THE PALMS OF BRITISH INDIA AND CEYLON. 337 



It has a width in its widest part of abo\it 30 miles. This area 

 ■coincides pretty closely with the area of heaviest rainfall, the rainfall 



ranging between approximately 100 inches and 300 in a year 



By far the greater part of the rain falls betAveen the months of 

 June and September and it is during this time that Koleroga is 

 prevalent in Mysore." The disease has, besides, been reported 

 fi'om North Kanara, South Kanara, from a small tract in Malabar 

 adjoining Cochin State and from Cochin State itself. Mr. Butler 

 informs me that lately the disease has also spread to Dharwar. 



" The disease ' Koleroga ' usually makes its first appearance to- 

 wards the end of June, about two or three weeks after the begin- 

 ning of the rains. It restricts itself for the most part to the nuts 

 themselves, but occasionallj^ passes over into the tops of the palms 

 in which case they very speedily succumb. The nuts soon after 

 they are attacked begin to drop from the trees and it is this drop- 

 ping of diseased nuts which signals the advent of the disease to the 

 garden owners. Its spread is usually remarkabl}^ rapid so that 

 within a few weeks an area of many acres may have become badly 

 infected." 



The cause of this disease is a fungus belonp-ing to the o-enus 

 Phytoplitliora. To Coleman it seems rather doubtful whether this 

 fungus should be considered as a distinct and new species. He 

 finally decides for placing it with Phytophthora omnivora, but as a 

 •distinct variety, viz, var. Arecce until such time as he will be able 

 -"■ to make a thorough search for alternate host plants and until the 

 different omnivora forms have been carefully investigated. " This 

 fungus has since been raised to the rank of the species : rhytophthora 

 Arecce (Col.) Pethy. 



The owners of betel-nut gardens have themselves invented a 

 method of protection against the disease. They cut covers made of 

 the basal sheaths of the big leaves and tie them over the bunches so 

 as to protect them from the rain. This method is not very satisfac- 

 tory and the disease may under certain conditions be favoured rather 

 than checked by the coverings. Coleman thought that sprajang 

 with Bordeaux mixture might prove successful. The resailts of a 

 year's spraying which he collected and published show that he was 

 not mistaken. 



According to MoUison, a borer does considerable damage to the 

 betel-nut palms. " It cuts a tunnel from the root upwards and in 

 time reaches to the growing top. The damage there done is so 

 considerable that the top withers and when -s^'ind blows breaks oft 

 •and falls to the ground. " 



Of Godavari, it has been said that termites oiten injure the palm 

 materially by eating the rootlets (Watt). 



Illustration. — Plate LXXXI shows a group of Betel-nut Palms 

 taken by Mr. Macmillan in the Botanic Gardens of Peradeniya. 

 18 



