872 Agncultural Gazette of N.S.W. [Dec 2, 1920. 



during the night, congregating underiieatli the trap, and should be regularly 

 collected and destroyed each morning. The soil just beneath the trap 

 should also be examined. It is inadvisable, unless under strict supervision, 

 to place the traps among apparently clean stools, as otherwise the beetle 

 may be attracted to healthy plants. 



Where there is danger of a clean plantation becoming infested from an 

 adjoining infested one (a condition previously stated to have actually 

 occurred), traps can be usefully employed as a first line of defence. A 

 double row of traps (the traps in one row arranged opposite the spaces 

 between the traps in the other) can be placed between the two plantations, 

 but nearer the infested one, and examined each morning, and any beetles 

 destroyed. It must be borne in mind, however, that with such a procedure, 

 rigid supervision of the traps is essential so that all beetles can be promptly 

 collected and destroyed. 



Natural Enemies. 



Xo natural enemies of the insect were found on the Tweed River, and 

 the fact that the original home of the beetle is unlvnown makes the dis- 

 covery of its true parasites rather difficult. Muir found no direct parasites 

 either in Borneo or Java, but he state.s that they were attended by Hydro- 

 philids and Histerids. The Histerid beetle, Plwsius javanus, was intro- 

 duced from Java into Hawaii as a parasite of an allied species, tlie cane 

 beetle borer (Rhahdocnernis ohscvra). It failed to establish itself, how- 

 ever. Jepson, in his mission to Java in quest of the natural enemies of the 

 beetle, found the same beetle to be the most effective parasite of the banana 

 beetle. He accordingly in 1913 introduced it into Fiji, where the banana 

 beetle was doing considerable dama.ge. Four yeai*s later, however, its 

 establishment in Fiji also appears to be doubtful. Writing in 1917, Knowles 

 states : — " Nothing has been seen or heard during the year of the predatory 

 beetle Plcvsius javarms, introduced from Java in 1913, but there is no 

 reason to suggest any modification of the opinion expressed by Mr. Jepson 

 last year that this does not necessarily mean that the beetle has died out, 

 as it is not a very prolific one, and development is extremely slow." Xo 

 conclusion can, however, be drawn, and from the nature of the .Tweed 

 River infestation I am of the opinion that, if this predatory beetle can be 

 established, it would be of some value in controlling the banana beetle. As 

 this Histerid is predaceous in both larval and adult stages, it is unlikely 

 that it would be injurious in any way if introduced. Further information 

 as to its habits and value as a check on the banana beetle is being con- 

 sidered before deciding upon its introduction. 



Samples of potash salts obtained from the water hyacinth (Eichhornia 

 crassipes) that abounds on the northern rivers have lately been submitted 

 to the Department for analysis. It was found that the material contains 

 7*7 per cent of moisture and 36*12 per cent of potash (K2O), the latter 

 being present as chloride and sulphate. At the current unit value for 

 potash, this fertiliser is worth about £20 15s. per ton. — F. B. Guthrie. 



