Pests in Gardens and Landscapes: Quick Tips
Adult giant whiteflies.
Giant whitefly eggs, nymphs and adults on the underside of a leaf.
Beardlike wax strands.
Healthy yellow whitefly nymph surrounded by black ones that have been parasitized, including one with an exit hole at right.
Giant whiteflies can cover a beautiful plant with white fuzzy wax and sticky honeydew, turning it into an unsightly mess. First discovered in San Diego County in October 1992, this whitefly has spread northward into other areas of California. Although affected plants may be weakened, they rarely die. To manage giant whitefly, wash off plants with water and encourage natural enemies.
What plants are affected?
- Many ornamentals including hibiscus, giant bird of paradise, begonia, Xylosma.
- Fruit trees including citrus, avocado, mulberry and banana.
Look or these damage symptoms on affected plants:
- Long, white, waxy filaments produced by the whitefly give the leaf surface a bearded appearance. These hairlike strands may be mistaken for a fungal infection.
- Large amounts of sticky honeydew excreted by the whitefly as it feeds on plant sap.
- Black sooty mold growing on the honeydew.
How to recognize the whitefly:
- Adults are small (3/16 inch long), white with light brown markings on their wings, and usually found in groups on the undersides of leaves.
- Nymphs are yellowish, small, oval, have no legs, and don't move.
To reduce problems, use an integrated program that includes:
- Removing infested leaves.
- Washing giant whiteflies off leaves with a strong stream of water.
- Planting species less susceptible to giant whitefly.
- Avoiding insecticides that injure natural enemies, such as lacewings, lady beetles, syrphid flies, and parasitic wasps.
What about insecticides?
- Don’t use insecticides if beneficial insects, including parasites and predators, are present in the area.
- To confirm the presence of parasitic wasps, use a magnifying glass to look for parasite exit holes on giant whitefly nymphs or darkened nymphs (see photo).
- If you do choose to use an insecticide, select least toxic products such as insecticidal soaps or oils. Spray the undersides of the leaves where whitefly colonies are found.
- Remember to follow label directions.
Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.