So I went to water my potted grapefruit tree yesterday and I saw loads of tiny flies around the base of my tree and some walking up and down the trunk. They were crawling all over the bark mulch covering the mix.
To provide a little context: I repotted this tree into 5-1-1 mix in the peak of summer and it never really recovered. It stopped getting worse, but never really got happy. I assumed it was it was just too hot for the roots to re-establish themselves in the new mix.
Anyway, fast forward to yesterday and I see all the tiny flies. I know pests are primarily a problem when a tree is stressed. I did not recognize these insects on any "citrus pests" documents, I don't know what they are. They almost looked like gnats except these were a tad bigger and some looked like they were carrying something white. This tree is kept outdoors and these did not look like whiteflies or mites (according to pics).
Any suggestions about what to do? Temps right now are low 40s overnight and daytime highs of about 70. The pervasiveness of the bugs on the mulch makes me wonder if a repot is necessary. Or, is this something a horticultural oil or neem oil could help with? I've not spotted explicit signs of damage to leaf or limb, just a failure to thrive.
I should add that Meyer lemon and peach trees in same mix and watering schedule do not show signs of infestation or stress.