February 1, 1917.] 



THE INDIA RUBBER WORLD 



297 



FIGHTING THE LEAF DISEASE IN DUTCH GUIANA. 



IN his report on the South American leaf disease (as briefed in 

 The India Rubber World, September 1, 1916, page 689), Mr. 

 Bancroft recommends spraying with a solution of sulphate of 

 copper in lime water. He also advocates the destruction, by bury- 

 ing or burning, of all fallen leaves. 



A preliminary report of Dr. G. Stahel, Government Mycologist 

 •of Dutch Guiana, has been made which takes a somewhat dis- 

 similar view of the efficacy of spraying, and recommends radically 

 different treatment for eradicating the disease. 



Dr. Stahel has completed his investigations, but the Board of 

 Agriculture is delaying the full report until drawings and photo- 

 graphs, which are to be reproduced in Holland, are available. 

 However, the preliminary report has been published in order that 

 practical work may not be further delayed. This report is as 

 follows : 



The disease is attributable to a fungus of three fructifications. 

 The main fructification, i. e., the perithicium, is found on the 

 ■old leaves, in one to two months at its earliest and before they 

 are matured. 



The pycnidium fructifications are always observable on the 

 matured leaves ; after two months the perithicium always pre- 

 dominates and is always to be found on the leaves. 



The scolicotrichum conidium buds in water in about two 

 hours ; if sowed on young leaves, it will be found that after ten 

 hours, a large percentage of the germ-tubes collect under the cu- 

 ticule, and after 20 hours they will penetrate between the epider- 

 mis cells into the leaves and branches. 



Drying the conidium, they will die out after IS hours. The 

 pycnospores bud in water and in nourishing solution, after a few- 

 hours, but the general germ-cell does not exceed two to three 

 micron in length. 



Sowed on very young leaves, the germ-cell will not develop 

 further. 



The ascospores bud in about the same period as the scoli- 

 cotrichum-conidium sowed on young leaves. It will be found 

 under the cuticule after 12 hours, very few, single and short germ 

 cells, but after 20 to 22 hours these germ cells will be found far 

 thinner than the scolicotrichum, although grown a little further 

 under the cuticule, but not penetrated in the leaves between the 

 epidermis cell ; if the spores are dried out they die in a few 

 hours. The production, however, of ascospores is further very 

 limited, even when the leaves are well supplied with much peri- 

 thicia. but few on some of the trees that I could obtain for my 

 investigation. 



The ascospores will, therefore, contribute very little in spread- 

 ing the disease. Tlie matured leaves, which so far only bear 

 perithicia are consequently not very dangerous. 



It is, however, with the young and matured leaves quite dif- 

 ferent ; these produce a large quantity of scolico. We have 

 found in Hevca fields trees that were withering during the 

 •whole year, or trees which were forming young sprouts invested 

 with scolecotrichum fructifications. In view of these facts 

 we have come to the following conclusions : 

 _ Care should be taken during three to four weeks that the cul- 

 tivations be kept free from all young Heziea leaves, and it will be 

 found that all scolecotrichum fructifications will disappear and 

 also the conidium within 24 hours. The scolecotrichum fructifi- 

 cations will appear again, however, at a later period, and will 

 spread, if the ascospores be not effectively made harmless. It will 

 be necessary, therefore, from time to time to repeat the treat- 

 ment ; but experience will teach in the interval between each 

 treatment. 



_ It is obvious in these treatments that the neighboring planta- 

 tions follow suit, or in the event of unwillingness on the part of 

 the neighbors to do so the Hevea trees should then be removed 

 from the fields. 



As the leaves of the Hcvea always form in a cluster from, say, 

 eight to ten, close upon each other, at the end of the branches, 

 they can be cut off very easily with the aid of a cocoa knife, 

 which is to be highly recommended. 



For instance, during the dry season, when the latex is not 

 flowing sufficiently, the laborers can be divided for a few weeks 

 and put to work in the Hevea fields to destroy all the young 

 leaves, especially at certain times, when only small portions of 

 the trees are wintering or producing new sprouts. A laborer can 

 treat two large or three small ones in a day of eight hours. 



Whether this mode of fighting the disease in Dutch Guiana 

 will prove effectual if continued is hard to say, or whether it 



would be better to substitute the Hevea in the coffee fields by 

 coffeemama trees I refrain from discussing. 



Until recently I have overvalued the significance of ascospores 

 for spreading the disease ; only by the latest investigations dur- 

 ing the last two months it has proven to me that the infective 

 power of tlie ascopores can be insignificant, and only in view of 

 these results could I recommend a method which, to my idea, 

 will prove technically adequate. 



A few weeks back an article appeared in one of the local 

 papers to the effect that in British Guiana something had been 

 effected towards the eradicating of the disease, and in conse^ 

 quence I am obliged to mention something in connection with 

 the system employed in that colony. 



It is recommended by the Government botanist in that colony 

 that spraying the young leaves with Bordeaux mixture and cut- 

 ting off the dried branches from the healthy parts and destroying 

 the fallen leaves will be found to help remove the disease ; to 

 this I will say dead fungus does not do any harm. But the 

 cutting of the dry branches from the healthy part is based on the 

 fact of my investigation and which I cannot even recommend. 

 I have, therefore, advised a few plantation owners where the 

 system has been carried on not to continue it ; the reason of this 

 will appear in the Bulletin. 



Spraying of the 'trees with Bordeaux mixture will, when 

 applied on leaves two to four days old prove favorable, but the 

 application appears to me for various reasons to be unfit ; in the 

 first place, it is expensive and not so beneficial as my proposed 

 method. 



Proofs are also shown here that the young leaves of one to 

 three centimeters cannot bear the spraying with Bordeaux mix- 

 ture, and will curl and fall off. This fact has also been proved 

 on the Slootwijk plantation during the fighting experiments. 



It will thus be seen that these two investigators are widely at 

 variance regarding the methods necessary to overcome this dis- 

 ease. However, we understand that Mr. Bancroft has not yet 

 completed his investigation, and moreover, has since made a visit 

 to Dr. Stahel to consult with him regarding this important matter. 

 It is hoped that as a result of this meeting conclusions will bt 

 reached which will be of such character as to provide rubber 

 growers throughout the world with a remedy for this formidable 

 disease. 



CRUDE RtJBBER IN HONDUHAS. 



According to the American Consul at Ceiba, Honduras, the 

 crude rubber industry there is dormant. The low prices pre- 

 vailing in rubber markets, coupled with the export duty levied 

 by the Government of Honduras and the municipalities, amount- 

 ing at Cuba to approximately 4 cents gold per pound, makes 

 rubber gathering so unprofitable that the natives will not tap 

 the trees even when they can find them close at hand, and traders 

 declare that they buy the product merely as an accommodation. 



RUBBER TRADE OF BOLIVIA IN 1916. 



According to the .statement of the Bolivian Minister of Fi- 

 nance to the 1916 National Congress of Bolivia, the exports of 

 crude rubber, which amounted to 4,484,915 kilograms [9,867,813 

 pounds] in 1914, reached 5,034,847 kilograms [11,120.663 pounds] 

 during the fiscal year 1915-16. 



RUBBER GOODS IMPORTS INTO VENEZUELA. 



The .American Consul at Maracaibo reports the following im- 

 ports of rubber manufactures into Venezuela during the years 

 1914 and 1915: 



Tires. All other rubber goods. 

 A A 



From — 1914. 1915. 1914. 1915. 



United States $1,720 $5,600 $1,320 $3,152 



United Kingdom 490 1.200 



Germany 1,960 



All countries $1,720 $5,600 $3,770 $4,352 



CONSULAR INVOICES FOR BRAZILIAN SHIPMENT. 



The Brazilian budget law for 1917 provides that no invoices 

 after shipment will be accepted by Brazilian consuls, and ship- 

 ments unaccompanied by consular invoice pay double duty. 



