1932.] NOTES ON PROCLAIMED DISEASES AND PESTS. 179 



ANTHRACNOSE (BLOSSOM-BLIGHT AND WITHER-TIP) 



OF LIME. 



This highly infectious fungus disease occurs on the lime (both 

 common and spineless) and on some varieties of lemon. No other Citrus 

 species or other plant is known to be susceptible. Infection is confined 

 to the young and tender organs of the plant, i.e. the tips of new shoots, 

 buds and flowers, and recently set fruits. The parts attacked are mostly 

 killed. The leaves which survive and develop on the infected shoots 

 show more or less deformity due to the injuries received in the tender 

 state, and fruits which survive infection show large or small corky spots 

 or cankers for the same reason. 



I 



The causative organism is the fungus Gloeosporium limetticolum 

 Clausen. Its one-celled oblong spores form a pinkish coating on the 

 affected parts and are probably distributed by air currents, rain, birds 

 and insects. There is evidence which seems to show that infection has 

 been carried from one district to another on full-grown lime fruits. 



The disease is generally distributed over Trinidad, and even exists 

 on an isolated tree on the highest point of the island of Chacachacare. 

 In Tobago it has apparently been present for some years, confined to one 

 isolated plantation, but has recently escaped from this situation and 

 begun to spread rapidly in its neighbourhood. The disease has been 

 proclaimed for the purposes of an attempt at eradication in Tobago. 

 There is nothing to be gained by action under the Ordinance in Trinidad. 



As regards other countries the disease occurs in Bi-itish Guiana, is 

 well-known in Cuba and Florida, and from accounts seen maybe present 

 in .Tamaica. It has not so far been found in other islands of the Lesser 

 Antilles, and no limes or lemons from Trinidad should on any account be 

 sent there or to any tropical country. 



It is possible to control the disease by spraying with Bordeaux 

 mixture or preferably lime sulphur solution at the times when a flush of 

 new growth or blossom takes place. The habit of the lime is so irregular 

 in this respect that frequent applications are necessary for full 

 protection, and the value of the produce is too small to cover the cost of 

 materials and labour. 



A theory has been put forward based on some local observations that 

 the losses from the disease are greatly reduced by the provision of 

 shade trees. Against this must be placed the fact that in cnses seen of 

 limes planted fairly extensively among cacao and between rows of 

 coconuts the influence of the disease has been exerted to the full. 



The only visible hope of establishing a citric acid industry in the 

 Colony in the presence of this disease lies in the search for immune 

 varieties. An Indian lime is at present under test, and seeds of other 

 varieties have been obtained with due precautions from the Philippine 

 Islands. One of these is stated to be immune to ' wither-tip,' but it is 

 not known whether the fungus concerned is identical with ours. 



