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Upper Leaf Necrosis in Oriental Hybrid Lilies William B. Miller and Y.-C. (Alex) Chang

Upper Leaf Necrosis in Oriental Hybrid Lilies William B. Miller and Y.-C. (Alex) Chang Department of Horticulture Cornell University. How do ULN symptoms develop?. 1st day symptoms visible. 21 days later. When does ULN occur?. % Necrosed Plants.

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Upper Leaf Necrosis in Oriental Hybrid Lilies William B. Miller and Y.-C. (Alex) Chang

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

  2. .

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

  4. When does ULN occur? % Necrosed Plants Most plants begin to show symptoms 30-40 days after planting

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

  6. Tissue analysis Tissue taken at this ULN stage

  7. 1 2 3 4 5

  8. 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

  9. Calcium • 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)

  10. Bulb Scales

  11. All Leaves

  12. Folded (young) Leaves

  13. Sand cultures…14/16 cm bulbs 0 mM Ca 0.2 mM Ca 4 mM Ca

  14. Ca-free nutrient solution reproduced ULN symptoms

  15. Larger bulb sizes increase ULN

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

  17. Artificial Leaf Unfolding

  18. Artificial Leaf Unfolding Control 1X/day 2X/day

  19. Overhead fans to blowing down

  20. Overhead fans to reduce ULN Fan off Fan-low Fan-high

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

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

  23. Conclusions • 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 30-40 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

  24. Conclusions • Factors that increase ULN: • Larger bulbs • Low transpiration • High humidity (mist) • 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

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

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