Bonsai Pest Problems

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Totally Bonsai A guide to growing , shaping and caring for miniature trees and shrubs

Craig Coussins

Pest Problems and Solutions

Problem Cause InsecticideTreatmentOther Information
Sticky leavesAphids.

Greenfly are the most common.


Black fly can land in the evening and devastate a tree within 48 hours. They hide under the leaves, too, and are like black dots with legs.

Systematic and foliar.

Aphids can be removed by hand but treat for future attacks.
Read Pack.

Foliar: Once every 7 days under and on top of the leaves.

Systematic: In soil every 2 weeks.
A new systematic currently available is Provado, it is excellent for soft- leaved trees such as maples.
you can also treat with lime sulfur:2- 4 drops per print ( half- liter).
Sticky leaves and small white insects under leaves.Whitefly.Systematic and foliar.Read pack.


Foliar: Once every 7 days under and on top of the leaves.

Systematic: In soil every 2 weeks.
Wash off all traces with a spray or a hose. Treat under the leaves, too.
White leaves and small white insects under leaves.AdelgidsSystematic and foliar.Read pack.


Foliar: Once every 7 days under and on top of the leaves.

Systematic: In soil every 2 weeks.
Wash off all traces with a spray or a hose. Treat under the leaves, too.
you can also treat with lime sulfur:2- 4 drops per print ( half- liter).
Lack of vigor, leaves not growing properlyVine weevil.
Becoming a real problem in many countries.
There are specific treatments for this including Siskin Green and now Provado.Check soil for grubs at re-potting time. Read pack.

Systematic: In soil according to instructions
A new systematic currently available is Provado. Used against vine weevil, it is excellent for soft- leaved trees such as maples.
yellow stripes on pine needles.Pine- needle cast
(Lophodermum pinastre).


This is a fungal disease.
Copper sulfur.Read Pack.

Foliar: Once every 7 days under and on top of the leaves.
Repeat every 7 days for at least 3 weeks to stop the fungal growth cycle.
It is important that the copper does not enter the soil level, as it will damage the beneficial mycelium in the roots.
Protect with a cloth and plastic bag or sheeting over the soil.
After winter damage on pines, weak growth on all trees.Cold drafts, shaded too much, lack of watering . Lack of vigor in leaves can also mean the tree is not getting enough trace elements.Top dressing with amino and nucleic acids, trace elements, and organic nutrients.Top Dressing GK365 is a new product from Japan and many masters are impressed by it.
This growth, no vigor.Insect attack in soil. Root aphid, leather jackets, etc.Soil insecticide, systematic insecticide.Read pack.

Once every 7 days.
Be careful you do not treat trees that do not take to a root- drench.
Read pack.
Gray areas on leaves, small wet webs between leaves.Botrytis/ mildew.

This is a fungal mold caused by turgid air and damp conditions. Affects anything but especially cuttings and young seedlings.
fungicide, but be careful not to get it into soil.There are brand- named treatments for botrytis or mildew so check with your bonsai nursery.If this is happening change your air flow and get fresh moving air to your bonsai.
Gray- looking foliage on junipers and needle junipers.Red spider mite. to check if this is in residence , put your hand under a branch and shake the branch. Tiny mites will drop onto your hand.systematic every 7 days until clear. Usually 5 weeks.Read instructions.A more common cause for concern that people realize. If you get Red Spider Mite then check all your needle foliage trees. If it is on one it’s probably on the lot.
Holes in leaves.Caterpillar attack, leaf- cutting bees, insects that like to chomp leaves!First, check the underside of foliage and look for insects hiding. look around the root area as well. Lift moss.
Immediate foliar spray, followed by systematic.
Read instructions.It is precisely why you need to spend at least 15 minutes a day checking your bonsai to reduce insect attack.
work growth with brown or gray on the branches and trunk.sapsuckers, scale insects.These require a little more work. dip a cotton swab top in a little rubbing alcohol and rub off each one . Followed by a systematic soil drench and foliar spray.Read instructions.check every spring and midsummer and especially before any winter dormant.

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