Landscape, Nursery, and Greenhouse - Whiteflies

The following is information on whiteflies that you may see on plants in Delaware.

Whiteflies affect both woody and herbaceous plants. Whitefly damage starts with yellowed foliage follwed by honeydew/sooty mold. Almost all stages, except the egg and last nymphal stage (aka “pupae”) feed. The following represents a few of the common whiteflies in our area, their level of impact and ID tips.

Azalea/Rhododendron Whitefly (Pealius azaleae, Dialeurodes chittendeni) Occasional pest that causes leaf cupping and minor leaf yellowing. Nymphs/”Pupae” orange to yellow. Nuisance clouds of dusty colored adults can be heavy at times.

Banded Winged Whitefly (Trialeurodes abutilonia) Adults hold wings “peaked” over body (similar to silverleaf whitefly), with two dark grey bands on each wing. “Pupae” slightly brownish in color. Often found on yellow sticky cards, but cause no damage to most ornamentals.

Greenhouse Whitefly (Trialeurodes vaporariorum) Common, many hosts affected. Live nymphs yellow. Differ from silverleaf whitefly--adults fold wings flat on top of their body and “pupae” resemble “fluffy pancakes” with raised sides. Often require management.

Mulberry Whitefly (Tetraleurodes mori, T. ursorum) Affect mulberry, citrus, Mahonia and a few other woody species. Nymphs are black surrounded by a white fringe. Rarely more than a curiosity.

Silverleaf (Sweetpotato) Whitefly (Bemisia argentifolii, B. tabaci) Common, many hosts affected. Nymphs yellow colored. Differ from greenhouse whitefly--adults fold wings flat on top of their body and “pupae” resemble “yellow water droplets” without any raised sides. Very common on recently purchased or introduced plants. Require management. New Biotype Q of this pest resistant to many standard pesticides, esp. Distance (pyriproxifen) and neonicotinoids.

For whitefly species requiring management, choose selective products that target specific life stages like horticultural/neem oils and IGR's for nymphs, Beauveria or neonicotinoids for late nymphal stages, and target adults only if necessary with pyrethroids. Predators and parasites exist in the landscape environment or are available to purchase for greenhouse/nursery environments. Look for black “pupae” in Greenhouse/Silverleaf whitefly infestations that indicate parasitism.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens