Magnolia Parasites

Scale Insects

• Scales are parasites living, breeding and feeding on plant hosts such as magnolias. These tiny pests measure only about 1/2 inch in diameter with a brown, orange, or pink-colored body. Depending on the species, scales may have a light-colored waxy or powdery appearance. Female scales are wingless, while male scales have wings but are rarely seen since their lifespan is only a few short hours. Scales are sap-sucking insects that use their slender mouthparts to pierce the magnolia and suck its sap.

Scale Damage

• As scales feed on the magnolia, leaves begin to wilt, discolor and distort, and -- in large infestations -- can fall from the branches prematurely. Their feeding can also take its toll on the overall health of the plant, leading to loss of vigor and poor growth. Scales also produce a sticky secretion known as honeydew when they feed on plant sap. This substance attracts ants -- which feed on the sticky liquid -- and leads to sooty mold growth. Sooty mold is a fungus that has the appearance of black soot. Even though sooty mold doesn’t harm the magnolia directly, it can cover the leaves and prevent them from engaging effectively in photosynthesis.

Pesticides for Scales

• Chemical-filled insecticides used to control insects often have an adverse effect by killing off beneficial predatory insects that keep scales and other pests under control. Always choose natural control options for scale management if possible. If, however, you decide to use pesticides to control scales, use horticultural oil, neem oil or insecticidal soap. These leas-toxic insecticides have a low toxicity level to beneficial insects, wildlife, pets and humans. The application for these safer pesticides varies depending on the type and brand used. For example, one type of horticultural oil requires mixing 5 tablespoons in 1 gallon of water while one brand of neem oil suggests 2 tablespoons per gallon of water. This diluted pesticide is sprayed on the trunk, leaves and branches of the magnolia once every seven to 14 days as needed.

Control Scales Naturally

• The best defense against scale is to utilize natural management options such as predatory insects. These beneficial insects prey on the scale keeping their numbers in check. Unfortunately, predatory insects cannot always control large infestations of scale and you may have to first treat the magnolia with safe insecticides before attracting beneficial predators to your garden. Planting enticing flowers will help lure the beneficial predators back to the area. Annual herbs with fragrant flowers -- such as dill (Anethum graveolens) and basil (Ocimum basilicum) -- attract lady beetles, lacewings and parasitic wasps, which are all predators of scales.