Viburnum - Lake County Extension

Lake County Fact Sheet 2015006
Viburnum
Viburnum spp.
Photo: V. odoratissimum, J. Popenoe
General Information
There are several species of viburnums that grow in Central Florida including V. obovatum (Walter’s viburnum which comes in dwarf and standard forms), V. odoratissimum (sweet viburnum which also has a shiny,
large-leaved variety Awabuki), and V. suspensum (sandankwa viburnum). The species vary in susceptibility to
pests and diseases.
Propagation
Cuttings – V. odoratissimum is usually propagated by semi-hardwood secondary cuttings taken in early summer. The cuttings should still be hairy. Rooting should occur in 6-12 weeks under low light and intermittent
mist when wounded cuttings are used.
V. suspensum is usually propagated by semi-hardwood secondary cuttings collected at any time. Rooting
should occur in 6-8 weeks with intermittent mist and high water volume.
Pests and Diseases
The current Insect Management Guide for Commercial Foliage and Woody Ornamentals can be found at
http://edis.ifas.ufl.edu/IG012. The current Professional Disease Management Guide for Ornamental Plants can
be found at http://edis.ifas.ufl.edu/PP123.
Downy mildew (Plasmopara viburni)
Recognition: Leaf spots and defoliation. White powdery areas may be seen
on the underside of the leaf.
Contributing factors: Cool, humid nights. The disease seems to affect
Awabuki and sandankwa more than others.
Management recommendations: Refer to the Disease Management Guide
for the latest preventive chemical recommendations. Cultural controls
include keeping leaves dry and increasing air movement.
Photo: Downy mildew on V. suspensum. Florida Division of Plant Industry Archive,
Florida Department of Agriculture and Consumer Services, Bugwood.org
Aphids
Recognition: Aphids cluster and feed on new growth, causing leaf curling and distortion. Aphids have small,
pear-shaped bodies with paired cornicles (look like dual exhaust pipes on the rear). Aphids excrete honeydew
on which sooty mold grows. Ants will farm and protect the aphids in order to harvest the honeydew.
Contributing factors: Aphids are usually most numerous in the spring, but may be present throughout the
Lake County Fact Sheet 2015006
growing season.
Management recommendations: Aphid mummies are a sign that natural
biological control is occurring. High populations may be treated with soaps,
oils, or other approved insecticides.
Photo: Ants and aphids, J. Popenoe
Photo: University of Florida
Spider mites
Recognition: Spider mites are tiny, eight-legged pests generally found on the undersides of the leaves. Southern red mite is the most common on viburnum. Mite feeding causes a stippled
or bronzed appearance of the leaves.
Contributing factors: Southern red mites are most numerous in cool weather.
Management recommendations: Use a white piece of paper and/or a hand
lens to monitor for mites. Check for the presence of predatory mites, which
are larger and mover faster. Use insecticidal soaps, oils, or approved miticides
if necessary.
Photo: Southern Red Mite, R.F. Mizell
Thrips
Recognition: Greenhouse thrips cause a flecked, bleached, silvered or russeted appearance to viburnum
leaves. Spots of shiny black excrement are visible. The adults are tiny
(<3/64 inch) and black; nymphs are translucent. Chilli thrips damage
looks more like scarring that causes leaf distortion. Chilli thrips are
smaller than most thrips and are yellow colored.
Photo: Chilli thrips damage, L. Osborne
Photo: Greenhouse thrips damage,
University of Florida
Contributing factors: Thrips populations are at their peak during the
spring months. Greenhouse thrips
prefer shade and are weak flyers so
infestations tend to be very localized.
Chilli thrips hide in the leaves and
buds, but can cause widespread infestations.
Management recommendations:
Control of severe infestations may
require use of approved insecticides. Photo: Adult Chilli thrips on left, flower
Several biological controls are being thrips on right. L. Osborne
investigated. See http://
mrec.ifas.ufl.edu/lso/thripslinks.htm for the latest details.
Lake County Fact Sheet 2015006
Whitefly
Recognition: The tops of the leaves become pale or spotted due to feeding by whiteflies; sooty mold also
grows on the sugary substance excreted by the whiteflies. Whiteflies resemble tiny white moths, and the adults
will fly when the plant is disturbed, then re-light on the leaves. Their bodies are covered with a powdery wax.
The silverleaf whitefly tends to fold its wings at an angle over its body, while the citrus whitefly holds its
wings flat over its back, but it is difficult to tell them apart. Nymphs are translucent yellow ovals that are often
confused with scale insects. They are mobile for the first part of their life, then insert their mouthparts into the
leaves and remain stationary until they pupate.
Contributing factors: There are three generations of citrus whiteflies per year, typically in late March, midJune and late August.
Management Recommendations: Parasitic wasps assist in keeping whitefly populations under control. Wasp
parasitism can be recognized by round emergence holes in the pupae, rather than T-shaped holes made by
emerging whiteflies. Various biological controls can be seen at http://mrec.ifas.ufl.edu/lso/Whitelfies.htm. The
silverleaf whitefly is more difficult to control than the citrus whitefly. Alternate classes of insecticides to avoid
resistance. Check the IFAS Insect Management Guide for specific recommendations.
Photo: Whitefly 4th instar, L. Osborne
Photo: Silverleaf whitefly, L. Osborne
Photo: Parasitic wasp with whitefly
pupae., L. Osborne
Photo: Emergence hole in
parasitized whitefly “skin”,
L. Osborne
Mushroom Root Rot (Armillaria tabescens)
Recognition: Mushroom root rot causes a slow decline and thinning plant
canopy. Desiccated foliage on affected stems has a gray-green coloration..
One or more stems may be killed. Bark removal at the base of the plant
will reveal white, mat-like fungal growth (mycelium). Clusters of honeycolored mushrooms can sometimes be observed emerging from the trunk
or roots nearby.
Photo: University of Florida
Contributing factors: Mushroom root rot is a wood rot fungus which colonizes old roots and stumps as well as living plants. This disease often occurs when plants reach old age. It can spread from one plant to others
nearby through root grafts.
Management recommendations: There is no control for this disease. Remove the diseased plant as well as
adjacent ones in a hedge. Remove roots and soil and replace with clean topsoil before replanting.
Lake County Fact Sheet 2015006
Photo: Mushroom root rot mycelium., University of Florida.
Sources:
1. Caldwell, D. 2011. Viburnum Downy Mildew Disease on Awabuki (Mirror leaf) Viburnum. http://
collier.ifas.ufl.edu/CommHort/CommHortPubs/Viburnum%20Downy%20mildew%20disease%20March%
20%202011_D%20Caldwell.pdf. Accessed 9/11/15.
2. Foerste, E., C. Neal and C. White. 2004. Key Plants and Key Pests in Central Florida Landscapes. University of Florida/IFAS.
3. University of Florida Landscape Plant Propagation Information. http://hort.ifas.ufl.edu/database/lppi/
index_scientific.shtml#V. Accessed 9/11/15.
Prepared by:
Juanita Popenoe, PhD
Lake County Extension
1951 Woodlea Rd.
Tavares, FL 32778-4052
Tel.: (352) 343-4101
September 2015
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity—Affirmative Action Employer authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status,
national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative
Extension Program, and Boards of County Commissioners Cooperating.