Without the pests, the ants too should disappear.
} Yellow Leaves Due to Lack of Nitrogen. If your lemon tree shows chlorosis of the leaves, that is, yellowing due to lack of chlorophyll and this affects the older branches first and spreads to the younger ones, this is a case of chlorosis due to lack of nitrogen.
Nitrogen, or N, is one of the main nutrients for lemon trees. Without it, they cannot grow or develop properly and it is an. Jun 12, Not Enough Nitrogen. Yellow leaves are often an indicator of insufficient nitrogen. Test soil around the root base for NPK (Nitrogen, Phosphorus, and Potassium) with a simple home test kit, available online and at some hardware stores. And their symptoms can look very similar.
The tissue between leaf veins turns yellow or pale green, but the veins remain dark green, at least initially. When manganese is deficient young leaves turn light green between the veins. Lack of zinc is seen as small terminal leaves with yellow mottling between the large veins.
Iron deficiency is suspected if leaves are yellow while veins remain green. Foliar sprays. Aug 06, Apply a solution of % saltpeter about a month to 6 weeks before bloom time to increase flowering. Then from bloom to mid June, do not let the tree get too dry. This is a balancing act--too dry the tree will drop fruit, too wet the tree can develop root rot (If you have a good chunky soil with lots of air that will not happen). Citrus trees.