Darrell Blackwelder: Whiteflies are making your shrubs ugly

Published 12:00 am Sunday, May 5, 2019

Many flowering shrubs are in full bloom looking their best in years. However, some shrubs are developing unsightly foliage. Gardenias, camellias and other shrubs have a black, sooty mold covering the upper surface of their foliage.

Closer observation reveals the shrubs are inundated with tiny, white insects by the hundreds. Whiteflies emerge as clouds of tiny white moth-like insects when the leaves are disturbed.  These are common insects that gravitate toward gardenias and other landscape plant materials. These minute insects also affect poinsettias and vegetables such as pepper and tomatoes.

These pests normally do not kill shrubs but will weaken them contributing to unsightly sooty, black, yellowing leaves. Controlling the insect can be difficult because the eggs and immatures are found on the underside of the leaves. Hosing the leaves regularly with water will greatly reduce infestations. Insecticidal soap and horticultural oils are helpful in controlling the insect.

Application of these oils in conjunction with systemic insecticides work best for complete control. It’s very important to spray both the upper and lower portion of leaves with repeated applications over the summer. For more detailed information, go to https://content.ces.ncsu.edu/insect-and-related-pests-of-flowers-and-foliage-plants/whiteflies-found-on-flowers-and-foliage.

Darrell Blackwelder deblackw@ncsu.edu is retire horticulture agent with the North Carolina Cooperative Extension Service in Rowan County.