Magnolias occasionally experience dieback. To prevent this situation, here are some important causes and methods of prevention.

Note!
A highly beneficial practice in combating diseases and pests is spraying plants in the garden in autumn (October) or spring (March-April) when the temperature is above +10°C with paraffin oil. I believe that these few remarks provided below will contribute to a better understanding of magnolia requirements and help avoid many mistakes.

1/ Improper soil

Usually, it contains too much calcium. The roots of magnolias do not develop properly and begin to die off. Yellow discoloration (chlorosis) appears on the leaves. The veins remain green. With a high calcium content (pH 7.0 or higher), the youngest leaves are completely lemon-yellow and wither. The only solution is to properly prepare the soil before planting. In the case of excessively high pH, acidic peat or heather soil should be added and mixed in. For magnolias already growing in such conditions, mulching with acidic peat and using both acidic peat and a 0.1% iron chelate spray solution (10g per 10 liters of water) can be a solution. For a mature magnolia, about 50-100 g of chelate dissolved in 50-100 liters of water should be applied as a soil drench once a year.
Magnolias also grow poorly in very compacted and waterlogged soils, as well as in sandy soils. In the case of excessively light soil, a hole with a diameter of 1.5 m and a depth of 50 cm should be dug and filled with fertile, permeable soil. It should be remembered that acidity should never be higher than pH 6.0-6.5.

2/ Damage by rodents

It often happens that mice or voles gnaw on the roots of magnolias and the lower part of the trunk (below ground level). This can only be discovered after uncovering the topsoil. In the case of trunk damage, the wounds should be sealed with emulsion paint with the addition of 1% Topsin. In the event of severe damage, magnolias may produce small yellow leaves in spring, which then die off. The soil around magnolias should only be covered in late autumn, when the top layer of soil is already slightly frozen.

3/ Overfertilization of nitrogen

It promotes their vigorous growth but also increases susceptibility to frost damage. Nitrogen fertilizers should not be applied after July 15th.

4/ Excessive fertilization

Excessive fertilization can cause a growth limitation, leading to increased soil salinity. In magnolias growing in such conditions, the oldest leaves start to wither from the edges by the end of July. We can partially prevent this by watering the plants generously 2-3 times a week during the growing season to flush out excess fertilizers.

5/ Drought

Excessive drying out can cause a lot of damage to magnolias during hot spring and summer weather. Once a young magnolia has dried out, it is practically lost.
Let's make sure to water them at least once a week.

6/ Spider mites

Bardzo wiele szkód wyrządza w czasie suchej, upalnej pogody przędziorek. Jest to szkodnik atakujący wiele roślin. Żeruje na spodzie liści nakłuwając je i wysysając soki. Silnie zaatakowane magnolie gubią liście już w lipcu-sierpniu. Są one wówczas tak osłabione, że w następnym roku dają bardzo małe przyrosty.

7/ Bacterial leaf spot

It is a disease characterized by brown, round spots on the leaves. Magnolias should be sprayed in the leafless state in early spring with copper-based preparations (e.g., Copper oxychloride at a concentration of 0.3%). The treatment should be repeated in early autumn.

8/ Powdery mildew

Jest to choroba pojawiająca się w czerwcu i lipcu na liściach. Mączysty nalot deformuje blaszkę liściową i powoduje jej zamieranie. Zwalczanie tej choroby polega na usuwaniu i paleniu opadniętych liści jesienią oraz opryskiwaniu krzewów dostępnymi preparatami chemicznymi.

9/ Lack of winter covering

This is one of the fundamental cultivation errors that often results in the young root system freezing. It is advisable to cover the soil around the trunk with a thick layer of sawdust or bark, about 20-30 cm thick.