P&PDL Picture of the Week for
January 4, 2010

Root Rot of Potted Tulips

Tom Creswell, P&PDL Director, Plant Disease Diagnostician, Purdue University

We see few problems on tulips grown in pots for winter forcing, but growers occasionally encounter root rot problems with this crop. Symptoms on the foliage may include stunting, dead leaf tips, weak or distorted growth and yellowing. Healthy tulips at the bloom stage should show creamy white roots on the outside of the root ball but fungal pathogens can cause discoloration and decay.

Once the roots are heavily infected there is little that can be done to help plants recover. Prevention depends on starting with strong, healthy bulbs that have been properly conditioned for forcing and maintaining good sanitation throughout the growth stages. Commercial growers may also need to use fungicide drenches to help prevent the most common problems like Rhizoctonia root rot and Pythium root rot.

Click image to enlarge

Tulips

Potted tulips

Figures 1 & 2: Potted tulips showing symptoms of root decay problems.

Tulip tip dieback

Figure 3: Leaf tip dieback resulting from root rot.

Tulip root rot

Figure 4: Root rot caused by Pythium and Rhizoctonia.

Pythium spores

Figure 5: Spores of a Pythium species in root cells of tulip with root decay.

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service