THE AGRONOMIST ANSWERS ON HOW TO GROW AND CARE FOR PLANTS
BURGUNDY STAINS ON ALMOST ALL THE LEAVES OF MY PHOTINIA
QUESTION FROM RICCARDO
Hello and congratulations for your site.
I wanted to bring you a problem that I encountered with my Photinia hedge. The hedge was planted in the garden in May 2008 and is exposed to full sun throughout the morning and part of the early afternoon. The only fertilization I did just after planting with pelleted manure. As for irrigation, in summer and spring I watered regularly (every other day for about 10 minutes) while in autumn and winter I didn't water at all. At the base of the hedge I placed a bed of red bark to hide the part of the ground where the grass does not grow.
As you can see from the attached photos, the problem I encounter is due to the appearance of burgundy spots on almost all of the leaves. I don't notice the presence of any insects or anything else.
I want to clarify that about 20 meters away I have another Photinia hedge that does not present any problems.
A friend advised me to proceed with a nice "sprinkle" of verdigris.
How should I behave?
what your photinia has is unfortunately evident: an attack of Entomosporium maculatum a fungus that affects photinia (and other plants belonging to the Rosaceae family), very harmful and not easy to control and cure.
The first symptoms are the spots you see, initially evident only on the upper page of the leaves and later also on the lower one. Gradually these spots increase, unite and form larger spots that become darker and in correspondence of the central part you can see blackish little bodies that are the fruiting of the fungus. As a final consequence you have the fall of the leaves. The attacks are generally localized only on the leaves but can also reach the twigs where lesions of various shapes appear, similar to those of the leaves or as small elongated cancers. It can also affect fruit although it is rare.
Now that the temperatures are rising and the climate is very humid, it is the optimal time for them, also favored by the continuous rains.
Now, I'm sorry I'm not very positive but it is a serious disease and it will take a lot of patience on your part to try and save the plants. I will give you some indications of both agronomic and phytosanitary nature, both fundamental to try to save plants.
In consideration of the fact that the vegetative restart of the plant has not yet fully begun, do a pruning and only eliminate the affected parts (I do not advise you to make it too heavy because as you know pruning stimulates the production of new branches and therefore of new leaves) being very careful that you do not miss even a leaf that you will have to take away and if you can burn them being very careful that they do not come into contact with the other group of plants. The physical elimination of leaves (including fallen ones) is fundamental for the control of the disease as fruiting bodies are formed on the leaves that contain the spores which are the organs through which the fungus spreads (which continue to develop even if the leaf detaches from the plant).
As soon as the warm season arrives, do not do any more pruning, only remove the leaves you see sick.
When watering, try not to get any part of the plant wet as the spray promotes the spread of spores. Furthermore, for safety, it would be advisable to water during the hottest hours of the day so that the environment dries up quickly (humidity is a precious ally for this fungus).
Make sure that there is good air circulation between the leaves as a dry environment limits the proliferation of the fungus.
After doing this, treat the plant with one of these products (I give you a list of some active ingredients): Daconil or Chlorothalonil or Methyl thiophanate or Propiconazole which you can find at an Agricultural Consortium. Follow the instructions on the label but on average do the treatments every 10-14 days (the longer period as the summer arrives and the climate is drier) and keep in mind that many of them are classified as harmful (for which take all the necessary precautions and be careful if you have small children or pets) and do the treatments until about the first / mid June then suspend because the dry environment is already a deterrent. For the autumn we need to see the conditions of the plant. It is early to give directions.
As a prevention, I would advise you to do the treatments also to the other group of photinia plants and to keep them under close observation. Be very careful that any tools you use for photinia malata, if you use them for other photinia plants, you must clean and disinfect them well (preferably with the flame) and the same goes for your hands (obviously not for the flame).
If you have any other rosaceae, keep them under close observation and take great care that they do not come into contact with any part of the diseased photinia.
I'm sorry I can't give you better news but I still have to point out that it is very difficult to control this disease, some recommend eliminating the plants immediately but personally I think you should at least try.
If you have any doubts, write me.
Dr. M.G. Davoli