56 DISEASES OF CROP-PLANTS 



the use of spray fluids is also described by various authors. It 

 would seem that treatment of this kind might be more widely 

 adopted in the West Indies. 



The substance most recommended is copper sulphate in 2.5 per 

 cent, solution, and 0.5 per cent, sulphuric acid is also mentioned. 

 Cooper's Cattle Dip, ij oz. to i gallon of water has been used with 

 success in Trinidad on hibiscus. Trials might be made with 

 strong lime-sulphur sprays. No treatment can be expected to 

 destroy the parasite without also destroying leaves and green 

 shoots, but strengths can be found at which the older twigs 

 will not be seriously affected. 



Love-vine is itself subject to parasitism by more than one 

 species of fungus which occasionally destroy it, but this kind of 

 control, being dependent on special conditions, is not likely 

 to be much extended by artilcial means. 



The crop plant on which love-vine gives most trouble is 

 perhaps the lime, which is liable to become heavily infested. 

 Cacao and cassava are not uncommonly attacked, and the 

 parasite has been reported on sugar-cane. The favourite host 

 of all is the common hibiscus, but there appear to be few shrubs 

 or trees which are not subject to infestation. 



Love-vine is a plant which forces itself on the attention, and 

 as it frequents the borders of highways its presence is noted 

 even by the unobservant. Consequently ^t becomes, like black 

 blight, an object of more public concern than its relative im- 

 portance as a pest can be considered to justify. 



Cassytha. 



A parasite so closely resembling love-vine in habit that it 

 is not usually distinguished from it, though belonging to a different 

 natural order, is Cassytha filiformis L. (Lauracege), which is well 

 distributed but not nearly so common as Culbuta. It may be 

 distinguished in the vegetative condition by its more wiry, very 

 finely striated stems, and its duller colouring of green or greenish 

 yellow. It is more restricted to waste places and bush land. 



Bird Vine : Mistletoe. 



A very considerable number of species of mistletoe 

 (Loranthace£e) are distributed through the West Indies on native 

 and introduced trees. Though they are by no means confined, 

 in most cases, to individual or even related hosts, there is evidence 

 of considerable selectivity in their distribution. 



Unlike the love-vine, the mistletoes are fully supplied with 

 green leaves, but their seeds germinate, not on the ground, 

 but on the branches of trees, and their root system becomes 

 embedded in the wood of the host and draws from it the supply 

 of water and mineral salts which ordinary plants obtain from 

 the soil. In addition to this drain on the sap the heavy masses 

 of leaves occupy space and light to the exclusion of part of the 



