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, Ft. Lauderdale, FL -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.
If that sounds scary, read more
about Aphids here.
The type of mites we see most often are what we call red spider mites. They are barely visible, but can be easily spotted on a piece of white paper.
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!
Greatly enlarged mite illustration by Eduardo Varona.
Mealybugs - are a well known common pest. (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!
Root mealy bugs are often misidentified! Be sure to read about them.
Scale - Scale is a sucking insect. It has many appearances but It often appears as a light brown bump or white spot on a leaf or stem. Many scale insects have a waxy covering. Some even look like small oyster shells. They remain immobile for the most part and are easy to spot.
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.
Boring insects - are truly horrible pests.
One that is often missed! Virtually all woody plants and trees are subject to borer attacks. If you're growing bonsai trees, you can have borers!
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.
Look for small holes in the trunk or limbs with fine "sawdust" directly beneath them.
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!
Every once in a while you may come across something really odd, be sure to check it out! One example that rarely shows up is
When it does appear, it can be devastating. Nashia inaguensis is one species it is particularly attracted to. See a full description on that page.
Another disaster in the making ... (other than "bugs") is a vegetarian critter called vole, no, not mole.
Guest Author Lee Squires wrote an article of 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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