How to Control Scale Insects on Outdoor Plants

Scale insects are sucking insects that weaken plants by sucking the sap from the tender plant tissues. Leaves yellow and drop and eventually the plant will die if not controlled. Here's how to treat scale on your outdoor plants.

Difficulty:

Moderately Easy

Instructions

Things You'll Need

• Chilocorus Nigritus
• Lindorus Lophanthae
• Coreopsis Plants
• Dill Seeds
• Garden Shears
• Horticultural Oils
• Pyrethrin
• Sponges
• Fennel Seeds
• Insecticidal Soaps

1. Know what you're looking for. Scale insects resemble round or oval 1/10- to 1/5-inch bumps without legs. They are hard to spot unless you look very closely.

2. Look for scale insects on the undersides of leaves year-round. They gather in clusters near leaf joints and on leaves and soft stems. The scale secrete a large amount of honeydew onto the foliage, which causes sooty mold, a black fungus, to grow. Black leaves and stems are also an indication of scale insect infestation.

3. Prune and dispose of infested branches and twigs.

4. Attract predatory beetles, such as soldier beetles and ladybugs, to your garden by planting coreopsis, dill, fennel and nectar plants such as salvia.

5. Remove scale insects from plants using a soft cloth or sponge dipped in insecticidal soap. Rinse with plenty of fresh water after washing the plant.

6. Purchase and release Chilocorus nigritus or Lindorus lophanthae beetles or Metaphycus helvolus, a parasitic wasp.

7. Spray a mixture of insecticidal soap and horticultural oil to control scale insects. The oil smothers the slow-moving insects.

8. Spray pyrethrin as a final resort. Pyrethrin is an organic pesticide made from a chrysanthemum. There are also chemical pesticides available.

Tips & Warnings

• Always try the least toxic method of pest control as your first step.

• If you use chemical pesticides in your garden, you will also kill the natural predators of scale insects.

• If you choose to use a chemical method of control, always wear protective clothing and safety gear, including a long-sleeved shirt, long pants, neoprene gloves, goggles and a respirator.