222 



THE aGRICULTUKAL NEWS. 



July li', 1919. 



PLANT DISEASES. 



INVESTIGATION OF THE FROGHOPPER 

 PEST AND DISEASE OF 

 SUGaR-OANE* 



{CondiuM.) 

 M.\NUUISG. 



' The subject of manuring, while I regard it, together 



with that of cultivation, as of most importance, is at the 



Same time the one un which, owing to the variety and 



■(Complication of the local factors concerned, it is most difficult 

 to oiler mora than general counsel. 



' Pen manure. 'One may' state with assurance that 

 much more pen manure should be used : the average 

 manager will heartily agree, but enquire where it is to come 

 from. The question should have the close attention of 

 owners and their representatives, so that liVieral expenditure 

 on the construction and modernization of pens may not 

 only be allowed, but an active policy in this direction 

 demanded. Everything should be done for the conversion 

 of the largest possible amount of material into pen manure, 

 and for its pre.servation in good condition. The best 

 means to adopt might , with advantage, be mads the subject 

 of a special enquiry. Much improvement on present 

 practice is ceriainly possible. 



• It would be one of the advantages of rotation of crops 

 that more stock food could be grown on the estate, and 

 this, combined with an increase in implemental cultivation, 

 would enable more animals to be usefully and economically 

 kept. 



' Connected with the subject of pen mauure there is the 

 difficulty in regard to many fields of its transport over 

 traces made impassable to carts for much of the year by 

 mud. This is given, and with obvious justification, as the 

 reason for the remoter areas on some estates being starved. 

 The difficulty is f-w which from its magnitude can only slowly 

 be removed, and it seems a pity that in the long history of 

 the estates in question, no policy has been adopted of 

 gradually building up the traces. Their condition involves 

 a tremendous annual waste of energy, and is an effective 

 check to the practice of good agriculture. The army 

 transport services of several great nations have been 

 contending for years with similar difficulties in Flanders, 

 and Pome of the methods worked out might find an 

 application in Trinidad. There are sections in the Naparimas 

 where the control of root disease requires the services of 

 an engineer rather than of a mycologist, and where a steam 

 roller working on the traees would have more effect on 

 the crop than a steajn plough in the fields. 



Green dressings. 'The matter of green dressings is 

 not w> simple as it looks, nor so well understood as it 

 might be. There i.s a good deal that is doubtful as to 

 what happens to the material under various conditions of 

 8oil and moisture, and as to the nature and extent of the 

 benefit derived. Recent work in India is throwing sonic 

 light on these problems. 



'The purpose of the green dressing is threefold: to 

 supply organic matter for the production of humus, to 

 open 'ip the soil for the access of air, and, in the ca.se of 

 lf(i"minou8 crops, to derive a supply of nitrogen from the 

 rtiiii<..'-|,bere. The fir.st two parposcs are served by any 

 Icind of plant material, and where sufficient for the ptirjiose, 

 can be produced in connexion with a saleable crop, as is 



* llc|iorl 

 Trinidafl. 



by Mr, \V, NowbU on lii» invostigatir.ns in 



the case with the sweet potato in Barbados, the choice of 

 a legume may be overruled by this consideration, nitrogen 

 being supplied in some other form. If the full manurial 

 ellVct is needed, a leguminous crop should be grown and 

 turned under complete, or b-ttcr, its produce in the form of 

 peas or beans used as stock food and returned to the soil 

 in this way. If the produce is sold, the manurial 

 increment is by so much diminished. 



' Where a green dressing is thickly sown and forms a 

 dense cover, the protection of the soil is no small part of its 

 value. The need for aeration in the silt soils of the colony 

 has already been referred to, and it would appear that in 

 the choice of a green dressing for jthese lands, its effective- 

 ness in regard to this function should be a first consideration. 

 The use of a woody, deep-rooted plant is indicated. I would 

 suggest careful trial of pigeon pea, if it is practicable 

 to get the stems turned deeply into the soil. The decay of 

 such material leaves channels for the access of air, and the 

 results of measures taken to this end in India havo been 

 surprisingly good. 



Muleh. 'Sugar-cane supplies its own mulch in the form 

 of trash. I got the impression, which may or may not be 

 justified, that in this direction as in others, not so much care 

 is taken as in the Northern Islands to make the most of the 

 benefits available from this material. Like the conservation 

 of pen manure, the best disposition of trash is a matter 

 well worthy of being made the subject of a careful enquiry. 



THE CHOICE OY ROI.\TIOS CROPS. 



'What is most to be desired for Trinidad agriculture is 

 a rotation crop with a value sufficient to secure, without a. 

 sense of sacrifice, its alternation with cane as a general 

 practice. No such crop is at present visible. 



'Among tne cr ps which are available, two lines of 

 development are suggested by the imports of agricultural 

 produce, i.e. the production of stocK food and of dholl, in 

 both of which there is a trade of very considerable annual 

 value. 



'Of root crops used as food, there are sweet potatoes, 

 yams, eddoes, tannias, cassava and artichokes, all desirable 

 from the point of view of this report, as involving considerable 

 cultivation The prospects for the development of an 

 industry in the production of farine might be considered. 



'Cowpeas and horse beans are already in use, but their 

 position and 1 hat of corn is rather that of catch crops. 



'Sea Island cotton is nnsuited to the soil and climate ; 

 the perennial cottons, if planted in mass, would be likely to 

 suffer too much from stainer borne disease 



'The position ot castor ia worth watching. 



lllONEKAL. 



'I wi'»h to take this opportunity of saying, in justice 

 to Mr. Williams, Rntomologistin-Charge of Froghopper 

 Investigations, that the main conclusions here set out are 

 those which he himself had reached, or was reaching, though 

 of course F cannot commit him to my expression of them. 

 It is desirable to .say this, since his report will appear at a. 

 later date than mine. If 1 have been able in the short time 

 at my disposal to ai)proach a correct diagnosis, such a result ' 

 was rendered possible only by .Mr. Williams's services in the 

 sclecti'in of the most important points of vantage, and by 

 the opportunity of reference to the data concerning blight ■ 

 which he hns accumi'laterl. ■'■> 



'I have to express my [)ersonal thanks for the unfailing'; 

 consideration a';d helpfulness with which I was received by- 

 all who were concerned with' my visit. I am espedially 

 indebted to the officers of the Department of Agriculture 

 and of the Hoard. 



