What can go wrong with bulbs?

Spring and summer bulbs are great additions to the garden, but sometimes, they, too, can succumb to pests and diseases. Here is a chart outlining a few signs and symptoms, and troubleshooting tips to nurse your plants back to health.

Signs and symptoms: stems, leaves, or flower buds are covered with small green or black insects; growth is often malformed.

Cause: aphids (greenflies or blackflies).

Control: spray plants with a strong stream of water; if flower buds are present, spray with insecticidal soap.

Signs and symptoms: rust-coloured streaks on leaves and flowers, especially those of potted narcissi. Leaves and flowers stunted.

Cause: bulb scales or bulb mites.

Control: destroy severely infested bulbs.

Signs and symptoms: flowers and foliage of gladioli have silvery streaks and patches, which eventually turn brown.

Cause: thrips.

Control: destroy infested flowers and foliage. Spray affected plants early with Beauveria bassiana. Insecticidal soap and neem may be effective.

Signs and symptoms: plants are stunted, foliage is normal in colour but small. Flowers fail to open normally or open and droop.

Cause: shallow planting (especially tulips).

Control: When foliage starts to turn yellow, lift bulbs and either store until next fall or replant at proper depth.

Signs and symptoms: anemone leaves have patches of whitish powder.

Cause: downy mildew (fungus).

Control: spray with baking soda.

Signs and symptoms: leaves of gladioli turn yellow and topple over, usually before flowers appear. Corms show black spots or lesions; later, corm shrivels.

Cause: dry rot (fungus).

Control: remove and destroy infected plants; dust remaining bulbs with sulphur before storing. Replant in new location.

Signs and symptoms: foliage of tulips shows water-soaked specks and streaks, which turn brown. Petals are often spotted. Brown rot may attack stems, which topple over.

Cause: tulip fire, or botrytis (fungus).

Control: destroy diseased plants. Dust remaining bulbs with sulphur. Replant in another location.