174 



THE AGRICULTURAL NEWS 



Mai 22, 1915. 



FUNGUS NOTES. 



PRELIMINARY NOTE ON A DISEASE OF 

 CARICA PAPAYA. 



Opportunities have recently occurred oi exami 

 specimens exhibiting whal appears to be well-mat 

 disease of the papa\i tree. 



The writer has seen from time to time in Barbados 

 instances of a localised stem rol oi the papain A widei 

 depression or shrinkage is produced; the wound becomes 

 infested with bacteria and with 9; and beetl larvae, and 

 usually leads to the falling over of the top. 



A young tree which recently b eased in the 



garden of the Commissioner of Agriculture afforded an 

 example of a fairlj advanced stage oi what •• i ired t" be 

 the same affeci 



In a regi i i he stem sil nated at about three qu irters 



ol its total height above the ground, just at the base of its 

 green portion, there occurred a browning oi the tissues, 

 accompanied t-y a very distinct shrinkage in the circum- 

 ference of some 6 "i' 8 inches of it. length. The 

 leaves showed signs of failing, and had extensive d 

 ami browned areas. A fully grown but unripened fruit 

 had a diseased area on one side. The small, closely 

 grouped pustules of a fungus were found abundantly in 

 connexion with each of these lesions. On the leaves the 

 pustules were surrounded by black bristles, and were those of 

 a typical Colletotrichum, on the stent and fruit the bristles 

 were absent. The spores were identical in form and origin 

 in all three situations. Typical examples measured L6-17"5 

 by tT-4"8 microns. The absence in particular circumstances 

 of the characteristic bristles is familiar amongst species of 

 Colletotrichum, and does not reduce the probability of the 

 identity of the form found on the stem and fruit with that on 

 the leaves. 



In Angust 191 I Mr. W. Kobson, Curator of the Botanic 

 Station, Montserrat, forwarded for examination specimens of 

 diseased pa paw fruits and stems, reporting that the disease 

 had been noticed on papaws in Montserrat for a considerable 

 time, but was particularly prevalent at the time of writing 

 in the neighbourhood of Plymouth. He went on to say that 

 the disease appears to commence on the fruit as a water- 

 soaked area which after a time becomes sunken and later 

 blackens: ultimately the fruit rots altogether. The disease 

 on the stems also commences as a water-soaked area. In 

 some cases the stem is entirely girdled and the top breaks 

 other rases recover to a great extent. 



The stem material sent was not in good C lition, being 



old; the only fungus detected was a species of Phoma. 



Ala -"i t, consisting oi several examples of early 



water-soaked Lesions, some only just beginning, showed 

 throughout a fungus apparently identical with that on tic 

 Barbados specimens. Satisfactory material of the fruit 



disease has not yef be iceived from Montserrat. 



I'm : nil- of a Coll i a, which is prob i ime 



, have I ob erved to be common on the petioles oi 



the old and dying leaves "t healthy trees. Tests of the 



sitism of the fungus and of the identity of the 



two forms are projected. 



w.\. 



DISEASES OF CASSAVA IN TRINIDAD. 



Am. mgst a eollei i printed in the 



' it of Agriculture. Trinii 



1915, occurs an account of the fungous diseases of that plant 

 bj Mr. .1. B. l; 



Tlie author states that in Trinidad cassava has been 

 remarkably free from such troubles, presumably because 

 the plant has been grown onlj in a discontinuous fashion. 

 The adoption oi cassava as a regulai crop owing to the 

 demand from the three factories now at work in the island 

 will doubtless give greater opportunities for disi a-es to assert 

 Ives. 



The only diseases mentioned as occurring in Trinidad 

 two leaf spot affections. < >ne of these, in which the spots 

 are onlj ,'. to inch in diameter, white in colour, and 

 surrounded by a brown or purple border, does little damage. 

 The other, which produces brown -pots [ to |-inch in 

 diameter, often -.. numerous that they coalesce, may destroy 

 a considerable area of leaf, and causes many leaves to fall 

 prematurely. A spraying experiment is being carried out in 

 order to ascertain the amount of economic loss, if any, pre- 

 ventible by this means. 



Reference is made to diseases occurring on cassava in 

 other parts of the Tropics. These include leaf .■ to- 



Gercospora spp., hat and stem diseases due to Gloeosporii 

 manihotii, and a stein disease due to Bacillui manihotus. 



To this it may he added that in the Lesser Antilles 



cassava is liable to he attacked an. I killed by the Rosellinia 

 ro,,t disease of cacao when planted as a cover crop on areas 

 from which the trees have died from this cause, and that 

 a Gloeosporium die hack and a bacterial leaf disease occur in 

 Barbados. 



ROOT DISEASES IN MALAYA. 



Two root diseases of Hevea in the Malay States are the 

 subject of article^ by Mr. F. T. Brooks in the Agricultural 

 ' Bulletin, Vol. Ill, Nbs. 2 and 3. 



The disease caused by Sphaerostilbe repens is of interest 

 in the West Indies because of the attribution of the red rout 

 disease of limes in Dominica to a member of the same genus. 

 The disease as it occurs in Ceylon has been already des- 

 cribed by Mr. T. Fetch. 



The progress of the disease is .slow. Its effects are seen 

 above ground in the thinning of the foliage and the gradual 

 dying hack of the branches. There is n,, external mycelium, 

 hut characteristic Hat strands occur between the bark and 

 the wood of the roots. They arc about | inch across and 

 vary from grey to dark-brown or black. The finer mycelium 

 permeates all puts of the bark and wood of the affected 



Organs. The disease progresses from the lateral roots to the 

 collar, and may ascend some distance up the trunk. Fine 

 trees fifteen to twenty years "Id an- affected, as well as 

 younger specimens. The distribution is usually a scattered 



The fungus exists as a saprophyl i dead material, 



hut in the disease, 1 trees it is found advancing into living 



tissues and th ng as a parasite. The means and 



' DiptS to infect 



v. ith pure cull lul. 



The Usual t. a dealing with root diseases are 



amended. 



The se,-., tl , I ,j .,,...,■ j , : . , not been previously recorded in 

 Malaya, and tl ivefungushas r»< itified "ith 



certainty. It is similar to, an. I possibly identical with, 

 /'.// dim i '.onata, which, as in the case of the fungus men 

 tioned above, has i 'etch as gi 



of ] levea and other plan's n ( Jeylon. 



The collar i- the part of the tree principally affected. 

 'The frnit-bod like in form, greyish brown in 



