Q. Something is eating the leaves of my small grapefruit tree. I have checked it often to see if I could see the pest that was the culprit, even at night, and cannot find anything. What do you recommend?
A. Without seeing it I am not sure anything is eating your grapefruit leaves. Wind damage to the leaves is the most common reason for damage to citrus leaves that resembles feeding damage by insects. We did have some pretty good winds recently. Wind damage most resembles tearing, shredding or ripping of leaves. I would not apply an insecticide if you are not convinced it is insect damage and then only if the damage is not recoverable by the tree without your assistance or interferes with fruit production.
Wind damage to persimmon leaves.
I don't think that was wind damage. Looks like pesticide drift. The plant shows chemical damage, that causes the leaves to be brittle, new growth is small and deformed. I see that everywhere nowadays :((((
The only reason I know that some of that damage is due to the wind is because of the high winds just before I took that picture. You might be right. The damage could be compounded because of weed killer damage. But the damage and loss to the leaves, not the distortion, is what I'm talking about.