picture of the week
February 24, 2020
Easter Lily Production "Blues"
Janna Beckerman, Ph.D., Professor & Plant Pathology Extension Specialist, Purdue University
Easter lilies have the potential for developing root rot during vernalization and greenhouse production. Lily growers can avoid this problem, along with lower leaf yellowing and flower abortion by the management practices they implement now.
It is important to routinely remove plants from their pots and visually inspect the roots. The roots should have white root tips (Figure 1); any browning is likely a root rot pathogen. Preventive fungicides should be used on a regular schedule (every four to six weeks) to prevent Pythium, Phytophthora, Fusarium and Rhizoctonia spp., especially late in the crop cycle. It is important to rotate between chemical classes to prevent fungicide resistance. The following fungicide drenches are recommended (Always consult labels carefully for exact rates and to see if the material is registered in your state):
|Banrot||1+14||8 oz/ 100 gal water|
|Clearys 3336||1||8 oz/ 100 gal water|
|Chipco 26019||2||Refer to label|
|Empress Intrinsic||11||2-6 oz/100 gal water|
|Heritage||11||0.2-1 oz/100 gal water|
|Pageant Intrinsic||11+7||12-18 oz/100 gal of water|
|Subdue MAXX||4||½ oz/ 100 gal water|
|Truban 30 WP||14||3 to 10 oz/ 100 gal water|
When drenching bulbs, use enough solution to wet the root zone of the plant. Be sure to thoroughly cover and wet the crown, base of the plant, and surrounding growth media for best control. Avoid watering plants for several hours before application in order to improve plant uptake of the fungicide.
Lowering leaf yellowing and leaf drop is commonly observed from visible bud to flowering in a tightly spaced crop or one that has been heavily treated with growth regulators (Figure 2). An early-season application of Fascination or Fresco [gibberelins (GA4+7) and cytokinin (Benzyladenine 6BA)] 1 week before and 1 week after visible bud to the lower leaves will prevent lower leaf yellowing. Do not apply to the upper leaves as stem elongation can occur. A late-season application to the foliage and buds is recommended when the largest bud is 8 cm in length to reduce lower leaf yellowing and prolong post harvest life. Plants treated with either Fascination or Fresco maintain green lower leaves (Figure 3). The following table has suggested rates of Fascination and Fresco (again, carefully consult the label):
Table 2. Time from visible buds to first open flower at various average daily temperature
|Application||Rate (6BA/GA4+7)||Ml or (oz) of Fascination or Fresco per 1 gal. water|
|Early-season||10/10 ppm||2.1 ml (0.07 oz)|
|Late-season||100/100 ppm||21 ml (0.71 oz)|
Remember that forcing temperatures above 75 °F can lead to flower bud abortion in Easter lilies (Figure 4). The rate of plant development from visible bud to flowering is only linear between 57° and 72 °F. For example, increasing the average daily temperature from 55 °F to 60 °F decreases time to flower by 4 days (Table 3). An increase in temperature from 80 °F to 85 °F results in only a one-day decrease in time to flower. Table 3 shows the predicted time from visible bud to flower at average daily temperatures ranging from 55 °F to 85 °F.
|Average daily temperature (°F)||Days from visible bud to flower|
This article was updated from a previous article (2008) written with Roberto G. Lopez, Ph.D.