Plant Sanitation. 



258 



[March, 1909. 



chambers, when the ' 1 pyenidia " hither- 

 to unseen under the barb, develop and 

 discharge the spores in spiral or contort- 

 ed, gummy threads, which, though white 

 when first exuded, rapidly become dark 

 brown or nearly black as they assume 

 the mature two-celled form. In the roots 

 of trees lately examined, there was 

 strong evidence that young trees had 

 become infected through cutlass wounds 

 made in the stems just at the surface of 

 the ground by workmen when "brushing" 

 or " billing" down the tall weeds which 

 flourish in young plantations. Certain 

 mites were noted during our studies 

 which carried some of the spores attached 

 to the hairs of their bodies, showing 

 the possibility of transferring spores 

 from one point to another by insect 

 movements. 



It may be noted that in recent writings 

 reference is made to a fungus determined 

 as Lasiodiplodia sp., but that all 

 writers have, to the present time, been 

 careful to place it among the so-called 

 fungi imperfecti, which means, that its 

 history is imperfectly known. Our exa- 

 mination of the original specimens, how- 

 ever, showed nothing more than the 

 organs of Diplodia cacaoicola P. Henn, 

 and hence it would appear that this fun- 

 gus is accountable for "Pod disease" — 

 " Brown Rot," for "Stem disease" — Die 

 Back," and also for the "Root Disease " 

 of young plantations. The same f uugus, 

 or possibly one nearly allied, has been 

 detected by us on Castilloa elastica, 

 causing a disease of the roots, on sweet 

 Orange stem affected with "Root Rot" 

 and on the fruit of CLusia rosea in the 

 open forest ; which latter appears to be 

 strong evidence that the fungus is indi- 

 genous to the colony and widely distri- 

 buted, although only brought to notice 

 during recent years. It will be further 

 noticed that in lectures recently deli- 

 vered no mention is made of any disease 

 caused by Diplodia cacaoicola, and that 

 the greatest amount of disease is attri- 

 buted (even canker) to the action of 

 Lasiodiplodia sp., for the determination 

 of which American botanists appear to 

 be responsible, but which may probably 

 prove to be a form of, if not actually 

 identical with, our long known Diplodia 

 cacaoicola. It will be remembered that 

 the identical sample on which the deter- 

 mination was made, was collected by 

 the writer, who found nothing more in 

 it than could be most properly ascribed 

 to Diplodia. It is possible, of course, 

 that some points found by others have 

 been overlooked by him, but in any case 

 it is desirable that such points should 

 be fully worked out, so as to confirm 

 the determination, or to rid us of what 

 may prove to be only the bogey of a 

 disease. 



With regard to measures to be taken to 

 control or prevent the spread of diseases 

 caused by Diplodia, I am in full accord 

 with Stockdale, who writes: "This 

 disease does not readily attack trees in a 

 vigorous condition of health. Every 

 effort should therefore be given to 

 thorough cultivation, all diseased bran- 

 ches should be cut out and burned, and 

 all wounds, should be followed by an 

 application of coal tar or some similar 

 (antiseptic, J. H. H.) substance. " The 

 rapid growth made by the spores, which 

 it has been seen are capable of infecting 

 a tree in a single hour, clearly shows how 

 important is such advice as that given 

 above, and not alone by Stockdale, but 

 by all writers, among whom there is 

 an agreement of opinion which neces- 

 sarily adds to its importance. When it 

 is seen and realised by the planters 

 how dangerous must be the practice of 

 leaving naked cuts or open wounds with- 

 out a covering of antiseptic dressing, 

 how dangerous to leave quantities of 

 dead branches of prunings in the field 

 capable of propagating the fungus by 

 millions of spores, each capable of re- 

 producing the disease in an hour, and 

 how still more dangerous it is to leave 

 heaps of empty pods infected with fun- 

 gus to act as nurseries for the spread 

 of the destructive organisms of such 

 a fungus, they will readily forgive the 

 earnestness which has induced students 

 of such facts to lay them before the 

 public. When the enemy is known and 

 also the principles which retard, delay 

 or negative his power for mischief, a 

 much better fight can be maintained 

 than would be possible were we in 

 ignorance of the cause. 



So far as we are yet aware, no appli- 

 cation can be applied which would con- 

 stitute a radical cure ; but, nevertheless, 

 planters may, by keeping a course of 

 high cultivation and by adopting 

 " hygienic" and " preventive " measures, 

 do much to prevent such diseases spread- 

 ing and to secure a certain amount of 

 immunity for their estates, and they 

 certainly have it in their power to pre- 

 vent such disease attaining to epidemic 

 proportions. Further studies of con- 

 trolling influences should be made, many 

 of which are probably at work though 

 still unrecognised — such as the destruc- 

 tion of spores by insects— the "mite" 

 and the "cockroach" and certain fungi 

 parasitic on the pest ; but there are 

 many other natural enemies to the 

 growth of this fungus still awaiting dis- 

 covery. It is certain that under given 

 conditions fermentation is very destruc- 

 tive to fungus spores; and points to the 

 most suitable method of getting rid of 

 the empty pods as disease producers, by 

 utilising them for manurial purposes 



