12G 



THE AGRICULTURAL NEWS. 



April 15, 1911. 



FUNGUS NOTES. 



THE FUNGUS CAUSING PINE-APPLE 

 DISEASE. 



The history of the fungus causing the well-liiiown pine- 

 apple disease of cane cuttings is somewhat interesting, 

 and contains at least one curious coincidence. Moreover, 

 recent work has shown that it is an organism of very consider- 

 able economic importance, as its range of host plants 

 includes at least two other valuable crops besides sugar-cane, 

 namely pine-apples and cocoa-nuts. Another point that en- 

 hances its economic importance is its extensive distribution 

 throughout almost all tropical and some subtropical countries. 

 It occurs chiefly on sugarcane in India, Java, Hawaii, 

 Mauritius and the West Indies, on pine-apples in Hawaii and 

 the West Indies, and on cocoa-nuts in Ceylon and Trinidad. 



The peculiar coincidence connected with its popular 

 name began with its discovery on pine-apples in France by 

 de Seynes in 1886; the scientific name then given to it was 

 .SjMruchisma jJaradoxum. In 1893, Went made an indepen- 

 dent discovery of it on sugar-cane in Java and on account of 

 the smell of the infected tissues, called the disease which 

 it occasions the pine-apple disease of sugar-cane. At the 

 same time he gave the fungus the name Thielaviopsis 

 ethaceticus. In 1901 Howard found this same fungus* causing 

 a rot of shipped pine-apples in Antigua, but the result of his 

 investigations was not published until 1907, when it appeared 

 embodied in a iiaper by Stockdale ( West Indian Bulletin, 

 Vol. VIII, p. 162). In 1904 von Hohnel found de Seynes's 

 fungus on a cocoa-nut in Austria, and on comparison with 

 Went's description, came to the conclusion that Sjyorocliisina 

 paradoxum and Thielaviopsis ethaceticus were the same. 

 This opinion was confirmed by Went himself, and since 

 his generic name appeared the more suitable, the fungus 

 became TIdelaviopisis parado-ca. In 1907 Cobb found it on 

 pine-apples in Hawaii, and recent work by L. D. Larisn, 

 published in Bulletin 10 of the Experiment Station of the 

 Hawaiian Sugar Planters' Association, has resulted in a clear 

 understanding of its effects on that host. Thus the fungus 

 best known as that causing pine-apple disease of the sugar-cane 

 has been found to cause serious diseases of the true pine-apple. 

 Another recent publication dealing with the efiect of this 

 fungus on pine-ap[)les is Bulletin No. 171 of the Bureau of 

 Plant Industry of the United States Department of Agricul- 

 ture, by Flora W. Patterson, Vera K. Charles and Frank 

 J. Veihmeyer. This treats of the effect of fumigation with 

 formaldehyde gas in killing the spores of the fungus. 



Two important papers on this fungus were published 

 by Petch in 1909 and 1910, which dealt with its efiect on 

 cocoa-nuts, and with various other points, such as its life- 

 history, and the action of various poisonims substances in pre- 

 venting the germination of its spores, or in causing their death. 

 The first of these appears in the Circulars and A;/ricultural 

 Journal of the Roytd Ikitauic Uardens, Ceylon, Vol. IV, 

 No. 22. The second was published in the Annals of the 

 Royal liutanic Gardens, Peradeniya, Vol. I\^, p. 511. 



liefore proceeding to an account of the fungus, it may be 

 worth noting that a general recognition by agriculturists of 

 the fact that this fungus could occur on pineapples in the 

 West Indies has probably been to some extent obscured by 

 the use of the name '/'richosphaeria sacchari for the parasite. 

 The reason is that Massee, m investigating the life-history of 

 the .so-called rind fungus of the sugar-cane, found forms of 

 spores which appeared identical with the spores produced by 



* Described by him as the endoconidial stage of Trkhos- 



phrteria sacchari. 



the pine-apple disease fungus, and in consequence put forward 

 the theory that these two fungi were in reality identical. This 

 view was long held in the West Indies, but the balance of 

 recent evidence is certainly opposed to it; and it seems now 

 to be much more probable that the cane stem fungus, Tri- 

 chosphaeria sacchari, and the pine-apple disease fungus, 

 Thielaviopsis paradoxa, are quite independent of one another. 



The pine-apple disease of sugar-cane is too well known 

 to require description here, and the .symptoms of the stem 

 bleeding disease of cocoa-nut trees have been described in the 

 Agricidtural News, Vol. IX, p. 255, and elsewhere. Three 

 diseases of pine-apples are known to be due to this fungus in 

 Hawaii, namely, fruit rot, or soft rot of the fruit, which is 

 the same as that reported from Antigua, base rot of cuttings 

 and leaf spot. The Antigua disease referred to, is not that 

 known as black heart. 



The fungus produces two forms of spores, microconidia 

 and macroconidia. Difterent authors give somewhat varying 

 accounts of their appearance and method of formation; 

 the following is taken from that given by Petch. The 

 microconidia are smaller than the macroconidia, they are 

 colourless at first and almost exactly rectangular in shape; 

 subsequently, they become oval and darker in colour until 

 they are greenish black. In some instances, especially when 

 removed to some distance from the mycelium, the colour 

 change occurs very slowly. The microcondia are produced 

 ■ inside a long, narrow hypha which is somewhat swollen at the 

 base. They are formed one after another, and are extruded 

 from the hyphae, as they are formed, in long chains contain- 

 ing from twenty to eighty of the spores. The macroconidia 

 are larger; they are usually oval or pear-shaped, and when 

 mature are greenish or brownish black in colour. Like the 

 microconidia they are formed inside a hypha and are extrud- 

 ed; but in this case the hypha is shorter than that giving 

 rise to microconidia; the process of formation occupies more 

 time; and only about twelve macroconidia are produced. 

 Unlike the microconidia, the macroconidia will not germinate 

 in water. When either of these spores is sown in a nutrient 

 medium, it will germinate readilj', and give rise to a mycelium 

 which produces microconidia first and then macroconidia. In 

 the decaying tissues of sugar-cane or cocoa-nuts, only macro- 

 conidia appear to be produced. 



In addition to the plants already mentioned, the fungus 

 can live upon ripe mangoes and bananas, while Petch has 

 shown that it does not survive on parts of the cocoa-nut plant 

 which do not contain sugar. This led him to suggest that 

 the growth of the fungus is dependent upon the presence of 

 sugar in the substance upon which it is living. Another 

 interesting point has been shown by Larsen, who carried 

 out an experiment to prove that the fungus can live 

 on decaying vegetable matter in the soil at a depth of at least 

 2 inches lielow the surface. This throws some light on 

 its power of attacking sugar cane and pine apple cuttings. 

 Petch showed that the fungus will grow much more vigor- 

 ously in the dark than in the light. Drought and sun- 

 light will in some instances kill the spores in seven days; 

 while in others as much as seventy days is required. 

 Larsen, in Hawaii, found that during the summer the spores 

 growing in liquid media were killed by a few hours' exposure 

 to direct sunliglit, and that even when growing inside a cover- 

 ing of pine apple tissue a quarter of an inch thick, both spores 

 and mycelium were killed by twenty-four hours' exposure to 

 sunlight. 



Some other interesting points connected with the fungus 

 will be dealt with further, in a subseijuent article in the Aari- 

 cultural Nen-s, and in this the diseases of pine-apples will also 

 be described. 



