MONTHLY NOTES ON GRUBS AND OTHER CANE PESTS. 2T 



free from attack for about two years. Oue fortunate thing, however — 

 a large percentage of the grubs are attacked by the Muscardine fungous- 

 disease — fully 30 per cent, in one field examined. 



In the region about Cucania and Harvey's Creek a closely-related 

 grub, Lepidiota caudata, is in evidence, especially in the grass land. In. 

 one pit, a cubic yard in size, I unearthed five different species of grubs 

 — the common grey-back, L. caudata, L. f rendu, and tw^o smaller species — 

 all cane pests; thus clearly showing that these pests inhabit the wild 

 land, and are ready to destroy sugar-cane if planted there. 



It must be remembered that most of the land along the liiie after 

 we pass Gordonvale was originally scrub, so these beetles, which are 

 natives of the forest country, have evidently followed the advance of 

 cane up the valley. As a factor leading to this conclusion, I may men- 

 tion the farm of Pollard's at Babinda, which Avas cleared out of the 

 scrub thirty-five years ago, and was free from grubs until two years 

 ago. The grey-backs have devastated two of his fields this season. 



The cane planted on newly-cleared scrub land at Babinda is 

 apparently free from grubs, though this immunity is not apt to last long 

 unless steps are taken to combat them. 



The Mobsman District. 

 I was interested to learn that though the grubs were once a serious- 

 pest in this section they are now little in evidence. The growers attribute 

 this to the fact that they use sulphate of ammonia extensively as a fer- 

 tiliser. There is probably some foundation for the supposition ; in fact, I 

 collected some evidence along this line last year. Part of an infested 

 field at Gordonvale had been treated with sulphate of ammonia, with 

 a result that was remarkable at cutting time — the treated cane stood 

 erect and vigorous, while the untreated was all uprooted, lying about on 

 the ground. (See Monthly Report for August, 1917.) 



We have not been able to demonstrate yet whether the sulphate of 

 ammonia has any direct acti.on upon the insects, but we know that its 

 action so stimulates the plant that it rapidly sends out new roots, and if 

 these are produced faster than the grubs destroy them naturally the 

 cane is able to hold its footing. Whatever its relation to the grubs, we 

 would strongly advocate the use of a nitrogenous fertiliser upon most 

 of our soils. Since nitrate of soda is a foreign product and very difficult 

 to procure, we can get best results at present from the use of sulphate 

 of ammonia. This latter substance really has a higher efficiency of 

 nitrogen, though best results are obtained upon soils which are limed. 



Serious inquiry at ]\Iossman developed no other factor which could 

 account for the disappearance of the grubs. It is interesting to note that, 

 on the two farms where I found the ravages of the grubs, filter-press 

 had been applied in those particular fields, thus leading to what is per- 



