Phytotoxicity and Efficacy of Florel (Ethephon) for Growth Control of

Flamenettle (Coleus sp. cv. “B”)

By

Heiner Lieth, Director Linda Dodge Shannon Still

Ron Lane

Project: USDA Interregional Research Project #4 Project Number 13526A – May 14, 2003

Acknowledgements: Donors/Supporters: CDFA Minor Crops Research Grant, Project 2: Enhancement of the Western

Region IR-4 Program to Address California Needs

UC Davis Environmental Horticulture IR4 Center Department of Environmental Horticulture University of California One Shields Ave. Davis, CA 95616 http://envhort.ucdavis.edu/ir4

PR.NO.: 13526A TRIAL: 2 DATE: 5/14/03

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IR-4 ORNAMENTAL DATA REPORTING FORM 1. INVESTIGATOR (Name, Address, Phone#):

Dr. Heiner Lieth Department of Environmental Horticulture University of California One Shields Ave. Davis, CA 95616 Ph 530-752-7198 FAX 530-752-1819 Email: jhlieth@ucdavis.edu

LOCATION OF TRIAL: Dept. of Env. Hort., University of California, Davis TRIAL TYPE field (lath house), container

2. PESTICIDE:

COMMON NAME: Ethephon FORMULATION: 3.9% ai BATCH NO.: PRODUCT: Florel EPA REG. NO.: 54705-8 MFG: Monterey Chemical

3. USE INFORMATION: COMMON NAME SCIENTIFIC NAME

PLANT: Coleus, Flamenettle Coleus cv. “B” REASON: Control of vegetative growth SOIL TYPE OR TYPE OF POTTING MIX: UC Mix

% SAND 15 % PERLITE 50 % OM 35 pH 6.5 CUTTING DATE: 04/18/03 TRANSPLANTING DATE: 05/01/03 PLANT OR POT SPACING 6 inches ROW SPACING 6 inches POT SIZE 6-INCH PLOT SIZE 25 sq ft EXPERIMENTAL DESIGN completely randomized NO.OF REPS 4

4. APPLICATION PARAMETERS:

TYPE OF APPLICATION foliar spray NO. OF APPLICATIONS one APPLICATION TYPE quart-size spray bottle NOZZLE TYPE/SIZE NOZZLE PRESSURE DELIVERY RATE CALIBRATION DATE(S)

5. APPLICATION SUMMARY:

APPL.DATE

RATES (a.i./A)*

GROWTH STAGE

5/14/03

0, 0.32, 1.6, 3.2, 6.4 fl. oz./gal (0, 100, 500, 1000, 2000 ppm)

Transplanted cuttings

*Be sure to provide units

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IR-4 ORNAMENTAL DATA REPORTING FORM (Please type or print) 6. RAINFALL/IRRIGATION RECORDS:

INCLUDE RAINFALL/IRRIGATION INFORMATION (printouts, IR-4 forms, etc.) Plants were irrigated as needed with ½ strength Hoagland’s solution

7. OTHER PESTICIDES, FERTILIZER, LIME AND ADJUVANTS USED: None 8. NARRATIVE SUMMARY OF METHODS AND RESULTS: (Use more pages if needed)

Materials and Methods Plant Material and Culture. Coleus cv. “B” is a medium to large upright variety having lanceolate leaves with crenate margins. The leaf color pattern consists of random chimeric patches of pink, burgundy and green. Stem cuttings with two nodes were taken from Coleus cv. “B” plants growing in the Environmental Horticulture greenhouse. The cuttings were stuck on 04/18/03 using a medium of 50% UC Mix and 50% perlite and placed in a mist bench with bottom heat of 75°F for two weeks (Figure 1). The rooted cuttings were transplanted on 05/01/03 to six-inch pots (one cutting per pot) with a medium of 50% UC Mix and 50% perlite and grown on in a glasshouse for two weeks. On 05/13/03, the coleus plants were transferred to an outdoor lath house. During the course of the experiment (05/14/03 to 06/17/03) the plants were watered as needed with ½ strength Hoagland’s solution. The plants were grown under natural daylength and at temperatures averaging 86°F (maximum) and 54°F (minimum). Environmental conditions during the experiment are summarized in Table 1. Experimental Procedure. Twenty 6-inch plants were randomly chosen and individually tagged for treatment with 0, 100, 500, 1000 or 2000 ppm ethephon (0, 0.2x, 1x, 2x or 4x recommended rate) with 4 replicates per treatment. The plants received one foliar spray application of the designated treatment on 05/14/03. Plant leaves and stems were sprayed to runoff using quart-sized manual spray bottles. The plants were arranged in a completely randomized design on 05/16/03 (Figure 2). The plants were not pinched. Phytotoxicity observations using a numerical rating scale of 0 (no injury) to 10 (complete kill) were made weekly until 6/17/03 (four weeks). Measurements of plant height (cm) and diameter (cm) were made weekly until 6/17/03 (four weeks). Plant height was determined as the visual average of the branches in a pot measured from the soil level to the terminal growing points (not including any inflorescences). Plant diameter was determined as the average of two diameter measurements (between stem tips) made perpendicular to each other at the top of the plant. Statistical Analysis. The data were analyzed using Proc GLM of the Statistical Analysis System (SAS). Phyotoxicity data were analyzed using t-tests. The mean increases from the starting height and width were analyzed for significant differences using t-tests. Where differences were not evident between treatments, the data were grouped into “low” dosage (control and 0.2x) and 1x, 2x, and 4x, and analyzed for differences between the measurement at start and that at week 1, 2, 3, and 4, to determine if further study is warranted. Results Phytotoxicity. Some leaves of Coleus cv. “B” plants appearing after foliar application of ethephon showed slight cupping and distortion (Figure 3). Plants with these leaves were given a phytotoxicity rating of “1”. Ratings varied during the course of the experiment but by week 4 the controls had an average rating of “0”, plants treated with 100 ppm or 500 ppm ethephon had an average rating of “0.5” and those treated with 1000 ppm or 2000 ppm ethephon averaged a rating of “1” (Figure 4, Appendix A). None of these plants showed a degree of phytotoxicity that would deem them unmarketable. Control of Plant Growth. Four weeks after one foliar application of 0, 100 ppm, 500 ppm, 1000 ppm or 2000 ppm ethephon (0, 0.2x, 1x, 2x or 4x recommended rate), Coleus cv. “B” plants showed differences in flowering and internode length (Figures 5 and 6). The number of inflorescences per plant was reduced significantly for the plants treated with 1000 ppm (2x) or 2000 ppm (4x) ethephon, averaging less than two per plant (Figure 5). Plants in the

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other treatment groups averaged 5-6 inflorescences per plant. Internode length averaged near 8 cm for the control plants and for those treated with 100 ppm (0.2x) ethephon (Figure 5). Internode length for plants treated with 500 ppm (1x) or 1000 ppm ethephon (2x) was reduced significantly to around 6 cm. Internode length for plants treated with 2000 ppm (4x) ethephon was further reduced significantly to less than 4 cm, half that of the controls. The number of branches per plant was not significantly different among the treatments (Figure 5). Increases in plant height over the course of the experiment were significantly reduced for the 2000 ppm (4x) treated plants during weeks one and two (Figure 7, Appendix B). At the end of the experiment, there were no significant differences in plant height increase among the treatments (Figure 7, Appendix B). Increases in plant diameter were not significantly different among the treatments over the course of the experiment (Figure 8, Appendix C). For Coleus cv. “B”, ethephon appeared to delay flower initiation. New growth on plants receiving the higher treatment rates was vegetative while the control and lower treatment rate plants produced inflorescences earlier. While the ethephon treatments reduced internode length, the plants in these treatments still grew as tall as the control plants due to the production of additional nodes and internodes. The 100 ppm (0.2x) treatment was never different from the control. Grouping the control and the 0.2x results and comparing the mean height increases with the 1x, 2x and 4x treatments allow us to see if additional difference could be detected. This analysis showed that the plants in the 1000 ppm (2x) treatment were significantly shorter than the combined group of control and 0.2x treated plants at week one and two. The same was true for the 2000 ppm (4x) treatment. There were on significant differences at week three or four. Plants in the 1x treatment showed no significant height reduction at any point. Thus, although ethephon is effective for reducing internode length, it is not effective for height control in general. Still, growers interested in marketing coleus without inflorescences showing and with greater branching would find ethephon to be a useful tool. The recommended rate, however, should be at least 2000 ppm.

9. GOOD RESEARCH PRACTICE STATEMENT: I acknowledge that I have read and followed the IR-4 Research protocol and completed this trial following good agricultural practice, or reported any deviations (note any changes from authorized protocol in narrative). The only deviation from the protocol was the addition of the 100 ppm (0.2x) ethephon treatment rate. Its inclusion was based on recommendations by a leading ethephon researcher.

SIGNATURE DATE

Dr. Heiner Lieth, PRINCIPAL INVESTIGATOR

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Figure 1. Stem cuttings of Coleus cv. “B” were allowed to root for two weeks in a mist bench with bottom heat of 75°F.

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Date

CIMIS ETo (in)

Precip (in)

Sol Rad (Ly/day)

Avg Vap (mBars)

Max Air Temp (°F)

Min Air Temp (°F)

Avg Air Temp (°F)

Max Rel Hum (%)

Min Rel Hum (%)

Avg Rel Hum (%)

Dew Pt (°F)

Avg wSpd (MPH)

Wnd Run (miles)

Avg Soil Temp (°F)

5/13/03 0.24 0 644 12.5 84.8 49.9 68 85 30 54 50.5 4.7 114.1 59.85/14/03 0.24 0 660 13.4 80.4 50.4 63.5 89 49 67 52.4 7.6 184 60.85/15/03 0.22 0 668 11.8 73.5 49.2 60.5 86 48 65 48.9 7.3 177.3 60.45/16/03 0.23 0 628 11.3 80.4 46.8 63.8 91 30 56 47.8 5.4 129.2 62.45/17/03 0.32 0 692 6.9 78.8 52.1 65.4 78 14 32 34.9 10.3 249.4 61.85/18/03 0.36 0 706 5.2 76.1 53.6 64.2 33 18 25 28 14.4 348 59.85/19/03 0.36 0 699 6.2 85.4 58.3 71.2 60 14 24 32.5 10.1 245 59.95/20/03 0.29 0 692 9.9 91 54 72.6 65 15 36 44.3 5.3 129 61.15/21/03 0.29 0 682 12.4 93.9 55.9 75.5 74 21 41 50.2 5.4 131.2 62.85/22/03 0.27 0 684 15.4 92.9 55.4 74.9 83 31 52 56.1 4.3 103.9 64.55/23/03 0.27 0 674 16.4 94.2 57.1 74 84 32 57 58 5.7 136.7 65.75/24/03 0.25 0 668 13.9 80.4 53.4 65 88 45 66 53.4 9.4 226.6 64.45/25/03 0.23 0 600 14.1 79.7 53.8 65 86 46 67 53.7 7.9 190 63.55/26/03 0.24 0 688 11.8 83.6 49.7 67.7 85 23 51 48.9 4.5 108.7 63.75/27/03 0.29 0 703 13.4 94.6 53 75.1 81 23 45 52.3 5 119.5 64.75/28/03 0.28 0 683 14 97.8 55.8 78 81 18 43 53.5 4.1 98 65.95/29/03 0.3 0 662 14.4 87.2 55.9 71.9 79 29 54 54.3 9.6 231.4 665/30/03 0.2 0 598 13.6 80.6 52.8 64.2 85 43 66 52.8 6.2 150.3 63.95/31/03 0.25 0 699 15.1 89.5 53.1 71.3 90 33 57 55.6 3.6 86.6 656/1/03 0.32 0 699 13 97.6 56.3 77.7 81 18 40 51.6 6.1 147 65.86/2/03 0.34 0 710 12.5 98 59.2 79.8 83 17 36 50.5 6.7 161.8 66.16/3/03 0.29 0 693 15.1 99.3 58.8 76.1 77 24 49 55.6 6 144.6 66.76/4/03 0.27 0 703 14.8 88.2 55.3 69.9 83 40 59 55.1 6.2 150.7 66.46/5/03 0.25 0 695 15.1 86.6 55 68.5 86 41 63 55.6 5.2 125.9 66.26/6/03 0.25 0 683 15.3 82.4 55.6 67.7 89 47 66 56 6.1 147.8 65.96/7/03 0.25 0 685 15.6 81.7 56.2 67.3 88 49 68 56.5 6.3 151.4 65.86/8/03 0.25 0 707 15.4 83.4 54.6 66.5 88 48 69 56.1 5.8 140.5 65.76/9/03 0.26 0 730 14.6 80.2 52.8 65.4 89 46 68 54.6 7.6 183.2 65.3

6/10/03 0.24 0 672 13.2 74.8 55 62.9 85 47 67 52 8.7 210.5 64.36/11/03 0.24 0 699 13.5 74.1 52 61.8 87 53 71 52.5 8.8 212.1 63.56/12/03 0.18 0 541 13.2 76.1 51.7 61.4 89 50 71 51.9 6.5 157.4 62.96/13/03 0.25 0 700 13.1 82.3 48.4 65.4 89 38 62 51.8 5.1 123.5 63.46/14/03 0.25 0 717 13.1 85.3 50.4 67.4 86 32 57 51.7 4.4 105 64.36/15/03 0.28 0 719 13.7 91.2 51.5 72.1 82 29 51 53 4.8 114.8 65.16/16/03 0.3 0 709 14.9 96.1 56.3 76.5 83 28 48 55.3 4.7 113 66.16/17/03 0.28 0 700 15.7 89.8 57.6 72.1 81 38 58 56.6 5.7 136.8 66.7

Total/Avg 9.15 0 682 13.2 86.1 54 69.4 82 33 54 51.2 6.6 158.4 64.3 Table 1. Environmental conditions during the experiment to determine effects of ethephon on Coleus cv. “B”. Data retrieved from CIMIS website http://www.cimis.water.ca.gov/ (Davis, Station #6)

PR.NO.: 13526A TRIAL: 2 DATE: 5/14/03

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Figure 2. Plants of Coleus cv. “B” two days after foliar application of 0, 100 ppm, 500 ppm, 1000 ppm or 2000 ppm ethephon (0, 0.2x, 1x, 2x or 4x recommended trate).

PR.NO.: 13526A TRIAL: 2 DATE: 5/14/03

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Figure 3. Symptoms of cupped and distorted leaves on Coleus cv. “B” attributed to phytotoxicity of ethephon.

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0123456789

10

0 1 2 3 4 5

weeks after treatment

Phyt

otox

icity

Rat

ing

Control100 ppm (0.2X)

500 ppm (1X)1000 ppm (2X)

2000 ppm (4X)

Figure 4. Average ethephon phytotoxicity ratings for Coleus cv. “B” plants four weeks post-treatment (n = 4). 0=NO INJURY; 1= reduced, distorted or cupped leaves, 10=COMPLETE KILL.

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10

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 100 500 1000 2000

ethephon (ppm)

# InflorescencesInternode length (cm)# Branches/plant

Figure 5. Effect of one foliar application of ethephon on Coleus cv. “B” plants four weeks post-treatment (n = 4).

PR.NO.: 13526A TRIAL: 2 DATE: 5/14/03

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Figure 6. Effect of one foliar application of ethephon on Coleus cv. “B” plants four weeks post-treatment.

0 ppm 100 ppm 500 ppm 1000 ppm 2000 ppm

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0

5

10

15

20

25

30

35

40

45

50

0 1 2 3 4 5

weeks after treatment

plan

t hei

ght i

ncre

ase

(cm

)

Control100 ppm (0.2X)500 ppm (1X)1000 ppm (2X)2000 ppm (4X)

Figure 7. Effect of one foliar application of ethephon on plant height increase for Coleus cv. “B” four weeks post-treatment (n = 4).

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0

2

4

6

8

10

12

14

16

0 1 2 3 4 5

weeks after treatment

plan

t dia

met

er in

crea

se (c

m) Control

100 ppm (0.2X)500 ppm (1X)1000 ppm (2X)2000 ppm (4X)

Figure 8. Effect of one foliar application of ethephon on plant diameter increase for Coleus cv. “B” four weeks post-treatment (n = 4).

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APPENDIX A PHYTOTOXICITY REPORT FORM for Coleus cv. “B”

ETHEPHON TREATMENT

RATE* oz ai/gal

PHYTO REP.

PHYTO RATE 5/16/03

PHYTO RATE 5/23/03

PHYTO RATE 5/30/03

PHYTO RATE 6/09/03

PHYTO RATE 6/17/03

CONTROL

0

1 0 0 0 0 0

CONTROL

0

2 0 1 1 1 0

CONTROL

0

3 0 0 0 0 0

CONTROL

0

4 0 0 0 0 0

CONTROL

0

MEAN 0 0.25 0.25 0.25 0

0.2X (100 ppm)

0.32

1 0 0 0 0 0

0.2X (100 ppm)

0.32

2 0 0 0 1 1

0.2X (100 ppm)

0.32

3 0 0 0 0 1

0.2X (100 ppm)

0.32

4 0 1 1 1 0

0.2X (100 ppm)

0.32

MEAN 0 0.25 0.25 0.5 0.5

1X (500 ppm)

1.6

1 0 1 1 0 1

1X (500 ppm)

1.6

2 0 1 1 1 0

1X (500 ppm)

1.6

3 0 1 1 1 1

1X (500 ppm)

1.6

4 0 0 0 0 0

1X (500 ppm)

1.6

MEAN 0 0.75 0.75 0.5 0.5

2X (1000 ppm)

3.2

1 0 0 0 0 1

2X (1000 ppm)

3.2

2 0 0 0 1 1

2X (1000 ppm)

3.2

3 0 0 0 1 1

2X (1000 ppm)

3.2

4 0 1 0 1 1

2X (1000 ppm)

3.2

MEAN 0 0.25 0 0.75 1

4X (2000 ppm)

6.4

1 0 1 0 1 1

4X (2000 ppm)

6.4

2 0 0 0 1 1

4X (2000 ppm)

6.4

3 0 1 0 1 1

4X (2000 ppm)

6.4

4 0 0 0 1 1

4X (2000 ppm)

6.4

MEAN 0 0.5 0 1 1

0=NO INJURY; 1= reduced, distorted or cupped leaves, 10=COMPLETE KILL *Be sure to provide units

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APPENDIX B EFFICACY REPORT FORM PLANT HEIGHT CONTROL for Coleus cv. “B”

ETHEPHON TREATMENT

RATE* oz ai/gal

REP.

Plant Height (cm) 5/16/03

Plant Height (cm) 5/23/03

Plant Height (cm) 5/30/03

Plant Height (cm) 6/09/03

Plant Height (cm) 6/17/03

CONTROL

0

1 8.5 16 25 33 40

CONTROL

0

2 10 18.5 28 35 40

CONTROL

0

3 8.5 16.5 26.5 43.5 54

CONTROL

0

4 7.5 14.5 26 41.5 56

CONTROL

0

MEAN 8.63 16.38 26.38 38.25 47.50

0.2X (100 ppm)

0.32

1 8 15 24 36.5 45

0.2X (100 ppm)

0.32

2 9 18 29 43 47

0.2X (100 ppm)

0.32

3 7 14 24 38 44

0.2X (100 ppm)

0.32

4 7 13.5 21 28.5 36

0.2X (100 ppm)

0.32

MEAN 7.75 15.13 24.50 36.50 43.00

1X (500 ppm)

1.6

1 10 18 28 36 44

1X (500 ppm)

1.6

2 10.5 17.5 26.5 38 44

1X (500 ppm)

1.6

3 9.5 18.5 27.5 32 39

1X (500 ppm)

1.6

4 7 11.5 21 39 54

1X (500 ppm)

1.6

MEAN 9.25 16.38 25.75 36.25 45.25

2X (1000 ppm)

3.2

1 6 12 21.5 37 49

2X (1000 ppm)

3.2

2 8 13.5 22.5 34 41

2X (1000 ppm)

3.2

3 8 13 20 32 44

2X (1000 ppm)

3.2

4 7.5 15 22.5 33 44

2X (1000 ppm)

3.2

MEAN 7.38 13.38 21.63 34.00 44.50

4X (2000 ppm)

6.4

1 7.5 11.5 18 31 39

4X (2000 ppm)

6.4

2 7 12.5 20.5 32 42

4X (2000 ppm)

6.4

3 6.5 11 17 30 38

4X (2000 ppm)

6.4

4 5.5 9.5 15 29.5 41

4X (2000 ppm)

6.4

MEAN 6.63 11.13 17.63 30.63 40.00

Efficacy Scale: Visual average of plant shoot heights above soil in pot (cm) *Be sure to provide units

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APPENDIX C EFFICACY REPORT FORM PLANT DIAMETER CONTROL for Coleus cv. “B”

ETHEPHON TREATMENT

RATE* oz ai/gal

REP.

Plant Width (cm) 5/16/03

Plant Width (cm) 5/23/03

Plant Width (cm) 5/30/03

Plant Width (cm) 6/09/03

Plant Width (cm) 6/17/03

CONTROL

0

1 5 9 11.5 14 15.5

CONTROL

0

2 4.5 8 11 19 18.5

CONTROL

0

3 4 13 12 13 18

CONTROL

0

4 4 7.5 10 11 13

CONTROL

0

MEAN 4.38 9.38 11.13 14.25 16.25

0.2X (100 ppm)

0.32

1 5.5 9 10 12 19

0.2X (100 ppm)

0.32

2 5 7.5 11 12 18.5

0.2X (100 ppm)

0.32

3 3.5 6.5 9 13 15

0.2X (100 ppm)

0.32

4 4 6 12 16 19.5

0.2X (100 ppm)

0.32

MEAN 4.50 7.25 10.50 13.25 18.00

1X (500 ppm)

1.6

1 5 6 8 16.5 19.5

1X (500 ppm)

1.6

2 5.5 6.5 13 17.5 19.5

1X (500 ppm)

1.6

3 4 8.5 9.5 17 16

1X (500 ppm)

1.6

4 4.5 8 10 12 14

1X (500 ppm)

1.6

MEAN 4.75 7.25 10.13 15.75 17.25

2X (1000 ppm)

3.2

1 3 6 9.5 11 10.5

2X (1000 ppm)

3.2

2 4.5 7 8 15 18

2X (1000 ppm)

3.2

3 3.5 6 7 14.5 13

2X (1000 ppm)

3.2

4 3.5 4.5 7 12 15

2X (1000 ppm)

3.2

MEAN 3.63 5.88 7.88 13.13 14.13

4X (2000 ppm)

6.4

1 3 5 8 12 14

4X (2000 ppm)

6.4

2 4 5 8 11.5 11

4X (2000 ppm)

6.4

3 3 4.5 8 16 15.5

4X (2000 ppm)

6.4

4 3 4 4.5 10 10.5

4X (2000 ppm)

6.4

MEAN 3.25 4.63 7.13 12.38 12.75

Efficacy scale: Plant diameter (cm) is average of two perpendicular measurements. *Be sure to provide units