9 Common Wildflower Pests and Diseases (and How to Deal With Them)

Wildflowers create beautiful and colorful summer displays in our gardens. However, wildflowers are vulnerable to pests and diseases like aphids and powdery mildew. In this article, we’ll discuss nine common wildflower pests and diseases and how to combat them.

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Common Wildflower Pests and Diseases

1) Aster Yellows

Aster yellows are a common wildflower disease transmitted by leafhopper insects. The condition is caused by a phytoplasma that lives on leafhoppers and moves to plants.

Infected plants display misshapen flowers covered in strange green growths. Infected plants may also have yellowing leaves with green veins.

Wildflowers infected with aster yellows won’t recover. Remove any infected plants and clear fallen leaves and weeds away from surviving wildflowers. Eliminate leafhoppers using insecticidal soap or horticultural oils.

2) Botrytis Blight

Also known as gray mold, botrytis blight is a fungal disease that infects wildflowers. Botrytis blight causes gray mold to appear on infected plants. Other symptoms include large brown spots on flowers or flower buds turning black.

Botrytis blight thrives in humid environments, so avoid overwatering your wildflowers. Keep space between your wildflowers to improve air circulation. Botrytis blight targets wounds in flower stems, so avoid damaging your wildflowers when cutting them back.

3) Powdery Mildew

Powdery mildew is a fungal disease known to most gardeners. Powdery mildew thrives in humid conditions and cooler temperatures. Infected wildflowers have powdery white stains on the leaves. Other symptoms include curled or discolored leaves.

Give your wildflowers enough space to promote good air circulation and avoid overwatering. Remove any leaves that show signs of powdery mildew. Remove any fallen leaves around your wildflowers, as powdery mildew survives on leaf debris during the winter.

4) Root Rot

Root rot is a common issue caused by overwatering. Most wildflowers need loose, well-draining mediums to prevent waterlogged soil. Symptoms of root rot include drooping or yellowing leaves and stunted growth.

Check the roots and remove any brown, mushy, or smelly ones. Make sure the soil drains well by mixing in some sand or grit. Established wildflowers don’t need watering unless struggling in extended periods of drought. Stop watering to reduce the risk of root rot.

5) Stem Rot

Stem rot is another fungal disease that can attack wildflowers. It’s caused by various types of fungi within the soil. Symptoms include wilting leaves, stunted growth, and spots on the stems.

Remove all fallen leaves and other debris around your wildflowers. Stem rot can survive for five years in the soil, so fungicides are often the easiest option. Discard infected plants safely. Avoid overwatering your wildflowers, as stem rot thrives in humid, waterlogged conditions.

6) Aphids

Aphids are small sap-sucking insects that can decimate wildflowers. Aphids are often green or black, and huddle along stems or underneath leaves in large groups. Other symptoms of an aphid infestation include distorted or stunted growth and black mold.

Evict aphids by blasting plants with a hose. You can also use insecticidal soap or horticultural oils to eliminate aphids. Avoid synthetic pesticides wherever possible, as these can also kill beneficial insects like bees.

7) Plant Bugs

Plant bugs are a diverse group of pests that target wildflowers like cosmos. They consume sap and leave behind bite marks on the leaves. Plant bugs come in various colors and patterns and can also fly from plant to plant.

Spraying your wildflowers with a hose should get rid of plant bugs. If the infestation persists, use horticultural oils or insecticidal soap. These products dry out pests like plant bugs and interrupt their breeding cycles.

8) Scale Insects

Scale insects are another sap-sucking pest that feeds on wildflowers. Scale insects have waxy armored shells and excrete sticky honeydew onto leaves. This honeydew can turn into deposits of black mold. You may also find clutches of white eggs underneath leaves.

Eliminate scale insects using horticultural oils or insecticidal soap. If the infestation is too large, organic pesticides should destroy the insects. Synthetic pesticides can kill scale insects but will also harm bees and other pollinating insects.

9) Spider Mites

Spider mites are tiny insects that consume chlorophyll – the green pigment in a plant’s leaves. As such, spider mites can cause stunted or distorted growth. Other symptoms include white webbing around the leaves and brown or yellow leaf spots.

Horticultural oils or insecticidal soap are the best ways to get rid of spider mite infestations. You could also use biological control measures such as predatory mites. Many wildflowers can tolerate small spider mite infestations.

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Common Wildflower Pests and Diseases: Wrapping Up

Wildflowers are vulnerable to pests and diseases like aphids and spider mites, along with diseases like aster yellows. Treat most issues using horticultural oils or insecticidal soap. If you do need to use pesticides, use organic ones wherever possible. Synthetic pesticides can kill beneficial insects like bees as well as pests.

For more, see our in-depth guide on how to plant wildflowers in your garden.

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