158 



THE AGRICULTURAL NEWS. 



May 13, 1911. 



FUNGUS NOTES. 



DISEASES OF PINE-APPLES. 

 PART IL 



In an article nbich appeared in the last number of the 

 Agricultural Ktn's, three diseases of pine-apples were dealt 

 with, all of which are due to the fungus Tliielaviojnis para- 

 doxa; in this article it is intended to deal with some other 

 diseases found in Hawaii, and attrilaitable to different organ- 

 isms. These are described in Bulletin 10 of the Hawaiian 

 Sugar Planters' Association, to which reference was made in 

 the last article, and they should be of interest, since the same, 

 or, in some cases, very similar diseases are known to occur 

 in certain of the West Indian islands. 



BEOWN EOT. The symptoms as described by Larsen, are 

 very similar to those of the disease known in Antigua as 

 black heart or core rot. The symptoms of brown rot are as 

 follows (to quote the descrii)tion in the Bulletin to which 

 reference has been made): — 



'Affected pines are, as a rule, quite normal in external 

 appearance. On cutting them open, there will be seen any- 

 where from one to a dozen or more dark-brown patches in 

 the tissue, ranging in size from a small spot to an inch and 

 a half or two inches in diameter. The affected tissue does not 

 become soft and disintegrated, as is the case with soft rot, 

 but remains nearly as firm as the healthy tissue. It lacks, 

 however, the crispness of healthy tissue, and has a somewhat 

 tougher texture. It often occurs just at the base of the flower 

 tubes, in a manner which suggests that this may have been 

 the point of infection. Sometimes that part of the tissue 

 representing one ovary may be involved, while the adjoining 

 tissue is perfectly healthy. The same rot may also infest the 

 fleshy sepals and scales which cover the surface of the fruit. 

 In such cases, it is apparent e.xternally as a brown discolor- 

 ation over the affected area.' 



Stockdale, in a paper in the Wcxi ladinii Bulletin, 

 Vol. VIII, p. IGl, reports a species of Penicillium in conne.xion 

 with the black heart disease in Antigua, and recent investi- 

 gations have shown that a species of this genus is a common 

 saprophyte on decaying pine apple tissue, it may be found on 

 dead portions of the florets, such as the stamens or the remains 

 of the petals. The theory in connexion with black heart seems 

 to be that it is due to this Penicillium, which gains an entrance 

 through Junctures made at the base of the flower tube 

 by mites, or by mealy-bugs, since a species of Pseudococcus 

 (I)actylopius) is of common occurrence inside the ilowers. 

 This theory has not yet been delinitely established; it may 

 however be recorded, that on one occasion during the recent 

 investigations referred to above, fructifications of the Penicil- 

 lium were found in the natural cavity between the flower stalks, 

 underneath an eye which had been damaged by the insects 

 mentioned. 'J'lie tissue of the floret beneath the surface was 

 discoloured dark-brown, and was somewhat soft; the symp- 

 toms were, however, not quite typical of black heart. In 

 Queensland, a species- of Penicillium caused a similar disease 

 of the Smooth Cayenne variety, while on the Prickly variety 



the damage was attributed to a species of Monilia, accom- 

 panied by a mite. In Hawaii, in thirteen out of fifteen 

 cases examined it was found that a species of Fusarium was 

 responsible for the damage; in the remaining two cases 

 a species of Penicillium was found, but in these the 

 affected tissue was decidedly darker in colour than in the 

 other instances. Inoculation experiments showed that the 

 Fusarium obtained from infected fruit tis.sue was able to 

 enter ripe, or nearly ripe, pine apples and produce all the 

 symptoms of brown rot. It would not, however, infect 

 green fruit nearly as readily. Another Fusarium, obtained 

 from the roots, would act in the same manner. Larsen sums 

 up the position in general, as follows: — 



'It seems quite probable, therefore, that several different 

 organisms, when present in the flower tubes, can enter the 

 ti.ssue as the pine ripens and produce a brown discoloration 

 like the one in question. In the brown rot met with in 

 Hawaii, however, it is evident from these cultural studies, 

 that Fu.sarium is the organism most generallj' present.' 



KiPE ROT. This is a disease which only attacks ripe 

 pine.s, and is not of a dangerous nature unless careless 

 methods of harvesting are employed. The symptoms are 

 similar to those of soft rot caused by Tliielavioi)sis, but ripe 

 rot may be distinguished from the latter l>y the following 

 characters, according to the Bulletin: — 



'I. With ripe rot the affected ti.ssue docs not become 

 as soft and as thoroughly disintegrated as is the case with 

 soft rot. 



2. The colour of the affected tissue is lighter and more 

 like that of normal tissue. 



3. The line of demarcation between tlio healthy and the 

 affected tissue is not as distinct. 



4. The black spore formation does not aj)pear when 

 di.seased tissue is exposed to atmospheric conditions. 



•5. An odour of alcoholic fermentation is always 

 present, which is not the case in the earlier stages of soft 

 rot.' 



The disease is believed to be due to an unidentified 

 yeast like organism, but this has not been quite delinitely 

 established. 



SUN sc.vLii. As is indicated by the name, this is a condition 

 which is due entirely to the direct effect of the sun. When 

 pine-apples become bent over for any reason so that one side 

 is exposed to the direct rays of the sun, the upturned surface 

 becomes pale green at first and then gradually turns jsale- 

 yellow. In advanced cases, the epidermis turns brown and 

 becomes dry in spots, while eventually the whole area 

 is brown, dry aiid depressed. A pale yellow border 

 surrounds this area, and this gradually blends into the normal 

 colour of the fruit. The damage often stops at the yellow 

 colour stage. Internally, the tissue beneath the suiiburnt 

 surface is less juicy and cris[) than the normal, and has 

 a decided lack of flavour: while in advanced cases it becomes 

 dry and spong}-. 



Care should be taken to prevent the growth of suckers 

 in positions w here they may push the fruit on one side; if the 

 fruit stalks are bent by the wind or any other agency, the 

 fruits may be jirotected from damage by covering them with 

 hay. 



WILT. This disease often commences with the softening 

 and wilting of the central leaves of young pl.tuts: gradually, 

 all the leaves wilt and the plant dies. In some cases, it is 

 first visible as a change of colour of the leaves from green to 

 reddish or yellow. The roots of affected plants are always 

 dead and filled with the mycelium of a fungus. The cause 

 of this disease has not yet been determined definitely. 



Diseased plants should be removed as soon as they 



