Pests and Diseases

Pests and diseases are common problems when growing flowers and ornamentals. They can cause both direct and indirect damage that can be costly. Use Penn State Extension’s extensive resources to find out more about managing flower pests and diseases, including Fletcher scale, leafhoppers, spotted lanternfly, webworms, mites, caterpillars, pillbugs, weevils, scales, borers, beetles, aphids, moths, blight, necrosis, root rot, and freeze damage.

Common Flower and Ornamental Diseases

Being able to accurately diagnose pests and diseases is crucial if you want to control them and get the best results from your flowers. Learn how to recognize and distinguish between symptoms and signs of stress, including damage and diseases, and you’ll be able to employ best management practices.

Scouting is an excellent way to identify and manage plant diseases, pests, and problems afflicting your ornamentals and flowers.

Use Penn State Extensions resources to help identify diseases that affect some of the most popular plants. Here are some examples:

• Roses: Blackspot, anthracnose, cankers, and downy mildew
• Pansies: Cercospora leaf spot, fusarium wilt, scab, and pythium root rot
• Echinacea: Alternaria leaf spot, aster yellows, foliar nematode, and white smut
• Narcissus: Basal rot, lesion nematode, scorch, stem and bulb nematodes
• Tulips: Fire, viruses, root rot, stem and bulb nematode
• Begonia: Bacterial leaf spot and blight, botrytis blight, foliar nematode, and powdery mildew
• Chrysanthemums: Ascochyta ray blight, bacterial blight, bacterial leaf spot, and chlorotic mottle
• Poinsettia: Ammonium toxicity, bacterial canker, bacterial stem rot, and botrytis stem canker
• Azalea and rhododendron: Botryosphaeria canker, botrytis blight, cylindrocladium blight, leaf, and flower gall
• Hostas: Anthracnose, petiole rot, bacterial soft rot, and hosta virus
• Boxwood: Decline, blight, leaf burn, and leaf spot
• Juniper: Cedar-apple rust, cercospora blight, twig blight, and Japanese apple rust
• Palms: Cold injury, fluoride injury, helminthosporium leaf spot, and leaf burn

Pests on Flowers and Ornamentals

Do you know what to look for when it comes to insect pests on flowers and ornamentals? Learn about the life cycles of pests and your management options, including Integrated Pest Management (IPM) practices and pesticides on Penn State Extension’s Landscape Pest Identification Walk.

If you know what insects, mites, and diseases to look for, it will help you decide whether pesticide application is the best course of action. There are some common pests you should be aware of:

• Japanese beetle: Can cause significant damage to turfgrass and ornamental plants.
• Spotted lanternfly: An invasive insect that feeds on the plant sap of many different plants such as maples, black walnut, and grapevines.
• Lace bug: They have recorded 28 lace bug species in Pennsylvania, but only a few are pests of ornamental plants.
• Aphids: Some species feed on foliage, while others feed on twigs and branches, flowers or fruits.
• Fletcher scale: This is a common pest of arborvitae and yew, but it can also attack juniper, cypress, and hemlock.

Biocontrols and Pesticide Application in Floriculture

There are several ways to control pests and diseases. Traditionally, pesticides have been used to control pests in floriculture. We still use them today, not quite as much, but especially when pest populations have rapidly expanded or were detected late and need to be quickly brought under control. The four most common types of pesticides are synthetic, natural, organic, or chemical.

Homeowners can apply pesticides themselves or take advice from a professional pest manager. If restricted-use pesticides are being applied, the applicator must be certified. Private Pesticide Applicator Short Courses and Commercial Applicator Short Courses are available, in both Spanish and English, for anyone who wants to apply restricted-use pesticides on their farm or property. Commercial Applicator Short Courses are also available for landscapers applying pesticides to their customers’ properties.

An increasing number of homeowners and green industry professionals are using Integrated Pest Management to manage pests. IPM is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage employing a combination of techniques such as the use of resistant varieties, habitat manipulation, modification of cultural practices, and biological control.

Biological controls include beneficial insects such as ladybird beetles, green lacewings, and aphidoletes. Biopesticides are also used; these are pesticides that are derived from natural materials such as animals, plants, bacteria, fungi, and certain minerals.