Magnolia grandiflora is a tree species with strong disease resistance, and its main diseases are anthracnose, yellowing and leaf burning.
Symptoms and laws of etiological diseases: first, the leaflets fade, chlorophyll gradually decreases, the leaves are yellow or light yellow, and the veins are still green. After the disease expands, the whole leaves turn yellow, then gradually turn white, and the plant growth gradually declines and eventually dies.
Prevention and control methods: Yellowing disease is a physiological disease, which is mainly caused by excessive soil viscosity, high pH value and insufficient iron supply. Roots can be irrigated with 0.2% ferrous sulfate solution, leaves can also be sprayed with 0. 1% ferrous sulfate solution, and more farmyard manure can be applied.
Mulan disease: anthracnose
symptom
The leaves of Magnolia grandiflora are most susceptible to this disease.
In the early stage, irregular lesions will appear at the tip or edge of the blade, or approximate circular lesions will appear on the blade surface. At first, the lesion was brown, with water stains, small black particles on the surface and raised dark brown thin lines on the edge, which was obviously different from normal parts.
The hot and humid weather makes summer the peak of this disease. If the amount of water and fertilizer is not properly controlled and the ventilation work is not done well, plants are easily infected with this disease.
Prevention and cure method
Grasp the amount of water and fertilizer, let plants grow healthily and enhance their disease resistance.
Ill leaves should be removed in time, and fallen leaves in late autumn should be swept away in time.
If you get sick, you can spray 800 times of 75% chlorothalonil wettable powder or 500 times of 70% anthrax thiram (once every 10 day) for 3-4 times, which can effectively control the deterioration of the disease.
Mulan disease: yellowing disease
symptom
The initial symptom is the decrease of chlorophyll in leaves, which leads to the green of lobules. Gradually, other leaves will turn yellow or light yellow, but the veins are still green.
The further deepening of the disease will make all the leaves turn yellow and then white, which will lead to the continuous decline of plant growth and eventually death.
Prevention and cure method
Yellowing is a physiological disease, which can be caused by too high soil viscosity, too high pH value and insufficient iron supply.
Irrigation with 0.2% ferrous sulfate solution or spraying with 0. 1% ferrous sulfate solution can effectively control the disease, and more special fertilizer for Lamla should be applied.
Mulan disease: leaf burning
symptom
At first, the disease showed that the leaves of plants were burnt, and the leaves would gradually shrink and dry up. When the disease gets worse, the new leaves will be difficult to stretch, and finally a large number of leaves will die and fall off.
The disease will occur in places with poor geological environment such as large hardened area and small green area, and will be affected by high temperature, drought and strong light for a long time, and the soil will be alkalized.
Prevention and cure method
First of all, increase the amount of water to ensure the soil is moist.
Apply organic fertilizer regularly to enhance the disease resistance of plants.
You can also take measures to paint the tree white or contract it.
Pest of Mulan: Ceroplastes rubra
Symptomatic manifestation
The nymph and adult of Ceroplastes rubra suck flower juice, and its excrement often induces sooty blotch, which makes the leaves form a layer of black mold or a thick black film, and the whole plant becomes a black tree, which is weak and rarely or completely unable to bloom.
Prevention and cure method
In winter and early spring, pruning is combined to eliminate some insect-infested branches.
If the damaged flowers are few or short, you can scrape them by hand in winter and spring.
At the peak of nymph incubation, spray 25% phoxim EC 1000 times or 40% omethoate EC 1500 times, spray 1 times every 4 ~ 6 days, and spray for 3 times continuously.
Magnolia pest: red spider
Symptomatic manifestation
Red spider mainly harms leaves and feeds on leaf juice. At the onset, reddish-brown spots will appear on the leaves. In severe cases, leaves will wither and branches will rot.
Prevention and cure method
Soak the orange peel with water of 10 times for one day and night, filter and spray the plants.
Washing powder 15g, 20% caustic soda 15ml, 7.5kg of water, and then spraying plants.
Plant ash 50g, soaked in 2.5kg water for two days and nights, filtered, mixed with 3g washing powder and sprayed, once a day, three times in a row, and three times a week. When put into the soil, the second generation pests can be eliminated and maggots can be prevented.
Light the mosquito-repellent incense 1 tray, put it into the diseased plant basin, and then tie it tightly with a plastic bag. After 1 hour, eggs and adults can be killed.
Magnolia pests: fried cicadas
Symptomatic manifestation
The nymphs who fry cicadas suck the root juice of the flowers in the soil, the adults suck the juice of the main leaves, and the females insert the ovipositor in the branches to lay eggs, resulting in the branches dying.
Prevention and cure method
Kill the newly unearthed mature nymph in time.
If it is serious, you can make a fire near the trunk and shake the branches on a hot night in summer, so that the cicada will be killed by the fire and kill the cicada that falls outside the fire.
Sticky dough kneaded with cooked tung oil or cobwebs is coated on the end of bamboo poles to catch adults.
Check and cut off spawning branches in time from April to August.