Growing bonsai? Knowing about plant pests comes with the territory!
Because we use many different kinds of plants to create bonsai trees, there are many different problems to watch for. Any site about bonsai plant care is not complete without this discussion.
The biggest problem is: not all of them are susceptible to the same diseases and insects.
Juniper bonsai trees - such as this cascade by Ed Trout are susceptible to red spider mites.
If you don’t know what’s crawling on your tree, or why your tree is doing something weird (like wilting or dropping leaves), always ask! Each time you venture to another species, research the potential plant pests and diseases for that plant.
Remember, just as there are good reasons for some plants to wilt or drop leaves. There are also many more good bugs
than bad. If you don't know, never spray pesticides first.
We often assume mites only attack our juniper bonsai, not so! I have seen them on everything from regular house plants to trees in the yard.
Their feeding causes the plant to appear off-color and eventually turn completely brown. Another symptom is the webs they weave (where they lay eggs).
Mites can kill plants quickly. When you have a bonsai that has a gray caste to it or one that just doesn’t look quite right, suspect spider mites!There are many pesticides to use – organic and chemical. One good choice is the Safer Brand Insect Killing Soap, Ready to Use Spray
Mealybugs are soft-bodied insects that are often covered with cottony white filaments. You may be surprised at how many different kinds there are.
In this enlarged photo they are shown on asparagus fern. They are especially fond of foliage plants and will often show up on bonsai Ficus varieties. (Especially indoors.)
The mealybug is something you want to catch early, they are one of the causes of black sooty mold!
Another terrible invasion of plant pests can come from root mealy bugs! They are worse than the above ground kind, and very difficult to see!
(The soft bodied mealybugs (shown above) are also considered a type of scale. Often spraying a contact pesticide is not enough. Horticulture oils and systemics work best. )
Borers nearly always attack unhealthy or stressed plants or trees. Although you may think your tree is healthy, what about the injuries from cutting? These 'wounds' are perfect entry places for borers.
Not as common as many other plant pests; borers are something to always be aware of. Some bore deeply into the wood however, many bore just under the bark.
Keep your eyes open for "frass."
Frass is excrement from what larvae have eaten. When they are eating woody plants, the refuse left behind is much like sawdust. If you see any sawdust on the soil, draw a visual line straight up to the trunk or branch above. Look for a tiny hole, although sometimes they are barely visible. When you see these signs, find the soft area.
Try to gouge out the area as soon as possible. Don't stop digging around soft spots until you find something. A beetle and/or larvae are almost always still there! You may end up with a terrific shari or as in the ugly damage shown here, you may not be so lucky!
Nashia inaguensis is one of the few species Pit Scale is particularly attracted to. See a full description on that page.
Guest Author Lee Squires wrote an article on how he lost many of his bonsai to an: Invasion of the Voles!
Ready for some good news? There are more plant "beneficials" than plant pests. Some you may not recognize and others you may have wrongly decided are bad, could be beneficial bonsai care helpers!
Pests are not the only problem when growing bonsai, go to Bonsai Care
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