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Bonsai Plant Bugs
Bonsai Plant Bugs. Whatever shrub or tree species is chosen for bonsai cultivation, it's critical to start with a strong, healthy plant and tend it well. Provide the best environment possible. The less stress the bonsai undergoes, the better chance it has of surviving. Pest infestations and serious disease can badly damage a bonsai, causing loss of...
Whatever shrub or tree species is chosen for bonsai cultivation, it's critical to start with a strong, healthy plant and tend it well. Provide the best environment possible. The less stress the bonsai undergoes, the better chance it has of surviving.
Pest infestations and serious disease can badly damage a bonsai, causing loss of foliage, die-back or death. Regularly inspect your bonsai. Watch for foliage loss, damaged leaves and visible pests.
Identifying the problem & treatments
Many bugs and diseases are deadly to bonsai. Be proactive in identifying trouble early on and use the appropriate treatment to protect your bonsai.
Chemical and organic treatment options are available, and both are effective. Frequent spraying with systemic fungicides and insecticides, which are absorbed into the plant, can help. The downside of this approach is that it's not foolproof, and such sprays are expensive and environmentally unsound.
Aphids
Aphids such as greenfly and black fly suck a tree's sap. They leave behind a sticky, sugary substance, attracting ants and triggering mold. In large numbers, they can kill off new growth. Aphids can also carry viruses.
If the number of aphids or eggs is small, simply rub them off. For larger infestations, spray with soapy water or a systemic insecticide. You can press "plant pins" into the soil around the bonsai instead of spraying. The roots absorb the solution.
Lace-wing larvae can be sprinkled on the bonsai midway into spring. Each larva can consume 300 aphids.
Caterpillars
Caterpillars are quite destructive, eating holes in leaves or stripping them off. Check your bonsai closely; these blend well with foliage. Folded leaves can indicate young caterpillars hiding from predators.
Use either a systemic or contact insecticide, especially with repeated problems.
You can also remove the caterpillars by hand or use Di-Pel, an organic spray that does not leave a harmful residue.
Fungus gnats
Fungus gnats are drawn to soil that is too wet or holds moss. These tiny flies appear around indoor bonsai trees. They are especially dangerous in grub form, when they feed on the root system.
Use a household fly spray or insecticide to eradicate gnats. Take steps to improve the soil drainage so the soil is not continuously wet.
Scale insects & spidermites
These are sap-sucking bugs that attach to the bonsai.
Scale insects cause wilting, yellowed leaves and have brown shells visible on the trunk, leaves and bark. These are best removed by hand. You can try systemic insecticides, although they may be less effective because of the protective shell. In small outbreaks, paint the shells with alcohol.
Red spider mites appear in hot and dry conditions. Hard to see, these mites leave a fine webbing in bonsai leaves. Foliage will also turn yellow, then brown and die off. Treat with systemic insecticide or use a solution of organic soft soap, spraying the leaves' undersides.
Slugs & snails
Serious defoliation can indicate the presence of slugs and snails, especially prevalent during humid, warm evenings. They also leave telltale slime trails on foliage. These can generally be plucked off by hand or eradicated by pellet or liquid solution slug bait.
Vine weevils
Prevention is your best bet when combating vine weevils. Their larvae hatch in summer, then eat and destroy bonsai root systems, often causing the plant's death. If you detect wilting leaves, it's already a serious problem.
Vine weevils can leave notches in the middle and edges of leaves. In adult form, they are up to 10 mm long and black with yellow markings. Look for them on leaves' undersides.
Shake adult vine weevils off foliage. Try drenching the soil with "Bio Provado Vine Weevil Killer" insecticide. One organic approach is rubbing barrier glue on bonsai bench legs so the weevils cannot reach your plant. Or in late spring or early fall, apply heterohabditis nematodes.
