What are the common pests and diseases of magnolia, and how to prevent and control them?
Magnolia is one of China's early spring ornamental flowering trees and shrubs, with a classical and elegant flower form. It is generally planted in pavilions, terraces and towers as a decorative accent. So, what are the common pests and diseases of magnolia, and how to prevent and control them?
1. Leaf spot disease: At the beginning of the disease, there are only small dark red dots on the leaf surface. If not treated in time, they will rapidly expand and merge into large patches, causing the leaves to wither and drop, seriously affecting its ornamental value. Therefore, you should regularly observe the growth of its leaves, and once disease is found, treat it promptly.
Control method: You can use a 50% thiophanate-methyl 800-fold solution for foliar spraying, once every 7-8 days, and it can be cured after 2-3 consecutive applications.
2. Scale insects: Most are mainly chaff scales. If scale insects are found, you can use imidacloprid or an imidacloprid improved formulation at 2000-3000-fold solution for spray insect control.
3. Pittosporum cottony cushion scale: It mainly harms flowering trees and shrubs, has a very wide host range, and causes widespread damage. Female adults and larvae often gather on young buds, leaves, branches and trunks to suck sap. In severe cases, they can cover entire branches, causing leaves to turn yellow, shoots to become short and deformed, leaf drop, dead branches, and even the death of the whole plant. It also easily induces sooty mold, making the leaf surface black, hindering photosynthesis, affecting tree vigor, and thereby reducing ornamental value. When first- and second-instar nymphs feed on sap, they secrete large amounts of honeydew, which is the main cause of sooty mold. After female adults mature, they often remain fixed and cause damage, no longer moving.
Control methods:
(1) Silvicultural measures: Remove pest-infested plants in the field and prune insect-infested branches, and promptly carry them out of the field for burning.
(2) Biological control: Protect and introduce the Australian ladybird beetle, and the large and small red ladybird beetles.
(3) Control: During the dormant period, spray with 1-3 degrees Baumé lime sulfur mixture; during the nymph hatching period, you can use 40% omethoate emulsifiable concentrate 1000-fold plus 10% imidacloprid wettable powder 1500-fold solution; when adults occur, use Kuangshajie 800-1000-fold solution or 40% Supusha emulsifiable concentrate 1500-fold solution for uniform spraying. Adding an appropriate amount of diesel oil when spraying can increase its permeability, and the spray solution must be sprayed thoroughly and evenly. Kuangshajie is effective against scale insects.