Identification and Control Methods for Common Pests and Diseases of Bonsai

Control of Bonsai Pests and Diseases

Trunk and branch diseases:

These manifest as rot of the phloem and cambium of the trunk and branches, stem rot and cankers on the trunk and branches, surface rot of the trunk and branches, decay of the heartwood, and spots on the twigs. Usually, Bordeaux mixture should be sprayed, followed by lime sulfur mixture, and the decayed parts should be scraped off.

Leaf diseases:

Leaf diseases usually present symptoms such as yellow-brown or black spots, curled leaves, withering, and early leaf drop, and may be chlorosis, leaf spot disease, sooty mold, powdery mildew, and so on. For leaf spot disease, the diseased leaves can be picked off and Bordeaux mixture sprayed; for chlorosis, a 0.1-0.2 ferrous sulfate solution can be sprayed on the leaf surface; for powdery mildew, a 0.3-0.5 degree Baumé lime sulfur mixture can be sprayed.

Root diseases:

The roots of stump bonsai age easily and are prone to root rot or root knot disease caused by various bacteria and fungi, so attention should be paid to disinfecting the potting soil and controlling the amount of watering.

Scale insect control:

Scale insects are widespread and come in many species. They are pests that suck the sap of tree stumps, and after a tree stump is harmed by them, it is prone to sooty mold, poor growth, yellowing foliage and branches, and early leaf drop. For control, in addition to manually brushing them off and killing them, a 1000-1500 times solution of 40% dimethoate emulsifiable concentrate, or a 1000-1500 times solution of 80% dichlorvos can be sprayed to kill them.

Red spider mite control:

Red spider mites harm leaves by sucking the leaf sap, and after infestation the leaves take on a gray mottled color and are caused to wither, yellow and drop off. For control, a 1500-2000 times solution of 40% dimethoate emulsifiable concentrate or a 1000 times solution of 50% phosmet wettable powder can be sprayed to kill them.

Aphid control:

Aphids come in many species and are widespread in their damage; affected tree stumps generally have curled and drooping leaves, and in severe cases the leaf surface becomes dirty black, dry and falls off. Control method: generally a 2000-3000 times aqueous solution of 40% dimethoate is sprayed to kill them, once a week. Or a 2.5% 800-1200 times aqueous solution of derris is sprayed to kill them.

A Brief Discussion of Common Pests and Diseases of Redbud Bonsai and Their Control Methods - Experience Edition

Redbud (Cercis chinensis), a deciduous tree or shrub, can also be made into bonsai for viewing, and redbud is native to China. It likes light and has a certain degree of cold hardiness. It likes fertile, well-drained soil, and does not tolerate flooding. It has strong suckering ability and tolerates pruning. Its bark, fruit, wood and flowers can all be used as medicine, and its seeds are toxic. It is a symbol of family harmony and deep affection between flesh and blood. Below, the editor will introduce the common pest and disease knowledge of redbud bonsai for everyone's reference and study.

I. Diseases

1. Redbud angular leaf spot

Symptoms: It mainly occurs on the leaves. The lesions are polygonal, yellow-brown to dark red-brown, and later bear small dark brown moldy spots. In severe cases, the leaves are covered with lesions, which often join together into patches, causing the leaves to wither and drop off.

Occurrence pattern: It is a fungal disease, and the pathogens are two species, Cercospora and thick-walled Cercospora. This disease generally occurs from July to September. It usually infects the lower leaves first and gradually spreads upward. When the plant grows poorly, the disease is severe in rainy seasons, and the pathogen overwinters on diseased leaves and residues.

Control:

(1) In autumn, remove diseased fallen leaves and burn them in a centralized manner to reduce the source of infection.

(2) When the disease occurs, spray a 700-1000 times solution of 50% carbendazim wettable powder, or an 800-1000 times solution of 70% mancozeb wettable powder, or a 500 times solution of 80% zineb. Spraying once every 10 days for 3 to 4 consecutive times has a good control effect.

2. Redbud wilt disease

Symptoms: The leaves mostly begin to turn yellow and drop from the tips of diseased branches. Usually, individual branches are affected first, and later it gradually develops until the whole clump dies. Peeling back the bark, yellow-brown longitudinal streaks can be seen in the xylem, and yellow-brown concentric-ringed necrotic spots can be seen on the cross-section.

Occurrence pattern: This disease invades the plant roots through underground wounds, destroys the plant's vascular bundle tissue, and causes the plant to wilt and die. This disease is caused by infection by Fusarium fungi. The pathogen can overwinter in the soil or on diseased plant residues and survives for a long time. It is mainly spread through soil, underground pests, and irrigation water. It is generally more severe from June to July.

Control:

(1) Strengthen maintenance and management, enhance tree vigor, and improve the plant's disease resistance.

(2) Pay attention to crop rotation, avoid continuous cropping, or apply 3 to 5 jin per mu of 70% quintozene powder in furrows before sowing. Promptly prune out dead diseased branches and diseased plants, burn them in a centralized manner, and disinfect with 70% quintozene or 3% ferrous sulfate.

(3) A 200 times solution of 50% thiram wettable powder or a 400 times solution of 50% carbendazim wettable powder, or a 100 ppm solution of 120 agricultural antibiotic (mycotoxin) water agent can be used to drench the roots.

3. Redbud leaf blight

Symptoms: It mainly harms the leaves; the initial lesions are red-brown and round, mostly on the leaf margins, joining together and expanding into irregular large spots, until most or the entire leaf dies in a red-brown color. In the later stage, small black dots are produced on the diseased parts.

Occurrence pattern: It is a fungal disease, and the pathogen overwinters on diseased leaves as mycelium or pycnidia. When plants are too dense, this disease is prone to occur. It generally begins to occur in June.

Control:

(1) In autumn, remove fallen diseased leaves and burn them in a centralized manner.

(2) After leaf expansion, spray a 800-1000 times solution of 50% carbendazim, or a 500-1000 times solution of 50% thiophanate-methyl, once every 10 to 15 days, for 2 to 3 consecutive times.

II. Pests

1. Large bagworm

Control:

(1) In autumn and winter, remove the overwintering larval bags from the branches.

(2) From late June to July, spray 800-1200 times trichlorfon in the early stage of larval hatching and damage.

(3) Protect natural enemies such as parasitic wasps and parasitic flies.

2. Brown-edged green slug moth

Control:

(1) In autumn and winter, in combination with watering the freezing water, dig out and kill the overwintering cocoons in the shallow soil layer around the plants.

(2) When only a small amount occurs, promptly prune off the infested leaves.

(3) In the early stage of larval occurrence, spray insecticides such as dichlorvos, trichlorfon, and fenitrothion at 1000 times to kill them.

3. Aphids

Control: Spray 40% dimethoate emulsifiable concentrate at 1000 times to kill them.

It is said that redbud bonsai can not only be used for viewing but also has certain medicinal value. Its bark can be used as medicine, and has the effects of clearing heat and detoxifying, promoting blood circulation and moving qi, and reducing swelling and relieving pain. It can treat postpartum blood and qi pain, sores and swellings, and throat obstruction; the flowers can treat rheumatic muscle and bone pain, and so on.

Summary: The above is an introduction to the pest and disease knowledge of redbud bonsai, and I hope it is helpful to friends who grow redbud.

Common Pests and Diseases of Redbud Bonsai and Their Control