Spider Mite Damage to a Japanese Aralia

Damage Identification

• Spider mites often affect a Japanese aralia during summer months, especially when conditions are dry. In addition to the silky webs spider mites spin over leaves and branches, you probably will see changes in leaf color. Look for foliage that first displays tiny dots in which the leaves take on a lighter color; the color change may progress to a bronze hue, resulting in a scorched appearance. The damage leads to red or yellow leaves and defoliation. Severe cases may result in plant death.

Pest Identification

• Spider mites are sucking bugs that feed on leaf plant sap. Although these 1/20-inch long pests may appear to be moving specks, the webs they spin may indicate their presence. Up close, the eight-legged pests resemble spiders with oval-shaped bodies. Spider mites typically appear during periods of high temperatures from summer through the beginning of fall.

Control

• Controlling spider mite problems in a Japanese aralia requires always maintaining moist soil for the shrub. A thirsty, stressed plant is more likely than a well-watered plant to experience a spider mite infestation and subsequent damage, according to a University of California Integrated Pest Management Online article. Because the use of chemical insecticides and miticides can result in a more severe problem than initially existed, skip chemical control of the spider mites and focus on biological options. Attempt to push mites from the plant with a strong spray of water. Releasing spider mites' natural enemies, such as spider mite destroyers (Stethorus species) and western predatory mites, can help to control the pest population.

  Remove and destroy severely affected plant parts by pruning them into a plastic zipper bag. After sealing the bag, it should be placed in a trashcan. Remove and destroy the entire plant if the infestation and damage is extreme. In an extreme circumstance, however, a botanic pesticide, such as horticultural oil, can be applied to the plant to try to save it. Mix and apply horticultural oil according to the directions on the product's label; instructions typically suggest mixing 5 tablespoons of the oil per 1 gallon of water. Saturate the plant, spraying it once monthly; do not apply horticultural oil, however, if temperature exceeds 90 degrees Fahrenheit.

Prevention

• Avoiding damage from spider mites is often as simple as providing consistent care for your Japanese aralia. A well-maintained plant has a greater ability to resist pest infestations than a plant that doesn't receive proper care. Grow your Japanese aralia in an area of the garden that offers full to partial sun exposure. Maintain moist, well-drained, acidic soil high in organic content for the shrub.