The leaves and petals of my tulips are shot through with little holes. Is this some kind of insect or a disease? And what can I do to solve the problem?
Your tulips may have a fungal disease called Botrytis. According to Cornell University’s Plant Disease Diagnostic Clinic, Botrytis tulipae is specific to tulips and lilies. A more colorful name for this disease is ‘tulip fire.’ Cool and damp spring or summer conditions favor the development of the disease:
“Tulip fire infections cause malformations and/or large, light tan patches on tulip leaves. These patches are most noticeable on light-colored varieties. On leaves these infections are somewhat sunken, yellow to light tan, and surrounded by a water-soaked area.
On colored petals the spots appear white and on white petals they appear brown.”
Since the fungus can overwinter in plant debris, good garden hygiene may help:
- Clean up any diseased leaves and petals, but not when they are wet.
- Make sure you don’t water your tulips from above (of course, you can’t stop the rain–just don’t aid and abet it).
- Avoid congested plantings–provide air circulation around your plants.
- Ultimately, you may want to dispose of infected plants (don’t compost).
- Rumor has it that using a grit mulch around your tulips can be helpful as a preventive measure.
The Royal Horticultural Society advises that gardeners not plant tulips in a location where Botrytis has been present for three years. According to University of Illinois Integrated Pest Management, there is no point using fungicide where the fungus is already present, but they do describe preventive uses. Always look for the least toxic option. There are some Neem-based fungicides available for home gardeners.
An article in the Telegraph by garden writer Sarah Raven gives an excellent overview of the problem and how to manage it. She highly recommends not hesitating to remove infected plants and bulbs at first discovery, the better to keep the disease from spreading. Early tulips are less susceptible, and according to Raven, the most susceptible in her garden are Darwin tulips, while Viridiflora hybrids are unaffected. Avoid cross-contaminating lilies, fritillaries, and Juno irises by planting them at a distance from your tulips.