THE PESTS AND DISEASES OF THE CANE. 



Root Fungi. Under this term (Wortel Schimmel) there have been 

 described in Java three fungi characterized by a growth of mycelium under- 

 ground associated with the cane roots ; the first of these was described by 

 Treub as a Pythium, and considered by him as a cause of Sereh ; later work 

 by Wakker did not confirm this identification or connection. Wakker 54 further 

 described two root fungi Cladosporium javanicum and Attantospora radicola 

 as frequently occurring in cane fields but does not 'regard them as parasitic. 

 Of similar habit is the Ithyphallm coralloides stated by Cobb to be the cause of 

 a root disease in Hawaii ; later work has not confirmed Cobb's views on the 

 parasitic nature of this fungus, though some evidence exists that the under- 

 ground mycelial strands interfere to some extent with the development of the 

 cane roots. In the Hawaiian islands it is a matter of common knowledge that 

 the Ithyphallus is often abundant on the most productive fields. 



The Control of Fungus Diseases. 



1. Use of healthy, selected, disease-free seed for planting. This can 

 be effected by careful selection, or by growing seed cane in nurseries 

 remote from infected areas, or by using for seed cane from that part 

 of a plantation which is observed to be the least disease affected, and rigidly 

 rejecting for seed purposes any cane from parts of the plantation that are 

 known to be infected with disease. The presence of red fibre is, according to 

 Cobb, a sure sign that the cane is not disease free. 



2. Use of fungicide wastes on the seed. The exposed ends of cane 

 cuttings form a most convenient point of entry for fungus spores, particularly 

 the Thielaviopsis ethaceticus, and it is this organism that is largely responsible 

 for the non-germination of cuttings and the consequent expenses of 

 ' supplying.' It has been shown by the experiments of Howard in Barbados, 

 of Cobb in Hawaii, and of others, that soaking the cuttings in Bordeaux 

 mixture preparatory to planting is a very efficient prophylaxis. 



Bordeaux mixture is prepared as under : 



Dissolve 6lbs. crystallized copper sulphate in 25 gallons of water. 

 Slake 4 Ibs. of quick lime in 25 gallons of water. 



Gradually add the lime water to the copper solution, with constant 

 stirring ; when completely added, test the mixture by immersing in it for a few 

 seconds a bright steel blade ; this should not become coated with a red layer 

 of metallic copper ; but if the blade becomes coated more lime must be added. 



The time during which the cuttings should be left to soak is half an hour. 



In addition to soaking in Bordeaux mixture, the protection of the cut ends 

 with tar has been proposed. 



3. Isolation of diseased areas and patches, and destruction of fungus in 

 these areas by heavy dressings of quicklime. This was recommended by 

 Howard, Lewton-Brain, and Cobb, in connection with the various root fungi. 



4. The adoption of all means likely to result in a diminution of flies is 

 also recommended by Cobb, as he has shown how these insects are responsible 



155 



