Q. Help! My plants are turning black and I found some white stuff on the underside of the leaves. What’s going on?
K.G., Key West
Based on the photo you sent, your plants are infested with the rugose spiraling whitefly. It used be known as the gumbo limbo spiraling whitefly.
Don’t panic: The rugose spiraling whitefly is different from the ficus whitefly in that it is less of a pest to plants. So far, it is not causing severe damage such as plant death or branch die-back. But it is a nuisance and can create a mess.
To determine if your plants are infested, look for the distinctive white spirals and a build-up of a white, waxy substance on the underside of the leaves.
If populations build up, infested plants can become covered with the white, waxy substance and disfigured by the black sooty mold that grows on the insect’s excrement (called honeydew). The sticky honeydew can accumulate on cars, pool decks and patio furniture from infested trees.
Once the insect is under control, the sooty mold and honeydew will disappear.
To control this pest on small plants, thoroughly wash off plants with a strong stream of water from your hose. Follow up with an insecticidal soap or horticultural oil sprayed on the underside of the leaves once a week for three to four weeks. These products are found at garden centers.
For heavily infested larger plants and shade trees, thoroughly wash plants off with a strong stream of water. In some cases, you may want to consider using a systemic insecticide (labeled for whitefly control on landscape plants). Systemics are applied to the soil as a drench, granule, tablet or as a trunk injection. You can hire a professional to perform the trunk injection.
Always follow the label directions since the “label is the law”.“Tree & Shrub Insect Control” is a commonly sold systemic available at garden centers and home improvement stores.
Systemics may take several weeks to be effective for large trees but are long-lasting (9-12 months). The most efficient time to apply systemic pesticides is late spring or at the beginning of the rainy season so that the product will be in the leaves at the time when the whitefly population starts to increase.
If your fruit tree is infested, call your County Extension office for recommendations, since most pesticides are not labeled for tropical fruit trees. Whiteflies can be wiped off banana leaves with a cloth.
To learn more about this pest and other pests, visit these websites: http://miami-dade.ifas.ufl.edu/ and http://solutionsforyourlife.ufl.edu/