94 



THE AGRICULTURAL NEWS. 



Maech 14, 1914. 



FUNGUS NOTES. 



REPORT ON A VISIT TO ST. LQCIA. 



The following notes are taken from a report submitted to 

 the Imperial Commissioner of Agriculture by the Mycologist 

 on the staff of this Department (Mr. W. Nowell) respecting 

 the observations made by him during his recent visit to 

 St. Lucia. 



FUXGUS DISEASES OF INSECTS. During the inspection 

 of Union estate, and on all occasions where the opportunity 

 occurred of examining citrus and other plants susceptible 

 to scale insects, the efficiency of ths control exercised upon 

 the latter by their fungus parasites was very striking. Only 

 in .the case of certain young trees not well established was 

 there any indication of need for spraying with insecticides. 

 The white-headed fungus (Ophionectria) was most notice- 

 able, closely rivalled by the red-headed fungus (Sphaero- 

 stilbe). The black fungus (Myriangium) was fairly abundant, 

 and the buff or shield-scale fungus (Cephalosporium) was 

 present where its hosts occurred. Specimens of Aschersoida 

 turUnata parasitizing a scale in.sect (Coccus mangiferae) on 

 Java plum (Eugenia jamholana) were noted in the Botanic 

 Station. There also attention was called by the Agricul- 

 tural Superintendent to a shrub infested with the Fulgorid 

 bug, Ofme)us sp., many of which were dead and adhering 

 to the twigs; these were found to be parasitized by a species 

 of Isaria. 



The fungus Septobasidium [Thelephora] pedicellafa came 

 frequently under observation on lime trees, on the twigs of 

 which it forms a bluish grey, waxy coating. When this 

 fungus was first submitted for examination it was stated to 

 be frequently associated with the death of the parts 

 affected (Agricultural News, Vol. IX, p. 286). Later, in 

 consequence of the announcement by Mr. T. fetch. Mycol- 

 ogist to the Government of Ceylon, that fungi of this genus 

 were parasitic on scale insects, the acceptance of this opinion 

 was revised, a suggestion being made that the death of the 

 parts was due to the scale insects and that the fungus is 

 probably beneficial (Agricultural Keu's, Vol XII, p. 14). 

 A careful examination was made during the present visit 

 of a well infested lime, aid specimens were collected for 

 further study. The fungus ic these examples had enveloped 

 colonies of the purple scale insect (Lepiclosap/tes beckii), and 

 in the case of the older members, the mycelium had grown 

 in under the edge of the actual scale and attacked the body of 

 the insect; but whether this had occurred before or after death 

 was not determined. The young twigs of the tree above 

 referred to were gumming freely from raised swellings where 

 they were covered by the fungus, and in some cases the part 

 of the twig lying beyond the investment was dead. The 

 number of scale insects present was far below what would 

 generally be considered capable of killing the twigs. The 

 damage appears to be due to the fungus, and since no 

 evidence of penetration could be found the conclusion was 

 reached that it is probably brought about by suffocation. 



IMMOETEL CANKER. This disease is steadily destroying 

 on all the estates visited a form of Erythrina commonly 

 grown as a shade tree for cacao and locally thought to be 

 JJ. Indica, and seems likely to cause its practical extinc- 

 tion. No fungus fructifications were found associated 

 with it, and from its general appearance it is suspected 

 to be a bacterial disease. In view of the constant wounding 

 to which the tree is subjected through being made to serve as 

 a stand for cutlasses and by the necessary lopping, often 



involving the cutting of steps in the trunk, there seems little 

 hope of any practical remedy. The substitution of other 

 shade trees is being carried out by planters, and so far, 

 Erythrina rduhna appears to be immune. In addition to 

 damage caused to the cacao by loss of protection, the epidemic 

 i> unfortunate in that it cumbers the ground with large 

 quantities of dead wood, making proper sanitation very 

 difficult. Three apparently distinct species of Ftosellinia were 

 found on this material during the visit. 



EOSELLIMA BOOT DISE.'VSE OF t.\CA0. In view of its 



importance, careful attention was paid to this disease. The 

 conclusions arrived at coincide in all respects with those of 

 Messrs. South and Brooks as published in Circular JS'o. ? of 

 this Department. Perithecial fructifications of Rosellinia 

 were again found on the mycelium enveloping a cacao stump 

 killed by the disease, though unfortunately they were not in 

 a condition to permit of the determination of the actual 

 species concerned. Fresh perithecia for this purpose are 

 much to be desired. The presence of the characteristic 

 mycelium on living and dead roots, its clear connexion with 

 conidial fructifications of the Dematophora type, and the 

 subsequent occurrence of perithecia of Rosellinia situated 

 on the same mycelium — viewed in the light of the association 

 of these three characteristics in destructive root diseases in 

 many different parts of the world — aftbrd evidence which is 

 as strong as it can possibly be without the proof of direct 

 infection from pure cultures that Rosellinia is responsible 

 for the disease. 



The actual conditions of infection have still to be 

 learned. Attempts to infect plants in tubs and pots by 

 means of material from diseased trees have so far failed, yet 

 in a gap caused by the disease in a pois-doux windbreak 

 living fence posts of white cedar (Teconvi leuco.rylon) and 

 other wood were found to be strongly attacked, as were self- 

 sown seedlings of pois-doux and annatto at one end of the 

 gap. Further experiments of this nature have been insti- 

 tuted. It should be noted in this connexion that cases were 

 observed where cacao trees included with diseased trees 

 within isolation trenches still remained apparently undamaged 

 after a period of several months Opportunity did not 

 permit of full information being obtained as to the experi- 

 ments instituted by Messrs. South and Brooks. So far as 

 could be judged, the application of 'Fungal' has had no 

 beneficial eflFects. Certain of the diseased areas planted with 

 limes had been disturbed; of the plants remaining most 

 were healthy, but some were afi'ected in the characteristic 

 manner: hence there is no doubt that limes are liable to be 

 attacked. Horse beans grown on infested ground were also 

 similarly diseased in part. 



The kola tree (Co^aacumwia^a) mentioned by Mr. Brooks 

 (St. Lucia Report 1912-13) as having so far proved immune 

 must now be included in the list of trees attacked, an 

 example bearing the characteristic mycelium having been 

 found during the visit. 



In viiw of the very susceptible nature of bread fruit 

 and avocado pear trees, the question arose as to whether it 

 is advisable to cut down these trees even when they appear 

 to be healthy. It would certainly be well to be rid of 

 them, and where the planter is prepared to remove the bulk 

 of the roots from the soil it may be to his advantage; but 

 where this is impracticable it is the opinion of the Mycologist 

 that it is better to leave them alone so long as they remain 

 healthy. The living roots probably have some power of 

 resistance to the disease, while the presence of a large mass 

 of dead material in the soil invites its appearance. A number 

 of cacao stumps left in thinning out the trees were examined 



