The Q&A Archives: Sick Eureka Lemon Tree

Question: In March, I purchased a Eureka Lemon tree (for a container indoor/outdoor plant, which I acclimated and is now in a sunny location on my patio). It has been dropping leaves to the point where now only a few remain, and there is no new growth. Also, on the trunk, near the soil-line, there is a small amount of sap oozing from the bark. I have tried a citrus tree fertilizer, also a pesticide recommended by the nursery, but so far nothing seems to be working. Do you have any ideas about what could be wrong? Also, I'm not quite sure what to do about the sap.
Any information you could provide me would be greatly appreciated.
Elizabeth Neuman


Oozing sap usually indicates a wound - either from insect activity, disease, or even mechanical injury. A healthy tree will eventually compartmentalize the damaged tissues and heal the wound. You don't need to remove the sap or try to stop the flow - the tree will stop the flow eventually. As for the yellowing leaves, several things could be wrong. When young leaves (those near the end of shoots) turn yellow, we ususally consider an iron deficiency to be the cause. High pH, high phosphorous and of course low soil iron levels all can result in iron deficiency symptoms. If older leaves are yellowing, nitrogen may be deficient. However, with iron or nitrogen deficiency, the leaves usually do not fall from the plant.

Root problems are a more likely cause. Root rot infection, physical damage to roots, drought and overwatering (soggy, waterlogged soil) can all cause leaves to turn yellow and fall.

Try to determine which of the cultural problems listed above may be the cause and take steps to alleviate it. If a root rot disease is present, there may be little that you can do at this time other than to avoid overwatering which tends to make things worse.

Another possible culprit is Citrus Mesophyll Collapse. Grapefruits are particularly susceptible but any citrus may be affected. It is not uncommon for grapefruit trees to be affected and other nearby citrus to be fine. Leaves and fruit of citrus trees dry up and drop. Stems and branches remain green and living. Rarely is the whole tree affected. Mesophyll collapse occurs when there are unseasonable weather changes. For example if it gets abnormally cold in October for several days and then heats back up above average temperature in November. This fluctuation stresses the trees as they kick into and out of and then back into their winter slow down. It is especially stressful after a dry summer.

Remove fallen leaves (and fruit) to prevent attracting fungal and bacterial diseases. Continue to water the tree on its normal cycle and it will leaf-out again as soon as it's able. Do not prune out the defoliated branches until new growth begins and you're sure the branches are dead.

Good luck with your citrus tree!

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