Root Mealy Bugs

Many years ago I discovered root mealy bugs in a bald cypress bonsai. At first, I thought it was mycorrhiza.

Mycorrhiza is a useful root fungus, especially helpful to conifers. They look very similar.

However, this pest - Rhizoecus americanus (Pseudococcidae Family) - is related to scale. It is a soft-bodied, sucking insect that attacks the tips of roots (new growth).

They are sometimes called “blind or soil” mealies.

What They Look Like

Similar in appearance to the familiar above ground mealy bug, they both leave white waxy secretions in their wake -- like small bits of cotton.

Rhizoecus is primarily a warm climate pest. It is very common in Florida and other southern states.

However, if shipped in plants, it continues to thrive indoors and in greenhouses.

These creatures are dangerous to your plants and are often ignored as insignificant or misidentified as mycorrhiza. They are neither!

If you are in doubt, the ideal way to identify them is through a microscope or magnifying glass.

What you will see is the graphic shown here. (100X real life)

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Symptoms and Detection

An important part of taking care of bonsai trees is to observe them on a regular basis.

In this case, leaves may be pale (sometimes grayish) or wilted, despite regular fertilizer and watering. Maybe the plant growth has slowed down and/or flowering has ceased. In severe cases, the leaves may be misshapen.

To detect root mealy bugs in a well-established bonsai, gently lift it out of its container and look at the sides and bottom of the root mass. Many times you need to search no further.

Although they occur throughout the roots, they are most obvious along the edges. They can also appear on the inside walls of the container and sometimes even underneath the pot.

Also, while pulling weeds, observe any soil that may come up with them.

I have seen bad infestations continue out of containers onto old wood nursery benches!

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What To Do

Spraying chemicals or even repotting is often not sufficient to eliminate them!

When I found this pest in a forest planting, I knew what it was right away and called the County Extension Service to find the current recommendation for treatment.

The Answer: Bayer Advanced 12 month Tree & Shrub Protect and Feed

I immediately sprinkled the granules on the affected bonsai plant.

Bayer Advanced is available at most garden centers and well worth the price!

If you don't have many plants, you may find this valuable product a little pricey. Consider sharing the large container with a friend.

Where to Go From Here

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Read about other Bonsai Plant Pests