the uncultivated natural breeding-ground of these pests is so 



