THE AGWCLLTLUAL XKWS, 



•liNK 29, 191S. 



PLANT DISEASES. 



EEL-WORM DISEASE (BLACKHEAD) OF 



BANANAS. 



A striou- ;trttLtiou "f ibc coarse banana kncwN in 

 ■Grenada as the bliiggoe. i.- reported from thiit island by the 

 5?upenntendent of Agriculture. It is describe*! by Mr. Moore 

 *? follows: — 



'It apijears that the di.^ease may develop iu plants ol all 

 agti. though its presence i~ most evident to the casual 

 observer in plants that are approaching or have actually 

 jeached a fruiting .-.tage. 



'A common characteristic is the drying of the outer leaves 

 and then of the partly developed bunch, the fruits of which 

 often dry to a hard blackened condition when only "J or 

 ii inches long. 



'Plants examined do not show signs of disease in the 

 parts most distant from the bulb ami roots, the general 

 impression conveyed by a survey of the afiected plants being 

 that they are suffering from lack of water and nourishment. 



'In every instance, examination of the bulb and roots 

 revealed a root sy.^tem almost entirely dead, or partly dead 

 and dying The dead roots were either entirely black, or 

 black between the cortex and the central column. The outer 

 part of the bulb from which the roots arose presented the 

 same black disorganized appearance, and this was repeated to 

 a lesser degree on the bulbs and roots of young suckers 

 arising from the diseased parent.' 



Several hundred clumps have already been seen with the 

 eymptoms of this disease. The following notes refer to the 

 conditions under which it occur> in three distinct localities. 



A. About 300-100 stools of bluggoes planted with 

 material from various sources two years ago; a crop of cane 

 recently reaped from the land: young cacao plants set to each 

 ttool. Two types of .soil, one black and heavy, one brown 

 and loose; disease occurs on both. Trouble observed ever 

 since plants reached maturity 



B. A field <if several acres of limes interplanted last 

 year with bluggoes, now fruiting for the first time. A view 

 of the whole field conveys the impression that all the outer 

 leaves of the bluggoe plants havt; been scorched. The dying 

 commences along the margins ol the leaf blades. 



C Isolated clumps anumg mature cacao affected. The 

 external symptoms, and the condition of the roots and bulbs 

 are the same in all three cases. 



Spirit-preserved material from the first two localities 

 wa.1 forwarded by Mr. M(pore for examination. Slices of the 

 diseased bulb .show peripheral blackening penetrating to a 

 depth of about an inch in places, and blackened areas isolated 

 in section but connecting with the exterior at a higher or 

 lower point. The thick roots have .short vertical cracks, 

 connecting with extensive discoloured patches spreading 

 upwards and downwards in the tissue of the cortex, reaching 

 in many cases to the central vascular cylinder but not pene- 

 trating it. The di.scolourcd tissue is in various stages of 

 disorganization, but in much of it the cell wallN wore not 

 visibly decayed. 



The affection his the geni lal a|i|)eaian(e of a fungoid 

 disease, bul neither hypliae nor bacteria were pre.sent to an 

 extent or with a unitormity suggesting more than a saprophy- 

 tic role. On the other hand, niMiiatodes (eelwrrms) were 

 regularly .present in all the material examined; their eggs 

 •were present in the lea.-,t altered and deepest seated of the 

 discoloured tissue, and in some cases the worms themselves 



were seen occupying the cells of undecayed tissue close to the 

 central cylinder of the roots. 



Reference to literature shows that .V. A. Cobb (/nunia/ 

 cf A^riciiltiiial Rc^ianli, Washington, Vol. IV, pp. ."i61-8) has 

 described an eel-worm, Tyh iic/ius n'liii/is, as the cause of 

 a serious outbreak of a disease of bananas in I'iji in 1S90 91 

 and has found the same species attacking sugar-cane in. 

 Hawaii. S. F. Ashby {Hiilktiii ,tf Ihc D,/>aiiiin'iif ,>/ Agriiii/- 

 ini\, Jamaica, Vol. II, p. 316) describes a type of so-called 

 blackhead disea.se in .lamaica. which be attributes to an 

 eel-worm (identified later by Dr. Cobb as Tylcihhus simi/is). 

 The description of the condition of the roots and bulbs agrees 

 in general with that given above. 



From the nature of the infestation -minute worms living- 

 and laying eggs deeply within the tissues, capible of living 

 in the surrounding soil, probably, as is the case with related 

 species, resisting drying for raontiis or years, infesting suckers 

 on diseased plants from their earliest inception, possibly 

 living on other species of plants— it will be seen that control 

 may present difficult problems. 



The first essential must bi complete avoidance of the 

 use of suckers from affected clumps as pknting material 

 Where land is badly infested some other crop should be 

 substituted. Direct treatment appears quite impossible. 

 Ashby (loc cit.) remarks regarding the Jamaica disease: 

 'The worms are widely present in cultivated soils, and even 

 the roots of vigorous plants may show slight signs ol attack. 

 Unfavourable weather and soil conditions by checking active 

 root growth and forcing the plant to depend on the older 

 roots bring eel- worm injury into prominence, and make later 

 recovery more uncertain.' Observations will no doubt be 

 made as to whether more intensive cultivation will enable 

 plants to "grow away' from the disease in (Jrenada. 



Further information is being sought as to the disease, 

 and specimens of the nematode found have been submitted to 

 Dr. Cobb for the favour of identification. 



W. N. 



DEMAND FOR LIGHT WOOD. 



The Imperial Commissioner of Agriculture for the West 

 Indies has been informed that there is at present a demand 

 arising out of the conditions of ocean transport, for verv 

 light woods, suited to the purpose nf ntaking rafts and 

 eijuipment that will readily Hoat. 



There are growing in these West Indies several trees, 

 the wood of which is of very low specific gravity. Among 

 these is Oi/imma /ax'>/<i's, known in .some of these islands 

 as cork wood, on account of the lightness of its wood; in 

 others as down tree, because of the silky fibres which envelop 

 its .seed; and in other islands, as bois Hot. According to 

 XJook and Collins in their book Ecoiitimic P/aii/s nf Por/c 

 Rico, the wood of this tree is very porous, and is the lightest 

 of all woods, lighter even than true cork, the specific gravity 

 of which is 0"240, while the specific gravity of this wood is 

 only 0'120. The tree is fairly abundant in the damper 

 islands of the West Indies, and acccinling to Mr. I'lugene 

 Campbell, in a note contributed to the .li;ritn//iirit/ .\v,7'.v 

 for August 10, 1907, the down-tree is found growing plenti- 

 fully along the l)anks of all the princiiiid rivers in Mritish 

 Honduras. The trunks are used there for making raft.s for 

 floating logwood down the rivers. Some o( the trees attain 

 large (iinienslons, being 30 or !•• feet high and over "J feet 

 in diameter. In the West Indian islands, from Trinidad to 

 Porto liico, wherever the tree grows, the wood is used instead 

 of cork by fishermen lo make floats for their nets. Tl«e 



