180 H. A. BALLOU. 



as I am aware, cacao in Grenada is known to be attacked by only two scale-insects. 

 These are the common mealy bug {Pseudococcus citri) and the akee fringed scale 

 (Asterolecaniwn jnistulans). I have seen the common mealy bug present in some 

 numbers on the leaves and pods of cacao, but they do not seem to do any appreciable 

 harm, and the cacao-planter does not consider that it would be worth while to spray 

 his trees for the control of this insect. As for the other scale mentioned, it was reported 

 a few years ago as seriously attacking one tree in a peasant's cacao plot and it 

 was recommended that the tree should be destroyed. On this recent visit, 

 I found a few specimens of this insect on a cacao tree, but so few that they could 

 not be said to be doing any appreciable harm. Any planter can control these insects 

 if they tend to become seriously abundant. 



Cacao has been grown in Grenada for many years, and for the last twenty-five years, 

 perhaps, it has been the principal crop. Most, if not all, the scale-insects which occur 

 as pests in Grenada either are indigenous to that island or have been established there 

 for a long time. No new scale-insect pests seem to have made their appearance in 

 Grenada during the sixteen years that this Department has been working, and it may 

 be stated with certainty that if any of the known insects in Grenada were likely ever 

 to become pests of cacao they would have manifested that tendency before this. It 

 is known also that scale-insects do not often change their food-plant, or at least, they 

 usually have a narrow range of food-plants. There are not apparently many species 

 of trees in Grenada closely related to the cacao, from which scale-insects might spread 

 to that tree. 



In the matter of fruit trees, the situation is somewhat different. The scale-insects 

 which attack the orange, lime and other citrus trees are serious pests. In Grenada, 

 the mango trees are often thoroughly infested with black blight, and it is in connexion 

 with these trees perhaps that it is most commonly noticed. Whatever injury the 

 mangoes suffer is not, however, the result of the black covering so much as of the 

 presence and feeding of myriads of scale-insects, of which the mango shield-scale 

 (Coccus mangiferae) is the most abundant. This insect occurs on several plants other 

 than mango, such as breadfruit, nutmeg, sapodilla and cinnamon. 



When the planters learn to recognise the different scale-insects on these trees 

 sufficiently to estimate the amount of damage done by them, and when the conditions 

 of soil and exposure to wind, are considered in relation to the condition of the trees, 

 it will be possible to estimate correctly the injuries resulting from plant pests in a 

 manner not possible while the conditions are all confounded under the general term 

 black bUght. 



Control of Scale-Insects by Natural Enemies. 



Recommendations have been made from time to time with regard to the intro- 

 duction into Grenada of the natural enemies of scale-insects, principally the entomo- 

 genous fungi, as a means of controlhng black blight. It is now known that there are 

 in the island many well-established scale-insect parasites, and it is not likely that any 

 good can be accomplished by the importation of fungus parasites from other islands, 

 seeing that the known ones are all present, but a judicious distribution of them from 

 places in the island where they are abundant to others where they are not, may have 

 the effect of checking the scale-insects earher than would occur by natural spread. 



