Last season, several growers in Northern Europe experienced problems with Ranunculus cultivation. These problems were of various natures. Schoneveld Breeding would like to try to tackle these problems together for the coming season, to successfully continue cultivation.
Below is an overview of the issues Schoneveld Breeding came across, and causes and advice based on Northern European circumstances:
Cause: Light deficiency, EC in the pot <0.5, crop treatments, plants are too wet for too long, inactive climate and choice of potting soil.
Advice: Keep the EC in the pot at a minimum of 0.8, use airy potting soil with at least 16-25% air, ensure sufficient air capacity, e.g. use fans.
Cause: Uneven young plant, EC in the pot >1.0 until plants are half-grown, pot clod too dry, bacteria, insects, stress-induced flowering caused by LD (longer than 11 hours) during the young plant phase (and up to 12 weeks after sowing) or due to clear full-moon nights during cultivation, stray light or plant stress caused by reducing the use of propiconazole too early.
Advice: Check young plants for pests and diseases, keep the clod sufficiently moist (moisture level 3), use a screen at 200 Watts for major weather transitions from dark to light and a closed screen at full moon, do not use propiconazole until half-grown.
Cause: Caused by LD (longer than 11 hours) during the young plant phase (up to 12 weeks after sowing), by clear full moon nights during cultivation or reducing the use of Tilt too early, stress in the plant due to high light intensity, stray light, dry clod or EC >1.0 in the clod.
Advice: use a screen at 200 Watts for major weather transitions from dark to light and close the screen at full moon, do not use Tilt until half-grown, keep the clod sufficiently moist (moisture level 3), EC clod <1.0
Cause: Emerges under humid warm conditions or contaminated water.
Advice: Make sure the crop is dry in the evening after irrigation or crop treatment. Use clean water. Irrigate or use drippers as soon as the roots stick out of the clod.
Cause: Humid warm conditions during cultivation.
Advice: Check the source material, preventative spraying with Mepanipyrim, Fluopyram, Boscalid + Kresoxim-methyl or vaporize sulphur.
Yellow leaves caused by crop treatment
Cause: Growth inhibitor with too high concentrations of daminozide 85% (>250g/100 litres of water) and/or additives, use of insecticides / fungicides under extreme climatic conditions.
Advice: Close the screen > 200 Watt, if using growth inhibitors use a low concentration more often. Do not use iprodion, spiromesifen or metalaxyl-M.
Pythium / Phythophthora
Cause: Created by an incorrect choice of potting soil or uneven irrigation/fertilisation or infection pressure.
Advice: Potting soil must have good drainage capacity with sufficient air, 16-25%, use disinfected water, the crop can be treated preventively as a precaution.
Cause: Insufficient crop monitoring.
Advice: Regular crop monitoring. Keep doors closed and avoid draughty corners.
Cause: Is not the cause but the result, plants are wet for too long and/or choice of potting soil.
Advice: Ensure sufficient air movement in the greenhouse, use airy potting soil with at least 16-25% air, ensure a dry top layer of the potting soil.
Cause: Too much daminozide (>250 g/100 litres of water) under very low light and cold cultivation conditions.
Advice: Start as soon as the plant is well rooted and it is better to use a low concentration more often.