CONTROL FOR \\UITE GRUBS. 7 



grub present ; no sign of fungus. Pot No. 10, soil water- 

 logged ; four grubs dead and rotten as though killed by 

 excessive moisture. Pot No. 12 (check), one dead from 

 biting. 

 1st October — Pot No. 4, the last grub dead ; no fungus showing. 

 Pot No. 7, two grubs have been killed by biting, but 

 there is no sign of fungus. Pot No. 11, one grub has 

 been killed by biting, but no sign of fungus. 

 At this stage the experiment was discontinued. It will be noted that 

 the disease was not very virulent, probably because the temperature in 

 each case was too high. This conclusion is borne out by the fact that 

 practically all of the grubs that succumbed to the disease were in the 

 cooler temperature of the verandah. The three deaths from fungus in the 

 checks was evidently due to a lack of care when examining the pots, for 

 it would be a simple matter to transfer the spores on one's hands. 



Artificial Propagation of the Fungus. 



Since the Muscardine fungus was again in evidence at Greenhills. and 

 I had had reports of its activities in other districts, I decided, toward the 

 •end of 1918, to try propagation of the spores art'ficially. Upon presenting 

 the matter to the Cairns Canegrowers' Association, the plan was heartily 

 endorsed and funds supplied for the construction of a large cabinet, built 

 ■on the lines of those used so successfully in Trinidad.* Ours was built of 

 liardwood, hence very strong to withstand the pressure of steam for 

 sterilizing. This metal-lined box was 6 feet high, with ten shelves made 

 of narrowly-corrugated iron 2 feet 9 inches square. (Fig. 2.) The food 

 for the growth of the spores was deposited on these shelves and subjected 

 to sterilization by steam on three successive days before inoculation with 

 spores from a pure culture, which had been previously prepared from grubs 

 that had s-uccumbed to the disease. 



The first trial, using cooked rice as a substratum, placed about half 

 an inch thick on the shelves, did not prove satisfactory for some reason. 

 At any rate, impurities got in to such an extent that the Muscardine growth 

 was practicall}^ eclipsed by other moulds. 



I experimented with various other starchy substances, since the 

 price of rice was almost prohibitive. Corn-meal had been used in this sort 

 of work in Illinois, t and I found that it did even better than rice, when 

 finely ground, for the mat of spores on this substance was perfect. 

 Furthermore, I had almost equal success with sliced sweet potatoes, 

 which were placed in the cabinet raw — the sterilising steam being 

 sufficient to cook them. 



Under laboratory conditions here, during the summer season, the 

 fungus begins to show as compact white spots one day after planting, and 

 signs of the green spores are noticeable in the centres on th(^ second day ; 

 within a week the whole substance is a compact mass of the green fruiting. 



* Board of Agric, Trinidad, Circ. No. 8. 

 t 111. Agric. Exp. Sta., Bui. No. 38. 



