Gall wasp is something that nearly every lemon grower in the country has to deal with. In fact, very few trees are exempt. It is a microscopic native wasp that burrows its eggs into the limbs of citrus -primarily lemons and also grapefruit - which then cause swellings or ‘galls’ on the plant, from which the insect hatches.
It’s easy to tell if the wasp has emerged because you will see tiny holes – like a prick from a needle – signifying their departure. Galls without holes means the culprits are still hiding out in the limbs of your plant.
Although gall wasp will not completely kill a tree, it will greatly reduce its health, and more importantly, productivity, when left to spiral out of control.