Lemon tree problem.
We have a young lemon tree, two years old, the leaves near the top of the tree are constantly bombarded by insect eggs that kill the leaves and turns the stalk black, these are quickly replaced by new leaves from suckers sprouting from the bottom. I have washed off the infected leaves individually and tried to clean off the black deposits but they still die off. This means that the tree does not increase in size but is constantly renewing itself from the bottom. I have tried the usual citrous tree suplements but with no effect, I have sprayed with insecticide but this offers very short term relief, the secret appears to be to eradicate the bugs but with what?
Any advice would be welcome.