Upper Leaf Necrosis in Oriental Hybrid Lilies William B. Miller and Y.-C. (Alex) Chang Department of Horticulture Cornell University

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How do ULN symptoms develop? 1st day symptoms visible 21 days later

When does ULN occur? Most plants begin to show symptoms days after planting % Necrosed Plants

Where do ULN symptoms occur? ULN only occurs on leaves associated with flower buds and the leaves immediately below the buds

Tissue analysis Tissue taken at this ULN stage

The hypothesized cause of ULN ULN is a calcium deficiency disorder:   Leaf overlap reduces transpiration, thereby reducing Ca transport to the young leaves, thereby encouraging the symptoms   Also due to insufficient Ca supply from the bulb

Calcium Calcium moves upward in plants with the water flow Calcium moves upward in plants with the water flow  Xylem (water-conducting) system  Calcium accumulates in leaves that are actively losing water through transpiration  Young or “congested” leaves don’t transpire as much  Leaves (or fruit) that grow faster than their calcium supply are susceptible to calcium deficiency problems (e.g. blossom end rot in tomato)

Bulb Scales

All Leaves

Folded (young) Leaves

0 mM Ca0.2 mM Ca4 mM Ca Sand cultures…14/16 cm bulbs

Ca-free nutrient solution reproduced ULN symptoms

Larger bulb sizes increase ULN

12/14 cm16/18 cm14/16 cm Bulb size vs. leaf enclosure ( “ apical congestion ” )

Artificial Leaf Unfolding

1X/dayControl2X/day

Overhead fans to blowing down

Overhead fans to reduce ULN Fan offFan-lowFan-high

Adding calcium to bulbs before planting A range of studies, using several Ca concentrations and dipping times (1 min to 16 hours) were conducted A range of studies, using several Ca concentrations and dipping times (1 min to 16 hours) were conducted Basic conclusion: no positive effect Basic conclusion: no positive effect

Effectiveness of bulb dips in calcium chloride on upper leaf necrosis on Lilium cv. Star Gazer.

Upper Leaf Necrosis is a calcium deficiency disorder: Upper Leaf Necrosis is a calcium deficiency disorder:  Insufficient Ca supply from the bulb  Insufficient transpiration resulting from leaf enclosure of the shoot apex  Necrosis symptoms begin to show days after planting  This is when plants are about 12” tall  The 5 leaves immediately below the flower buds and the leaves associated with the buds are most susceptible to ULN Actual injury occurs much earlier than symptom expression Actual injury occurs much earlier than symptom expression Conclusions

Factors that increase ULN: Factors that increase ULN:  Larger bulbs  Low transpiration  High humidity (mist) Horticultural methods to reduce ULN: Horticultural methods to reduce ULN:  Use smaller bulbs if applicable  Keep greenhouse “dry”  Prevent water accumulation on leaves  Supplemental lighting in winter  Daily foliar Ca sprays (days 25-45)  Bulb dips are not promising  Airflow! Overhead fans offer a promising method to control ULN Conclusions

Acknowledgements USDA/ARS-SAF National Floriculture Research Initiative USDA/ARS-SAF National Floriculture Research Initiative Fred C. Gloeckner Foundation Fred C. Gloeckner Foundation Royal Dutch Wholesalers Association for Flowerbulbs and Nursery Stock Royal Dutch Wholesalers Association for Flowerbulbs and Nursery Stock Post/Schenkel Memorial Council Post/Schenkel Memorial Council Ministry of Education, Taiwan Ministry of Education, Taiwan