How to Kill Spider Mites on Bonsais
Nothing can stress the keeper of a bonsai specimen more than pests attacking his pride and joy, particularly if they’re spider mites. While severe infestations of these tiny eight-legged terrors can literally suck the life out of a plant and kill it, small populations aren’t difficult to eliminate. The key is to diagnose the problem quickly. Treat your bonsai proactively and aggressively with nothing fancier than what you probably already have around the house. Even badly damaged plants often recover once they’re completely rid of spider mites.
Examine your bonsai’s overall appearance daily for the presence of spider mites. Junipers and other conifers will exhibit tiny yellow spots on their needles, which may even turn brown and drop off as a result of spider mite predation. Leafy bonsai specimens suffer tiny yellow spots called stippling on the foliage. Leaves wilt, yellow along the veins and begin dropping as spider mite damage increases. The health of an untreated plant declines, and it will eventually die.
Place a sheet of white paper on a flat surface under the bonsai’s branches. Tap a limb gently but firmly. If spider mites are present, you’ll see the tiny, black or red pests scurry around on the paper. Repeat until you have tested all the bonsai’s branches.
Scrutinize the mid-veins on leaf undersides with a magnifying glass as spider mites are so tiny that they’re difficult to see with the naked eye. Search thoroughly for the mites, which look like very tiny grains of black or red pepper. Check petioles and branch crotches closely for fine silken webbing.
Isolate the infested bonsai from all other plants immediately. Spider mites spread easily from plant to plant and produce an astounding 50 to 200 eggs every seven to 14 days in favorable conditions.
Add one gallon of warm water to a bucket. Pour in 5 Tbsp. of non-degreasing liquid dish soap to create a 2 percent solution of insecticidal soap. Stir the solution gently to combine well without creating excessive suds. Add the insecticidal soap to a plastic spray bottle.
Spray all surfaces of the bonsai to the point of runoff. Pay special attention to the undersides of leaves. Insecticidal soap kills all the spider mites it covers. Do this outdoors in the morning on a calm day when you expect the temperature to remain below 90 degrees Fahrenheit. To prevent a possible hypersensitive reaction to the solution, rinse the bonsai thoroughly to remove all traces of soap.
Check the bonsai carefully each day for the presence of live spider mites. Repeat the insecticidal soap every four to seven days until the plant no longer tests positively for the pests. Keep it quarantined for another week and test once more before returning it to your collection.
- Mist the bonsai daily to increase the humidity in the environment. Spider mites thrive in warm, dry conditions typical of homes and offices. Cover the bottom of a saucer with gravel. Add enough water to nearly cover the small stones and set the bonsai’s pot on top of them. Do not allow the plant’s roots or the potting medium to come in direct contact with water. This further increases the amount of humidity in the air.
- Pick up any dropped plant material, which is probably infested with spider mites or their eggs. Wrap it up in a plastic bag and dispose of in the trash.
- Test the soap solution on a small area on the bonsai before using it as an all-encompassing insecticide. Check the area for signs of trouble in 48 hours.
- Plants that tend to be hypersensitive to soap include succulents, crown of thorns, nasturtiums, ferns, lantana, palms, some ivy cultivars, gardenias, hairy-leafed plants and some types of tomatoes.
A full-time writer since 2007, Axl J. Amistaadt is a DMS 2013 Outstanding Contributor Award recipient. He publishes online articles with major focus on pets, wildlife, gardening and fitness. He also covers parenting, juvenile science experiments, cooking and alternative/home remedies. Amistaadt has written book reviews for Work At Home Truth.