2o8 DISEASES OF CROP-PLANTS 



disease occurred in July and August, 1918, throughout the 

 colony of Trinidad, where it is now quite general and has put 

 a stop to the development of a lime-growing industry. An 

 attempt is being made to eradicate the disease from the one 

 district in Tobago in which it has appeared. The affection has 

 been longer known as a serious trouble of lime trees in Cuba 

 and Florida, and from accounts seen probably occurs in Jamaica. 

 A severe epidemic results in almost total loss of the current crop, 

 and even a mild prevalence has a marked effect on production. 



Symptoms. 



The fungus does not infect mature foliage or twigs, or fruit 

 after it has reached about three-fourths of an inch in diameter. 

 The attack is made on the young shoots while they are still 

 tender, and on the blossoms and young fruit. Infected shoots 

 commonly dry up at the tip for a distance of an inch or more, 

 or are ringed by an infection further back, and leaves which are 

 infected but not killed have dead areas at the tips or edges which 

 cause them to become distorted in their further development. 

 Young plants in nursery beds are similarly affected. 



On the inflorescences a proportion of the buds have complete 

 petal infestation, turn brown and fail to open ; expanded flowers 

 become infested and fall without setting, and newly set fruit 

 is infested, most frequently by way of the stigma and style, 

 and shed. Infected fruits which are not shed show lesions 

 varying from rounded spots to rough deep cankers occupying 

 nearly half their surface. 



The blossom blight and wither-tip may exist together, or either 

 one may be severe without the other being much in evidence, 

 the difference probably depending on the weather prevailing at 

 the time of greatest susceptibility. In the same way considerable 

 differences appear in fields or plantations not far apart. 



There can be no doubt, from the variations in the incidence 

 of the disease, that it is greatly influenced by weather conditions, 

 but sufficient evidence has not been collected to enable an analysis 

 of the dependence to be made. No influence from cultural 

 conditions has been detected. 



The Fungus. 



The fungus is with difflculty distinguishable from the Gloeo- 

 sporium condition of Coll. glceosporioides, but setae have never 

 been observed. The distinctions indicated by R. E. Clausen 

 are as follows : the acervuli (pustules) in G. limetticolum are 

 flesh-coloured or salmon pink throughout, while those of the 

 other fungus are frequently dark, and on bleached dead spots 

 on leaves and twigs are black. The conidiophores are hyaline 

 throughout their length, and arise from a rather loose stroma of 

 hyaline hyphae, while those of C. glceosporioides are pale sooty 



