Bonsai Pests Aphids

Bonsai pests include any pests you may find on other plants. One such common problem is the aphid.  Bonsai are definitely not immune.

While working on a Podocarpus bonsai with a client, I discovered a bad infestation of blue ones. That’s right blue! I later discovered they are actually called Podocarpus Aphids – Neophyllaphis podocarpi.  

Sometimes called ’plant lice’, aphids may infest almost any plant. They have piercing mouth parts and cause damage by sucking the plant juices.

Their ability to transmit plant virus diseases may be more harmful than any actual feeding damage.

Aphids are soft bodied pear shaped insects usually less than 1/8 inch long and mostly green in color, but many are yellow, blue, white or red as shown here.  They are commonly found on the stems or undersides of leaves.

Most aphids are wingless but when colonies become overcrowded or the host plant becomes undesirable, winged forms are produced which establish new colonies.

Aphids are unlike most other insects in two ways:

  • Almost all are females and reproduce without mating, and
  • They seldom lay eggs, but give birth to living young.

The scariest part – aphids have the ability to reproduce rapidly and there are many generations per year.

The Ant Connection

This pest excretes large amounts of honeydew  which provides an excellent medium for the growth of a black fungus called ‘sooty mold’.

Besides being unattractive, sooty mold interferes with photosynthesis and can retard the growth of the plant. Sooty mold usually weathers away when the insect infestation is removed.

A little scrubbing with an old toothbrush and soapsuds will also aid in removing sooty mold.

Weird, but true!

Aphids hold onto their honeydew until an ant taps them on the backside with her antennae, at which point the aphid releases droplets of honeydew for the ant.

Ants feed on the honeydew.  When ants are observed, plants should be examined closely for these sucking pests.  If you have ants, you likely have aphids. They may be one of your most problematic bonsai pests, especially if you are an indoor grower.

Non-Insecticidal Management

Many growers are able to remove aphids by simply spraying their trees with a forceful stream of water.  You can use this same procedure for your bonsai.  Use a garden hose with an adjustable nozzle and be sure to spray undersides of leaves and stems.

Insecticidal Management of Bonsai Pests

Aphids are not difficult to manage without insecticides, however, plants may become re-infested from adjacent areas throughout the year. For management, apply a recommended insecticide if aphids are beginning to re-infest the plants.

For bad infestations, spray the plants to the point of run-off. Be especially careful to cover the undersides of the leaves and all parts of the twigs thoroughly.

Important: When using any type of chemical on your bonsai, test one area first.

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