Bulb, Crown and Root Rot (fungi – Penicillium spp., Sclerotium rolfsii, Pythium spp., Fusarium spp., Rhizopus stolonifer, Rhizoctonia solani, Aspergillus spp.): Tulips may not come up or leaves may be yellow or reddish, stunted, and die because the bulb is rotted. Root may be slimy, soft, dry, hard or powdery in texture. Color may be dark or light gray, black or brown with moldy growth on bulb or scales. Remove and destroy infected plants. Avoid bruising in handling bulbs. Plant clean disease-free bulbs. Water and fertilize properly.
Botrytis Blight (fungus – Botrytis cinerea): Leaves and petals are affected with a brown decay, which often destroys large areas. Buds are sometimes blighted, or the flower stalks may tip over from a spot on the side where the fungus has attacked. A brownish-gray, powdery mold is produced on the surface of affected parts. All affected parts should be gathered and burned as soon as possible. Badly affected bulbs should be destroyed. Tulips should not be planted the next year in soil where this disease has been abundant. Plant grown in the greenhouse should be kept well ventilated.
Virus Diseases (Tulip breaking, Mosaic): Flowers may show changes in color with breaking, streaking, greening or darkening. Leaves and flower stems are mottled or streaked with light green or yellow areas. Plants are stunted and have poor vigor. Viruses are spread by cutting flowers and by several species of aphids. Destroy diseased plants when found. Control insects and weeds.