CHAPTER V.
DISEASES.
The olive tree is so robust by nature, and its bark, leaves and fruit are so bitter that in consequence of those diflferent advantages it is less exposed than other trees to the ravages of insects and animals, especially when it is planted on hills and mountains, on light and well drained soils, for, no one can ignore the fact that fruit trees in general are so much more exposed to the many pests that endanger their existence and check their bearing capacity as they are planted in low and moist lands.
The most dangerous enemy of the olive tree seems to be the black scale. This insect has a marked preference for the orange tree, as well as for the laurel tree, which are generally planted in rich soil and very seldom on high elevations or meagre and well drained lands.
Under the shape of very small shells of a dark brown color, these insects fasten themselves very closely to the branches, leaving after them a trail of a blackish dust formed by the sap they extract from the tree mixed to their leavings, the whole
