Lake County Fact Sheet 2015006

Viburnum Viburnum spp.

General Information

There are several species of viburnums that grow in Central Florida including V. obovatum (Walter’s vibur-

num 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 sum-

mer. 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.

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

Photo: V. odoratissimum, J. Popenoe

Photo: Downy mildew on V. suspensum. Florida Division of Plant Industry Archive,

Florida Department of Agriculture and Consumer Services, Bugwood.org

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.

Spider mites Recognition: Spider mites are tiny, eight-legged pests generally found on the undersides of the leaves. South-

ern 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.

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.

Contributing factors: Thrips pop-

ulations 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 in-

festations.

Management recommendations: Control of severe infestations may

require use of approved insecticides.

Several biological controls are being

investigated. See http://

mrec.ifas.ufl.edu/lso/thripslinks.htm for the latest details.

Photo: Southern Red Mite, R.F. Mizell

Photo: Chilli thrips damage, L. Osborne

Photo: Greenhouse thrips damage,

University of Florida

Photo: Adult Chilli thrips on left, flower

thrips on right. L. Osborne

Photo: Ants and aphids, J. Popenoe

Photo: University of Florida

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, mid-

June 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.

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 honey-

colored mushrooms can sometimes be observed emerging from the trunk

or roots nearby.

Contributing factors: Mushroom root rot is a wood rot fungus which col-

onizes old roots and stumps as well as living plants. This disease often oc-

curs 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.

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

Photo: University of Florida

Lake County Fact Sheet 2015006

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.

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. Universi-

ty 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

Photo: Mushroom root rot mycelium., University of Florida.