Consider purchasing nematode-resistant plants to avoid the problem. Some varieties of plants are resistant to nematodes and many woody plants are grafted on resistant wood stock. In you are preparing new ground for planting and want to insure a nematode free area, solar sterilization of the garden plot over the summer is another possibility. Cover the garden tightly with clear plastic for two and a half months from the middle of June to the end of August. The only way to keep birds off your citrus would be to invest in bird netting.
Netting is used up north for cherry trees and blueberry plants.
Park's Seed and other major mail order houses carry the netting. You might also try hanging a replica of an owl. That seems to discourage many birds. However, you need to move it occasionally or the birds get wise and return when they realize the owl isn't real. I've also seen strips of foil or shiny aluminum pie plates attached to the branches with bits with string, thereby allowing them to flutter in the breeze, used as an avian deterrent.