CHAPTER XIX 



DISEASES OF LIME AND OTHER CITRUS TREES 



There are distinct differences in the resistance offered by the 

 various citrus species to dry conditions. In the lowland dis- 

 tricts of Barbados, for example, the lime, the shaddock, and the 

 rough lemon can exist, though they cannot be said to thrive except 

 under very sheltered conditions. The mandarin will grow and 

 flower but rarely sets fruit. The grapefruit and the orange only 

 exist, and that somewhat precariously, in a few sheltered spots in 

 the wetter uplands. 



In Dominica and St. Lucia, on the other hand, the lime is 

 thoroughly at home, and other citrus fruits do proportionately 

 well. The sweet orange, however, is limited in duration unless 

 it is grafted on sour orange stock, by the development of gummo- 

 sis of the collar at the age of about 25 to 30 years. Two extremes 

 of habit can be recognised in the lime as grown in Dominica. 

 In exposed positions or on poor or water-logged soil, growth is 

 slow and " hard," the leaves are smaller and stiver, the foliage 

 is scanty and greyish green in colour. On rich and deep soil 

 with good drainage and shelter, growth is vigorous and rapid, 

 the leaves are large and thin, the foliage is heavy and very dark 

 green. There are corresponding differences in the size and 

 juiciness of the fruit. Under the latter circumstances the lime 

 may attain to the dimensions of a considerable tree. 



The case of St. Vincent needs a special note. Although the 

 rainfall is more than sufficient and is fairly well distributed, 

 citrus trees are distinctly rare : there is not at the time of writing, 

 for example, a fruiting citrus tree of any kind, other than the 

 lime, in the Botanic Gardens or the Experiment Station. In spite 

 of many attempts at lime-growing there is not a field of bearing 

 limes in the island. Scattered lime trees may be met with and 

 oranges and grapefruit are produced in sheltered situations. 

 The form which the failure takes is that of heavy infestation with 

 scale insects and " black blight," but, as the pests found are 

 common to all the islands, these troubles can only be regarded 

 as due to the general inability of the plants to thrive. This, 

 there can be little doubt, arises primarily from the light and 

 porous nature of the soil, which, except under conditions of very 

 efficient shelter or heavy shade, does not hold a sufficiently 

 stable supply of water or contribute sufficiently to the humidity 

 of the atmosphere during spells of dry weather. The same 

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