by Dave Bogan

This article fi rst appeared in the August 2003 Evansville Bonsai Society Newsletter. It was recently republished in the August 2005 Potomac Bonsai Association Newsletter. - ED

This is the top season for the deadly and hard-to-see spider mite. These little mites - not true insects - actually are arthropods and related to the spider. True insects have three body segments while mites have eight legs and only two body segments. Since they are not true insects, many insecticides have little effect on them.

Spider mites attack a plant by piercing leaf tissues (or needles in the case of junipers) and sucking the green liquid that oozes out. The leaf tissue then looks brown after it has lost its green color. Quickly killing the affected foliage. Heavily infested leaves and branches can become covered with an almost invisible webbing - another telltale sign of their presence - examine your plants in early morning when the dew is still on.

A good way to determine that these mites exist is to hold a piece of white paper under the branch, and tap the branch sharply. If present, the mites will drop off and you will notice some of the spots on the paper moving.

The most common mite to our area [Evansville, IN] is the two-spotted spider mite (so called because under a magnifying glass, you will see two dark spots on each side of its abdomen). This type of mite feeds on more than 150 flowers, vegetables, and woody ornamentals.

Spider mites have a very short life span, but they reproduce quickly. When our temperatures reach into the 90's, the mite population can more than double every three days.

A regular inspection of your trees is imperative now. Spider mites also thrive on plants under stress. This stress may come from under-watering, or damaged foliage or root systems. One easy control is to continually wash the foliage down. Mites cannot live in a wet environment. Moisture will create a fungus disease which kills them. So keeping a moisture balance can help. Now, do not over-water the soil, just keep the foliage moist. By washing down your foliage every [or every other] day, you also wash out many mites along with the dreaded aphids and scale. I generally wash down my foliage in late evening during my normal waterings. As mentioned, don't confuse watering the foliage with watering the soil. Insecticidal soap is a good control agent. I now use a product called Pyola and so far this year, no mites. The Pyola is a light oil (canola) which encapsulates and smothers the mite and its eggs while not affecting many of the "good" insects which may fly by.

Pyola insect spray.

A broad-spectrum organic spray that combines pyrethrin (a long popular insecticide derived from pyrethrum flowers) and canola oil (extracted from rapeseed). Unlike most pesticides, it controls all stages of an insect's life cycle, including eggs. [One pint makes 12 gallons for ~$17.] [I could not find Pyola locally at any of the garden centers. I did find it on the internet at www.gardensalive.com -ED]

With most pesticides, the problem is usually timing. The fact is, some insecticides control adult insects while others kill larvae. Many oil-based sprays will suffocate eggs, but are ineffective on hatchlings. Unless you can match the spray with the life cycle, it will be ineffective. The beauty of Pyola is it will simultaneously attack adult insects as well as larvae and eggs. Another good point is it will last for days, discouraging other insects from feeding and laying eggs. Additionally, this spray is not harmful and can even be used on fruits and vegetables right up to harvest time.

This spray is good against many types of insect including, but not limited to, ants, aphids, scale, beetle larvae, fungus gnats, mealybugs, mites, spider mites, and whiteflies, plus caterpillars, tent caterpillars, and Japanese beetles.