Although many types of clematis attract beneficial insects like bees, these climbers can also attract pests or become infected by diseases. In my experience, clematis can suffer from diseases like clematis wilt, leaf spot, and powdery mildew. Pests like aphids, caterpillars, scale insects, and spider mites can also attack my lovely vines. I find the best forms of pest control are horticultural oils, insecticidal soap, and organic fungicides or pesticides. In this article, I’ll explain how to identify and tackle 11 common clematis pests, bugs, and diseases.
1. Clematis Wilt
Clematis wilt is one of the most severe fungal diseases that can infect clematis, particularly during the summer. Infected plants can wilt rapidly, causing them to collapse and die. Clematis wilt seems to affect large-flowered clematis varieties more than small-flowered cultivars.
Symptoms of clematis wilt include blackened, shriveled foliage or leaf stalks and leaf spot. Stems may also be blackened inside when split open. Cut back infected clematis foliage using clean, sharp tools so that young, unaffected shoots can grow.
2. Leaf Spot
Leaf spot diseases also infect clematis and can be confused with clematis wilt. This disease is caused by fungal infections that thrive in moist conditions with poor airflow. Symptoms of leaf spot include black or brown spots on foliage or lesions on stems.
Reduce the leaf spot risk by pruning your clematis at the right time of year to improve airflow around the plant. When watering your clematis, avoid getting water on the leaves and flowers.
3. Phytophthora Root Rot
Phytophthora root rot is a disease caused by spores of the Phytophthora fungus. These spores thrive in wet or waterlogged soil and cause root rot. Visible symptoms include dying or wilting foliage that is turning yellow.
The main clematis stem may appear darker around the soil line. Infected roots will appear black or brown and may also smell. Cut away infected roots and dispose of the infected soil safely. Replant the clematis in fresh soil and add extra drainage using grit.
4. Powdery Mildew
Powdery mildew is one of the most common clematis diseases. This disease thrives when hot and dry conditions emerge during the day and it’s cold and wet at night. Symptoms of powdery mildew include stunted growth and dusty white patches on clematis leaves.
Use organic copper fungicides or horticultural oils to combat powdery mildew. Promoting good airflow around your clematis helps prevent powdery mildew. Water in the morning to stop your plant from sitting in cold, wet conditions at night.
5. Rust Diseases
Clematis vines can also become infected with rust diseases, mainly affecting the foliage. Rust diseases are caused by fungi belonging to the Pucciniales group. Clematis infected with rust will develop brown, orange, or yellow pustules on the leaves.
Slow the spread of rust diseases by removing any infected leaves whenever you spot them. Providing the best possible growing conditions will help your clematis fight off or endure rust diseases without much damage. Fungicides are also an option, but use organic ones wherever possible.
Aphids are common garden pests that suck saps from leaves and stems. Colonies of black or green aphids often congregate underneath leaves or along stems. Aphid infestations may also cause black mold, deformed leaves, and stunted growth.
A quick blast from a hose can be enough to dislodge aphids. If the infestation persists, use biological control measures, horticultural oils, and insecticidal soap to remove aphids. Encouraging beneficial predatory insects like lacewings and ladybirds in your garden also helps control aphids.
The caterpillars of various species of butterflies and moths can feed on clematis vines. In most cases, picking off the caterpillars whenever you spot them prevents further harm. You can also encourage natural predators, such as birds in your garden because they will help you control caterpillar populations.
8. Leaf Miners
Leaf miners are various insect larvae species that burrow into plants’ leaves, like clematis. These pests leave behind visible twisting trails on infested leaves. Get rid of leaf miners using biological control measures, horticultural oils, and insecticidal soap.
9. Scale Insects
Like aphids, scale insects suck sap from host plants. Scale insects have waxy shells and lay groups of white eggs underneath leaves. Scale insects also excrete a sticky substance called honeydew, which can cause sooty black mold.
Biological controls, horticultural oils, and insecticidal soaps are usually enough to help you stay on top of a scale insect infestation. If your clematis is suffering from a large-scale insect infestation, use organic pesticides to eliminate the insects.
10. Spider Mites
Spider mites are a group of common pests that feed on the chlorophyll found in clematis leaves. Symptoms of spider mite infestations include white webbing and brown or yellow spots on the foliage or stems. Although there are several species, the symptoms are the same.
Avoid spider mites using horticultural oils, insecticidal soap, or biological control measures such as predatory mites. Most spider mite infestations won’t cause severe harm to clematis vines as long as the insects are kept in check.
Whiteflies are closely related to aphids and also suck sap from plants. These tiny white-flying insects can appear in large clouds whenever an infested plant is disturbed. Like scale insects, whiteflies also produce sticky honeydew that can develop into sooty black mold.
You can dislodge whiteflies using quick bursts of water from a hose. If the infestation is more serious, introduce biological control measures or use horticultural oils and insecticidal soap.
Pesticide and Insecticide Options and Solutions
Horticultural oils can interrupt the breeding cycles of several clematis pests, including aphids and scale insects. Canola and neem oils are two of the most common horticultural oils widely available in grocery stores or garden centers.
Insecticidal soap is an effective way of eliminating pests such as aphids. These soaps kill insects by dehydrating or suffocating them. If you can’t find insecticidal soap, you can create a similar solution by mixing dish soap with warm water.
Biological control methods involve using predatory organisms or insects to eliminate pests like aphids. Standard biological control measures include nematodes, predatory mites, and worms. Using biological control measures eliminates infestations without the need for chemical pesticides.
If your clematis is suffering from a fungal disease, fungicide is usually the easiest option. Although synthetic fungicides are available, try to use organic fungicides wherever possible. This reduces the risk of chemicals leaching into the soil or killing beneficial bacteria and insects.
If a pest infestation is severe enough, you may need to use pesticides. However, try and use organic pesticides rather than synthetic ones. Synthetic pesticides rely on chemicals that can leach into the soil around your clematis, killing beneficial bacteria.
Managing Common Clematis Pests and Diseases
Prevention is always the best cure for common clematis pests and diseases. And the best way to do that is by giving your clematis the best possible care.
Clematis grows in cool, temperate areas of the Northern Hemisphere and is relatively hardy in USDA Zones 4 to 9. Clematis vines grow best in full sun but can tolerate partial shade. Established clematis vines usually won’t need watering but water young plants regularly.
Clematis require fertile, well-draining soils that provide plenty of nutrients for flower growth. Loamy or silty soils are ideal, although others can also work with added drainage or nutrients. Feed clematis plants every 4 to 6 weeks during the growing season.
Prune your clematis at the correct time of year to promote good airflow. This reduces the risk of fungal infections like powdery mildew. Clematis are divided into three main pruning groups depending on when they flower.
It’s also worth noting that all parts of the clematis plant are considered poisonous, so it’s prudent to wear protective gloves when overseeing any care with these plants.
To get the most enjoyment from your clematis flowers, it’s vital to protect it against pests and diseases. Common clematis pests include aphids, scale insects, and spider mites. Clematis vines can also suffer from diseases such as wilt and powdery mildew. Horticultural oils, insecticidal soap, organic pesticides and fungicides can treat most problems.