|Sam is oozing from the limbs of this kumquat.It sounds crazy but disease stress from management issues can cause sap oozing like this to appear. The KISS rule tells me to look at the soil and watering issues first.|
A. I usually follow the KISS rules for diagnosing plant problems. Unless we are in a citrus production area, or there is a history of disease on these trees, I first conclude it's a man-made problem. Regardless, we must rule out the simplest reasons first before we jump to more exotic disease problems.
Root death because soils are kept too wet cause these symptoms on citrus. For this reason, I assume the trees watered too often or there is a water drainage problem in the soil surrounding the roots.
Simple test if watering too often issues
After the first year of growth, all fruit trees, including citrus, should be rooted firmly in the soil. A simple diagnostic tool helps judge whether wet soils should be a concern or not. Move the tree by its trunk, back and forth, while looking at where the tree enters the soil. The tree should be firmly anchored in the soil and not move it. If tree roots move the soil easily, then the soil has probably been kept too wet and the roots began “drowning” or rotting.
There is a tendency during hot weather to water fruit trees more often, even daily. Most fruit trees, including citrus, prefer at least one day of no watering between watering days. Unless the tree is newly planted, or planted in sand, never water trees daily. Instead, increase the minutes on the clock when you do water.
Mulch can add one extra day between irrigations
Anything that shades the surface of the soil during summer helps tree roots function better. Their primary functions regarding tree health are the uptake of minerals and water. They do this better, however, if the surface of the soil is mulched. Woodchips (or even shredded cardboard, shredded newspaper or straw) lying on the soil surface gives fruit trees one extra day between waterings during the summer.
If the soil is not mulched or covered, soils dry quickly and get hot in our summer sun and heat. When soils are wet, tree roots grow where there is a good mix of air and water. Unless the soil has been amended quite a distance from the tree at the time of planting, most of the tiny roots that feed on water and nutrients grow in the top 6 inches of soil.