142 



THE AQRICDLTDRAL NEWS. 



April 29, 1911. 



FUNGUS NOTES. 



DISEASES 



OF PINE-APPLES. 

 PAHT I. 



In the last number of the A(/rirultural Nems, .some 

 account wa.s given of the fungus lliidaviopsis jKirado.i-a, 

 which ciiu.ses dise^i.'^i'.s of the jjine-apple, as well as of other 

 host plants. It is proposed to give, in this and a subsequent 

 article, an account of the pine a[)ple diseases due to this para- 

 site, and of certain other diseases of different origin found on 

 pine apples in Hawaii. These are descrilied in Bulletin 10 of 

 the E.xperiment Station of the Hawaiian Sugar Planters' 

 Association. The matter is believed to be of some interest, 

 .as most of these diseases would appear to occur in the West 

 Indies also, more particularly in Antigua, where they have 

 been made the suliject of one or two preliminary investiga- 

 tions; the latest of these was conducted during the pineapple 

 sea.son of last year. This investigation yielded some informa- 

 tion as to the insects commonly found on pine api)les in 

 Antigua, and on their distribution throughout the parts 

 examined. Owing, however, to the fact that the black heart 

 disease, which was that especially under investigation, cannot 

 be detected from the outside of the fruit, and to the fact that 

 this was much rarer in that year than it liad been for some 

 time, nearly all the specimens e.xamined were found to be 

 remarkably healthy. The few unhealthy specimens were 

 attacked by soft rot, or were bruised, while not a single 

 instance of black heart was found. 



FKUIT itoT, To return to the subject of diseases found 

 in Hawaii, the fruit rot or soft rot is undoubtedly the most 

 important, according to the account of them given by L. I ). 

 Larsen in the Bulletin referred to above. This disease 

 attacks ripe pineapples in the field, and occurs at the can- 

 nery to some extent, but is most destructive on crated fruits 

 during shipment. Such fruits, as well as those in store- 

 houses, are often attacked when still quite green. In the 

 field, direct infection usually commences at the base of the 

 fruit. Here a moist chamber is formed between the bracts 

 which occur on the stem, and the base of the pine-apple; the 

 moisture enables the spores of the fungus 7'lti.elavi<ipiiif para- 

 doxa to germinate, and the existence of the chamber prevents 

 them from being killed by the sun. Infection in the field 

 may also occur on other parts of the fruit where there is 

 a wounded .surface. On crated fruit during shipment, the 

 rot commences at the top or on the sides, almost as frequently 

 as at the base. Here again, the presence of wounds favours 

 the entry of the fungus, but, under the dark, moist condi- 

 tions that prevail in this case, the fungus is able to penetrate 

 the fruit directly. This it does especially at points in the 

 cracks between the individual fruitlcts of which the pine- 

 apple is composed. The dry conditions and the destructive 

 effect of sunlight on the spores of the fungus prevent direct 

 penetration of the fiuit in the field except, as already stated, 

 at the base. 



The symptoms of this disease are as follows. The 

 affected tissue has a water-soaked appearance, is of a slightlj' 

 darker shade of yellow than the normal, and has a character- 

 istic odour. It is very soft, even in the early stages of decay, 

 and, as the disease progresses, becomes so disintegrated as to 

 yield to the slightest pressure. The rot spreads very rapidly, 

 and is found to destroy half the fruit in four days from the 



date of inoculation. On cutting open a diseased fruit and 

 exposing the infected tissues to the air, an iinmen.se number 

 of lilack macroconidia of Thielaviopsis is formed, giving all 

 the portion attacked a black appearance. The.se symptoms 

 agree very clo.sely with those of the disease described by 

 Howard on packed pines in Antigua, which was attributed by 

 liim to the macro- and microconidial stages of Trichonplmeria 

 sacchdri, which was then regarded as almost certainlj' iden- 

 tical with Thiilaviojisiit paradoxa. This fungus was found in 

 at least one instance on ripe pine-apples from the same island, 

 in the examination carried out during last sea.son, and referred 

 to above; the symptoms of the rot produced were similar to 

 those observed in Hawaii. 



The wounds which enable the fungus to gain an entry, 

 especially in the field, may be due to sun scald, or damage 

 by animals, or by imjtiements during field operations. One 

 considerable source of injury is that inflicted by in.sects, of 

 which the most important in Hawaii are: a mealy-bug 

 (P.ieii.du<'<>ccii-s /troineliae), a fruit beetle {Carpopliilus humer- 

 alis), vinegar Hies [Drosophila ampelophila and others), and 

 a grasshopper [Xyplddiniii varl/n'ii'nf). It may be of interest 

 to note that a similar mealy-bug {Fseudococcus sp.) is of 

 common occurrence in Antigua on pine-apples; more rarely 

 a scale insect, probably a species of Dia.spis, is found, while 

 different species of mites are numerous; vinegar flies and 

 various grasshoppers are common in the i.slands generally. 



The preventive measures suggested by Larsen are: — 

 '(1) t'utting the fruit with long stems in place of the 

 usual short ones. 



(2) Cutting the fruit bracts at some distance from the 

 stem instead of pulling them off. 



(3) The u.se of straw for packing material, in preference 

 to e.xcelsior (wood wool). 



(4) Wrai)ping the fruit in paper. 



(5) Fumigating with formaldehyde gas.' 



It has not yet been determined if the use of this last 

 reagent on a commercial scale will be practicable, as recent 

 work by Flora W. l'atter.son, of the United States I )epart- 

 ment of Agriculture, referred to in the last article, has shown 

 that a concentration of the gas sufficient to kill the spores of 

 the fungus and to prevent rot, produced a slight change in 

 colour, and loss of turgidity in the fruit. 



BA.sE EOT OF cuTTiNos. This is another disease due to 

 the fungus T/iidaviopsis paradoxa. According to the informa- 

 tion given in the Bulletin mentioned above, it was found in 

 some instances that many cuttings were killed when newly 

 planted out in the field, and that death was due to a rot which 

 had spread through the heart and the underground portion. 

 A gentle pull would remove the diseased plants from the soil, 

 and would often separate the leafy top from the base. Occas- 

 ionally, plants were found to have recovered from a slight 

 attack of the rot. These showed indentations near the base, 

 where the tissues had been destroyed. The disease also 

 occurred on crowns or suckers left in l)ags, or in piles in the 

 fields, and on cuttings during shipment. 



Infection appears to occur principally in two ways, 

 either directly from the fungus present on the surface of the 

 cutting atthetimeof planting, or by means of the mycelium or 

 spores present in the soil. It was found that the disease was 

 much more prevalent \vhen the weather was dry after plant- 

 ing than when it was wet; it may be notetl that the harm 

 done to cane ctittings by the same fungus is much more 

 noticeable in drj' weather than in wet. 



The remedies suggested by Larsen consist of drying the 

 cuttings by placing them butt end upw^ards in the sun for 

 a week; this should be combined with low stripping, that is 

 the removal of as few as possible of the leaves at the base of 



