My Yellow Bush Daisy Leaves Are Turning Black

Fungal Diseases

• Fungal diseases generally appear when the plant receives too much moisture, either in the form of heavy rainfall or from over-watering. Infections such as fusarium or phytophthora can spread from plant to plant by airborne spores, contaminated gardening tools or standing water at the base of the daisy plant. Infections often go unnoticed until leaves change color or spots appear on the foliage. Black spots may spread and merge as the disease progresses, discoloring the entire leaf. Check the roots, stems and foliage for signs of rot or fruiting bodies -- masses of spores. Take a sample of the blackened foliage to a cooperative extension service office to identify the fungus and get specific treatment instructions. Improve drainage around the plant, sanitize gardening tools between uses and prune diseased areas. Dispose of cuttings and other plant debris away from the plant to avoid spreading infection. Keep the area around the daisy free of weeds.

Insect Pests

• Aphids suck the juices from leaves and stems, interfering with the ability of the foliage to receive the moisture and nutrients sent up by the roots. Aphids and some other sucking insects leave behind a sticky substance known as honeydew that is a breeding ground for black mold. Examine the plant closely with a magnifying glass to look for insects or insect larvae infesting the plant. Treatment depends on the type of insect damaging the bush daisy and whether black mold is present. Try giving the foliage a hard spray from the garden hose to knock insects off the leaves. Treat heavy infestations with insecticidal soap or horticultural oil to smother insects and their larvae. Use a pesticide as a last resort, since several beneficial insects, like ladybugs and parasitic wasps, prey on bad bugs and may be killed by pesticides, thus making the infestation worse rather than better.

Leaf Scorch

• If the blackened foliage looks like the aftermath of a wildfire, the problem may be leaf scorch. Normally a problem of environment or culture, leaf scorch may occur if the plant receives too much fertilizer or is in full sunlight during unusually bright, hot weather. Try erecting a shade or filter to reduce the sun's glare. Mulch the plant to keep the roots cool and to retain moisture around the plant. Although African bush daisies are drought tolerant, if dry weather persists too long, provide the plant with supplemental water.

Preventing Disease

• Treat the Euryops pectinatus early in spring with protective fungicides. If insects are the problem, treat the plant with insecticides when the adults are in their most active cycle, before they have a chance to lay eggs. Improve soil drainage to prevent rots and discourage fungal spores. Prune away the blackened areas of foliage to give the plant a chance to produce new, healthy growth.