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Pest and Disease Control Methods and Technical Key Points for Bonsai

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Diseases on branches and trunks: These manifest as rot of the phloem and cambium of branches and trunks, stem rot and cankers on branches and trunks, surface rot of branches and trunks, decay of the inner wood, and spots on twigs. In such cases, Bordeaux mixture should usually be sprayed, followed by lime sulfur mixture, and the decayed parts should be scraped off. Foliar diseases: Foliar diseases usually show symptoms such as yellow-brown or black spots, leaf curling, wilting, and early leaf drop, and may be chlorosis, leaf spot disease, sooty mold, powdery mildew, etc. For leaf spot disease, remove the diseased leaves and spray Bordeaux mixture; for chlorosis, use 0.1-0

Diseases on branches and trunks: These manifest as rot of the phloem and cambium of branches and trunks, stem rot and cankers on branches and trunks, surface rot of branches and trunks, decay of the inner wood, and spots on twigs. In such cases, Bordeaux mixture should usually be sprayed, followed by lime sulfur mixture, and the decayed parts should be scraped off.

Foliar diseases: Foliar diseases usually show symptoms such as yellow-brown or black spots, leaf curling, wilting, and early leaf drop, and may be chlorosis, leaf spot disease, sooty mold, powdery mildew, etc. For leaf spot disease, remove the diseased leaves and spray Bordeaux mixture; for chlorosis, spray the leaf surface with a 0.1-0.2 ferrous sulfate solution; for powdery mildew, spray with a 0.3-0.5 degree Beaume lime sulfur mixture.

Root diseases: As bonsai roots age, they are prone to root rot or root nodule 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 bonsai trees. After being damaged by them, bonsai trees are prone to sooty mold, showing poor growth, yellowing and withering of branches and leaves, 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 leaf sap. After infestation, the leaves take on a gray spotted color and then turn yellow, wither, and drop off. For control, spray with a 1500-2000 times solution of 40% dimethoate emulsifiable concentrate or a 1000 times solution of 50% isocarbophos wettable powder.

Aphid control: Aphids come in many species and are widespread. Affected bonsai trees generally have curled and drooping leaves, and in severe cases the leaf surface becomes dirty black, dries up, and drops off. Control method: generally spray with a 2000-3000 times aqueous solution of 40% dimethoate, once a week. Or spray with a 800-1200 times aqueous solution of 2.5% derris.

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