14 



THE AGRICULTURAL NEWS. 



Jaxi AP.v 3, 1914. 



FUNGUS NOTES. 



FOMES 



SEMITOSTUS 

 GUIANA. 



IN BRITISH 



BLACK SPOT OF ROSE LEAVES. 



Besides one or more root diseases, there occur on rose 

 bushes grown in West Indian gardens two leaf diseases 

 which give some trouble. These are the rose mildew and 

 the black leaf spot. The former was dealt with at some 

 length in the Agriciiltnral News (May 25, 1912) so that it 

 need only be repeated that the simplest remedy consists in 

 dusting the leaves with a mixture of 2 parts by volume of 

 flowers of sulphur with one part of quicklime, applied when 

 the leaves are damp. Sunshine is necessary to generate the 

 effective gas or gases from the mixture. 



The black spot disease is less noticed, but is very 

 common. It varies considerably in the severity of its 

 attack. Some traces of it may be found almost at any 

 time, and the leaves very often develop it when senescent, 

 without much harm being done to the plant. It is capable, 

 however, of becoming epidemic and doing much damage by 

 causing repeated premature leaf fall and thus impoverishing 

 the plant. 



On their first appearance the spots are brownish in 

 colour, later thej- become shining black, and still later the 

 central portion turns grey or brown. They vary from about 

 l^-ineh to nearly A-inch in diameter. The spores are devel- 

 oped in tiny black pycnidia scattered about in the spots. 

 The mycelium of the fungus is largely subcuticular, and 

 a fairly reliable diagnosis of the disease may be maJe by 

 noticing with a lens the raised radiating lines which mark 

 the course of the hyphae. 



The first essential of treatment is the collection of 

 diseased leaves, especially those which have fallen from the 

 plants. By this means alone a very considerable diminution 

 of the disease may be obtained. It should, however, be 

 supplemented in the case of serious epidemics by spraying 

 with a fungicide about once a week until the leaves bearing 

 the spots have all been replaced by healthy foliage 

 Bordeaux mixture may be used with safety on most varieties 

 of roses if applied in a fine spra}-. To avoid the trouble 

 of mixing small quantities of Bordeaux mixture, or to 

 avoid damage to delicate varieties, ammoniacal copper 

 carbonate may be used instead. For this fungicide 1 oz. of 

 copper carbonate and about ipint of ammonia are used in 

 preparing 8 gallons of the spraying solution. Rub up 

 the copper carbonate into a paste with a little water, dilute 

 the ammonia with four times its volume of water and dissolve 

 the copper carbonate in it by stirring. It is better to leave 

 a little undissolved than to have any excess of ammonia. 

 Make up to 8 gallons with water. The solution should 

 be used quickly after being made because of the rapid loss 

 of ammonia. Copper carbonate may be prepared from copper 

 sulphate by mixing a solution of 10 lb. of copper sulphate in 

 10 gallons of water with a solution of 12 Bb. of washing soda 

 in an equal amount of water, then washing and drying the 

 precipitate which settles out. 



It is stated in the Bulletin of the Department of Agri- 

 culture of Trinidad and Tohago, that in connexion with 

 spraying for bud rot (of coconut trees) no definite results 

 have been obtained as only two unsprayed trees in the area 

 selected had died, but the yield from the sprayed trees 

 seemed to be greater. The sugar birds did not pick the 

 flowers from the sprayed trees, which in some measure 

 accounted for the greater yield of the sprayed trees. 



The following note by the tJovernment Botanist, 

 British Guiana (Mr. C. K. Bancroft, JM.A.), is taken 

 from the Journal of the BosltcI of Agriculture of that 

 Colony, for October 1913:— 



During a recent visit to the interior of the Colony the 

 writer observed fructifications or 'brackets', as they are 

 popularly termed, of Foines sei/iitoslus on a stump of a dead 

 tree (species not known) on a trail leading from Tumatumari 

 to Konawaruk. The brackets were identical with those 

 which occur in the East, possessing dark and light brown 

 zones on the upper surface, a yellow margin or lip and 

 a bright orange-coloured under surface. 



This fungus, which is the cause of the common root 

 disease of cultivated Para rubber, is a parasite of consider- 

 able economic importance. Its occurrence in the Western 

 Tropics has not to the writer's knowledge been recorded 

 before, and would indicate a much wider distribution of the 

 fungus than has previously been thought to occur. 



Its occurrence in South America is of more than individual 

 interest in that it adds another to the list of parasitic fungi of 

 economic importance which are freely distributed in theTropics. 

 Some of the fungi are Pliytophthora laheri, the cause of the 

 pod disease and canker of cacao, Thyridarin tarda, the die-back 

 of Hevea and cacao, Jlarasmius sacchari. the root fundus of 

 sugar-cane, Hi/menochaete noxin, the cause of a root disease 

 of Hevea and cacao. These rank amongst the most important 

 parasites which the cultivator has to deal with in the tropics at 

 the pres-ent day. And as the work on plant diseases in the 

 Tropics progresses it is possible that a far wider distribution of 

 parasitic fungi will be shown to occur than is indicated at 

 present. To what extent they may have been introduced from 

 one country to another, or to how far they can really be re- 

 garded as native to the countries in which they now occur it 

 is not possible to determine; but the fact that several of the 

 most important fungi which are parasitic on cultivated 

 plants in the Tropics appear to possess such a wide geograph- 

 ical distribution is worthy of mention, in view of the quaran- 

 tine regulations now being enforced by many tropical 

 countries. 



Other 'bracket fungi' commonly seen in the East on 

 dead wood, which were recorded during this visit, were 

 Pohistirtus sanguineus and Schizo23hi/llum commune. 



THE SOIL 



THE GASES OF SWAMP RICE SOILS. 

 The cultivation of paddy in Southern India in- 

 cludes amongst other things, the maintenance of 

 swamp conditions, the puddling of the soil (thereby 

 decreasing the natural drainage) and the use of large 

 quantities of green manures. These circumstances 

 must make the soil conditions and the nutrition of the 

 plant very dissimilar to that which occurs in the case 

 of ordinary soils. 



Hence the study of the gases in these soils was 

 thought likely to lead to important results. The 

 following are the conclusions drawn as the outcome of 

 such study by W. H. Harrison, M.Sc, and P. A. 

 Sabraniania Aiyer, B.A., of the Madras Department of 

 Agriculture: — 



