Pests and Diseases of Garden Flowers

Pests and Diseases of Garden Flowers

Aphids (various species)

Lupin aphid (Macrosiphon albifrons) on Lupin (Lupinus sp.)

Young shoots and blooms of most plants can become infested with different aphid species. The large lupin aphid on lupins and black bean aphid on nasturtiums can be particularly damaging. However, most herbaceous plants grow vigorously enough to overcome attacks.

Typical symptoms: Leaves and shoots become infested with tiny insects of varying colours. Leaves may be blistered, distorted, sticky and blackened; shoot may be distorted. Symptoms may persist when the pests have flown.

Prevention and treatment: See Aphids as Garden Pests

Caterpillars (various species)

Typical symptoms: Irregular holes are eaten in leaves. Caterpillars may or may not be seen. Check at night to confirm that the damage is not caused by slugs or earwigs.

Prevention and treatment: Examine plants regularly and remove caterpillars. If this is not practical, spray pests with derris.


Earwigs attack ornamental plants, especially chrysanthemums clematis, dahlias, delphiniums and pansies.

Typical symptoms: Ragged holes are eaten in the flower petals.

Prevention and treatment: See Organic Gardening – Benefits of Garden Insects and Garden Pests and Diseases – Barriers and Traps

Leaf miners (various species)

Leaf miners attack chrysanthemums and calendula; also other plants.

Typical symptoms: Silvery snaking “mines” appear in the leaves.

Prevention and treatment: Pick off affected leaves or squash the larvae within the leaves. Weed out groundsel and sow thistles, which can harbour the pests.

Lily beetle (Lilioceras Mit)

This pest attacks lilies and fritillaries.

Typical symptoms: Bright red beetles and their plump red and black larvae eat the foliage in late spring. Beetles and larvae can cause considerable damage if conditions are favourable.

Prevention and treatment: Check lilies regularly in spring and remove any beetles and larvae that are found. Spray pests with derris.

Powdery mildew (various species)

Powdery mildew is found on asters, calendula, chrysanthemums, forget-me-nots, lupins, sweet peas, violas and other plants.

Typical symptoms: A white powdery coating appears on leaves and stems.

Prevention and treatment: See How to Treat Common Plant Diseases

Rusts (various species)

Rust affects antirrhinums, cornflowers, sweet Williams, hollyhocks; also other types of ornamental plants.

Typical symptoms: Leaves are infected with yellow, rusty or brown pustules.

Prevention and treatment: Grow resistant varieties of antirrhinum. If hollyhock rust is a recurring problem, treat hollyhocks as biennial rather than perennial plants. Do not overfeed sweet Williams with nitrogen. Remove diseased plant material; herbaceous plants that get rust every season should be removed, as the disease will be living within the plant.

Slugs and snails

Typical symptoms: Irregular holes are eaten in the foliage of bedding and herbaceous plants, especially during wet weather in spring and autumn. Slime trails are visible.

Prevention and treatment: See Slugs and Snails – Garden Pest Control

Solomon’s seal sawfly (Phymatocera aterrima)

This pest affects Solomon’s seal only.

Typical symptoms: The foliage of affected plants is shredded; greyish-white caterpillars with black heads are found on the plants.

Prevention and treatment: Regularly check all flowering plants as this is when the sawfly lays its eggs. Remove and destroy any eggs and caterpillars.

Virus, cucumber mosaic

Cucumber mosaic virus affects many ornamental plants, anemones, aquilegias, begonias, campanula, dahlias, lilies and primulas being particularly susceptible.

Typical symptoms: Affected plants show irregular yellow mosaic or mottling of leaves; distorting of leaves and flowers and stunted growth.

Prevention and treatment: See Garden Pests and Diseases of Cucurbits

Viruses, other

Other viruses affect chrysanthemums, sweet peas (pea viruses), nicotianas and petunias (potato viruses).

Typical symptoms: Leaves are distorted and/or mottled and flowers are distorted and/or streaked.

Prevention and treatment: See Plant Diseases – Understanding the Problem

Wilt (various species)

Antirrhinums, asters, begonias, chrysanthemums, delphiniums, sweet peas and wallflowers are susceptible to wilt.

Typical symptoms: Plants wilt; at first they may recover overnight.

Prevention and treatment: See How to Treat Common Plant Diseases

02. February 2011 by Dave Pinkney
Categories: Organic Gardening, Pests and Diseases, Plant Care | Tags: , | Comments Off on Pests and Diseases of Garden Flowers


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