Plant Health Problems
See Bulbs for a detailed discussion of problems that may occur and are common to most bulbs.
Diseases caused by Fungi:
Fire or Botrytis blight, Botrytis tulipae.
This is the most common problem of tulips. Leaves are flecked with small brown spots. As the spots enlarge or become more numerous, large brown patches can develop. Flowers are also frequently flecked with brown to tan spots. Under conditions of high humidity, these spots are accompanied by the brown-gray mold of the fungus. Infection can also lead to the collapse of leaves, stems, and flowers.
Control involves cutting and removing any affected plant parts. It is also helpful to avoid overhead irrigation and crowding of the plants. When conditions are favorable, applications of fungicides can be made when new growth emerges in the spring. Among the compounds registered for use in Connecticut are chlorothalonil, thiophanate-methyl, iprodione, and mancozeb. Consult the label for dosage rates and safety precautions.
Diseases caused by Bacteria:
Soft rot, Erwinia carotovora.
Infected plants fail to flower or blossoms fall off before they open. Tops may appear water-soaked and collapse. Infected bulbs have a strong odor and are soft and mushy.
Since this pathogen is highly contagious, all infected bulbs should be discarded. It is helpful to carefully remove any symptomatic foliage and plant debris in the fall after the tops have been killed by frost. Bulbs should be planted in well-drained soil and watered early in the day. This disease can also be minimized by avoiding overcrowding and wounding during cultivation. Sanitation is also very important. All equipment should be disinfested between use with 10% household bleach, 70% alcohol, or one of the commercially available compounds. It is also helpful to control insects and mites since injuries associated with their activity provide sites for infection.
Diseases caused by Viruses:
Symptoms of infection include stripes or streaks of white or another color in the normal colored petals. Leaves of virus-infected plants may appear distinctly mottled. The disease is persistent in the bulbs and the virus is transmitted from plant to plant by aphids, especially in situations where plants are crowded and heavily infested.
It is very helpful to rogue and destroy infected plants and bulbs since this helps to minimize spread of the virus. Control of the aphid vectors is also important.
Diseases caused by Physiological/Environmental Factors:
Return bloom, physiological.
Many gardeners experience problems with lack of return bloom with tulips after the first year. The cause for this is unknown but may be associated with weather and other factors that affect the physiology of the bulb.
If return blooms are important, new bulbs should be planted each year. In other cases, tulips can be considered as an annual or a short-lived perennial.
Flower stalks collapse for no apparent reason or visible injury. Topple has also been reported on iris and gladiolus. This problem has been associated with calcium deficiencies.
This disease can be minimized by careful attention to nutrition and watering.