That's not a kumquat; it's known as a loquat
Q: We have a tree that produces a neat little fruit that we have been told is a kumquat. Please tell us what it really is. Tim Gromlovits
A: The picture that you sent is that of a loquat or Japanese plum (Eriobotrya japonica) a medium-sized 20- to 30-foot evergreen, cold hardy tree, with a tasty fruit that is in the rose family as are apple and pear. Many people call it kumquat which is in the citrus family and tastes nothing like the loquat. I guess since they have the "quat" in common they regularly get confused.
Sometimes even your resistant native plants can get pests
Q: Six years ago we tore up the front lawn and planted Florida natives due to their drought and insect resistance. Lately, our marlberry (Ardisia escallonioides) and necklace pod (Sophora tomentosa) have been getting their leaves chomped by something. Every leaf on the marlberry has the edges completely notched. Upon close examination we found a few of these white and black beetles and a cluster of maybe eggs. I have sprinkled with Diple Dust a few times but can not get the insects under control. If they are beneficial insects I do not want to kill them. Mike Bandera, St. Petersburg
A: You have two different pests, mealybug on your necklace pod (Sophora tomentosa) and Sri Lanka weevil on your marlberry (Ardisia escallonioides).
Mealybug is a mobile soft scale and a common pest of necklace pod. It is best to prune off as much of the infestation as possible and then follow up with neem oil sprays on a weekly basis until control is achieved, then closely monitor so another build up doesn't occur.
Sri Lanka weevil has been an increasingly notable pest of citrus and many other fruit trees, but this is the first that I have seen on one of our natives. They won't kill your marlberry, but they sure will make salad out of the leaves. Sri Lanka weevils are lazy and don't like to fly unless really disturbed, so if control is warranted, spray Sevin, Orthene or Talstar in the morning making sure to contact the colonies of weevils. Monitor and spray as needed following label directions.