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Lily (Lilium spp.)-Root Rots

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Latest revision: 
March 2024

Rotted roots due to Pythium sp.

OSU Plant Clinic image, 2015.

Underground symptoms include rotted portions on roots and bulbs. These lesions had Cylindrocarpon, Rhizoctonia and Trichoderma.

OSU Plant Clinic, 2020.

See:

Greenhouse Plants, Ornamental - Pythium Seed Rot, Damping-off, and Root Rot

Lily (Lilium spp.) - Basal Rot (Bulb Rot)

Lily (Lilium spp.) - Nematode, Root-lesion

Cause The fungi Fusarium oxysporum, F. tricinctum, Trichoderma spp., Thanatephorus cucumeris AG 2-1 (Rhizoctonia solani) and Rhizoctonia spp. (Ceratobasidium sp. AG-I and AG-K isolates) isolated from PNW grown bulbs were found to cause a necrosis and root rot when inoculated individually onto potted plants. Symptom development was more rapid with prior exposure to root lesion nematodes. Root rots caused by Pythium ultimum, Cylindrocarpon sp., Fusarium oxysporum, and Rhizoctonia solani are the major disease problems during the forcing of lilies. P. irregulare has been found more frequently in the Northeastern United States. These pathogens often form a root rot complex together. Fusarium bulb rots are more common during the winter when soils can be excessively wet, and Pythium root rot is more common under warm, moist conditions.

Symptoms General symptoms associated with root rot consist of a general loss of quality, stunted growth, and the premature yellowing and senescence of lower leaves on the plants. Underground symptoms include rotted portions on roots and bulbs. Root rots can also lead to an increase in the postharvest senescence of leaves, especially when plants are placed in cold storage prior to shipping.

Cultural control

  • Use healthy planting stock.
  • Plant only in well-aerated, well-drained, pathogen-free media. Also disinfect any tools and equipment that might be used with and contaminate the media.
  • Avoid reusing pots or trays from a previous crop for propagation. If pots must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.
  • Destroy bulbs with lesions or rots at base of scales.
  • Propagate from rot-free scales.
  • Improve soil drainage.
  • Use low-nitrogen fertilizers.
  • Remove remnants of bulbs and plant debris.

Chemical control Preventive chemical soaks or drenches are commonly used to limit the damage caused by root rot pathogens.

  • 42-S Thiram at 1.5 pints/8 gal water. Agitate suspension before soaking bulbs. See label for details. Group M3 fungicide. 24 hr reentry.
  • Captan 4L Fungicide at 1 gal/100 gal solution. Soak bulbs for a minimum of 15 min. before planting. Do not use alone. Solution may be disposed of in the planting beds at a maximum rate of 100 gal/A. Oregon only SLN-180002. Group M4 fungicide. 48-hr reentry.
  • Postiva at 10 to 28 fl oz/100 gal water as a pot drench. Group 3 + 7 fungicide. 12-hr reentry.
  • ProStar 70 WG at 3 to 6 oz/100 gal water. Soak clean bulbs for 5 min. and allow to dry prior to planting. For Rhizoctonia root rot. Group 7 fungicide. 12-hr reentry.
  • Terraclor 400 at 6 to 9 pints/100 gal water. Before soaking, hose or dip bulbs in water to remove soil, which would reduce the soak's effectiveness. Soak bulbs for 5 to 15min. Add 1% sticker and maintain good agitation. Group 14 fungicide. 12-hr reentry.
  • Vitavax 34 at 1.5 to 3 quarts/100 gal water. Soak bulbs at least 5 to 15 min. For Rhizoctonia root rot. Group 7 fungicide. 12-hr reentry.

For Pythium only:

  • Apron XL at 0.085 to 0.64 fl oz/100 lb "seed". Will control Pythium, but not Rhizoctonia. Group 4 fungicide.
  • Banol at 2 to 3 fl oz/10 gal water. Group 28 fungicide. 12-hr reentry.
  • Fosphite at 1 to 2 quarts/100 gal water. Do not use copper products within 20 days of treatment and do not use spray adjuvants. Group P7 fungicide. 4-hr reentry.
  • Mefenoxam 2 AQ at 0.49 fl oz/100 gal water as a soil drench at planting. Use only once. Resistant isolates have been detected in the Northeastern United States. Group 4 fungicide. No restrictions on reentry when used as a soil drench or media incorporation.
  • MetaStar 2E at 1 fl oz/100 gal water once at planting only. Group 4 fungicide. 48-hr reentry.
  • Proplant at 2 to 3 fl oz/10 gal water. Group 28 fungicide. 12-hr reentry.
  • Subdue MAXX at 1 fl oz/1,000 sq ft, irrigated in with 0.5 inch water. Resistant isolates have been detected in the Northeastern United States. Group 4 fungicide. No restrictions on reentry when used as a soil drench.

Biological control Use in conjunction with other control tactics such as thorough sanitation.

  • Actinovate AG (Streptomyces lydicus strain WYEC 108) at 3 to 12 oz/A is registered for Fusarium. 4-hr reentry. O

References Chastagner, G.A., van Tuyl, J.M., Verbeek, M., Miller, W.B., and Westerdahl, B.B. 2018. Diseases of Lily. In McGovern, R.J. and Elmer, W.H. (eds.) Handbook of Florists' Crops Diseases. Springer Int.

Lakshman, D., Vieira, P., Pandey, R., Slovin, J., and Kamo, K. 2017. Symptom development in response to combined infection of in vitro-grown Lilium longiflorum with Pratylenchus penetrans and soilborne fungi collected from diseased roots of field-grown lilies. Plant Disease 101:882-889.

Lakshman, D.K., and Kamo, K. 2018. First report of lily root rot caused by Thanatephorus cucumeris AG 2-1 in the United States. Plant Disease 102:819-820.