196 DISEASES OF TROPICAL PLANTS 



CH. 



A white root fungus has been reported as attacking 

 the roots of the rubber trees of Java and Sumatra. It 

 occurs on trees of all ages, but especially those of from one 

 to two years. The diseased trees suddenly become brown 

 at the top, the leaves become yellow and fall, and the tree 

 dies in from ten to fifteen days after the appearance of the 

 first symptoms of disease. Examination of the roots of 

 the dead trees shows them to be covered with white, 

 leathery, elastic, branching mycelium, and in all prob- 

 ability the tap root was the first to be attacked. The 

 disease is not ordinarily very serious, and the fungus is 

 probably a species of Irpex. Irpex fiavus, Klotsch, is 

 known to be a root parasite on Para rubber in the 

 Straits Settlements. It has also been reported from 

 Java, Ceylon, Queensland, and North America. In 

 Malacca it is said to attack the clove trees, and in the 

 East it has been reported on coffee. 



An undetermined species of Vermicularia has been 

 found to be the cause of a root decay of the Para seed- 

 lings in the Straits Settlements. 



Another undetermined fungus, which has been re- 

 ferred to as a white fungus, causes a disease of the roots 

 of the rubber in the Straits Settlements. It occurs on 

 plants of all ages, but is most severe on those of two 

 years or less, and is first recognised by a browning of 

 the leaves at the top of the young trees. These brown 

 leaves finally fall, and the flow of latex is greatly 

 reduced. Examination of the roots shows the abun- 

 dance of the white fibrous fungus. 



Rosellinia radiciperda, Massee, is a fungus which 

 attacks the roots of Ficus dubia and also many other 

 plants. It appears on the roots as a black, sooty 

 substance and gradually works up the trunk. Like 

 many other root fungi it first attracts attention by 

 causing a dropping of the leaves. 



The fruiting bodies are round, globose, black pustules 

 which are densely covered with small warts. The entire 

 destruction of the diseased plants by burning is the only 

 satisfactory remedy. 



