THE AGRONOMIST ANSWERS ON HOW TO GROW AND CARE FOR PLANTS
MY LEMON IS SERIOUSLY SICK
QUESTION FROM FRANCIS
I am writing to you again to submit a problem, I think serious, to the lemon tree that I have in the garden: Please view the photographs in order to have an idea of its condition and how I can intervene to save it. Thank you for your kindness
So Francesco, I saw the photos and on the one hand they worried me a lot but I have to understand what it is, not being able to personally view the plant ..
How long have these symptoms been showing? Can you explain to me exactly the alterations you see on the plant? What rootstock is your lemon grafted onto?
From the photos you sent me we could be faced with two possibilities, both serious:
1) gummy or root rot caused by a fungus, the Phytophthora spp.
I describe the symptoms you need to check. Keep in mind that the symptomatology I am describing is for a plant where the attack is evident and affects all its parts. It may be that in your case, the attack is just beginning and some parts have not yet been affected by the pathogen.
This disease occurs mainly in plants that have not been grafted on resistant rootstocks such as bitter orange.The disease appears mainly in the collar area of the plant with the emission of abundant gum from the bark. The bark consequently darkens and necrotizes and appears depressed and with cracks. The underground part is subject to rot. Under the bark the wood is brown. The roots crack.
The infected parts of the lemon can affect the entire crown and part of the stem
As for the aerial part, the leaves turn yellow at the level of the veins, wither and then wither and fall. The branches dry up after a while.
The fruits are less numerous and smaller in size, moreover they give off a characteristic rancid odor, then rot and then a whitish felt appears on their surface.
2) psorosis caused by viruses
Symptoms are not specific as different strains of the same virus can attack the plant. However, all lepsoroses show the appearance of chlorotic notches in the younger leaves, generally between the veins which disappear when the tissues become adults. In some cases the leaves have pale yellow variegations associated with blistering of the leaves.
The trunk and the thickest branches show desiccation followed by peeling of the bark and sometimes there is also the production of gum. In some cases the virosis causes concavities due to a different speed of growth between the parts and the diseased ones. In these concavities there is a large amount of rubber.
Both diseases are very serious but it is necessary to understand exactly what it is because while in the first case you can try to intervene and try to save the plant, in the second case, there is no cure.
I don't know where you live but if there is a Faculty of Agriculture in your area, go to the Department that deals with Plant Pathology and ask if someone can come and see your plant, they usually do, especially for these pathologies.
Let me know.
Dr. M. G. Davoli
Thank you very much for your reply; from the symptoms that you describe to me and from the fact that the lemon is grafted onto bitter orange, I believe that it may be rubbery, among other things, between the two diseases that you have proposed to me, it is the only one against which one could intervene. , as per the photographs sent, are the following: production of rubber especially in the lower part of the stem (the same rubber was also produced on a branch, along the side that looks downwards, which, in a few weeks a yellowing of the leaves, before they dried I cut the branch), cracks in the conteccia and darkening below, I have not had the opportunity to see the roots, the symptoms have manifested since last year. If it is gummy, what interventions can I do to save the plant? I will also follow your advice by contacting some agronomist specialized in the field of phytopathology; I will keep it updated.
I have carefully thought and reviewed your photos and you know what puzzles me? The blistering of the leaves which is not a typical symptom of gummy but of virosis unless you have mites feasting on your plant that show this symptomatology. In any case, show the plant to an agronomist to be sure of the disease.
I don't know if there are other citrus plants in your garden, if so, be careful, because the Phytophthora it spreads easily and in advance you must also treat the other plants immediately, carefully evaluating whether it is appropriate to risk the disease spreading to other citrus fruits or if it is necessary to take a drastic decision.
The chemical fight against gummy is generally carried out at the onset of symptoms but it can also be groped in a slightly more advanced phase. Proceed as follows: bare the collar and the affected parts by eliminating the infected bark then protect the wounds with localized treatments based on neutral cupric salts or with systemic products such as Propamocarb, Ethylphosphite of aluminum. You can also distribute these products to the surrounding land with irrigation. The ethylphisfite of aluminum also sprinkles it on the foliage (very active both in ascending and descending directions).
As a reminder, keep in mind that the treatment with systemic products works only when the plant is obviously not in vegetative rest as in this case they would move with difficulty.
On the fruits, even if in your case I do not see attacks from the photos, in general specific treatments are not carried out, however autumn-winter treatments with products based on copper salts or aluminum ethylphosphite carry out a certain action of protection.
This is all you can do but keep in mind that normally when the infection is very extensive, it is difficult to cure it completely. You would have had a few more chances if you had noticed the disease immediately and had intervened in time.
The fight against Phytophthora is above all preventive so for the future, you must make sure that there are no water stagnations by favoring the drainage of water in all ways and if possible, avoid irrigation by sprinkling. Try to avoid splashing water which favors the spread of pathogens.
In any case, let's be optimistic. Keep me informed.
Dr. M. Davoli