Extension Cotton Specialists Working Group Presenting: Darrin Dodds

Efficacy and Agronomic Impacts of Commercially Available Plant Growth

Regulators Across the Cotton Belt

Extension Cotton Specialists Working Group

Presenting: Darrin Dodds

Extension Cotton Specialists Working Group

• Auburn University• Charles Burmester• Dale Monks

• University of Arkansas• Tom Barber

• University of Georgia• Steve Brown

• University of Florida• David Wright

• University of California – Davis• Bob Hutmacher

• Louisiana State University• Sandy Stewart

• North Carolina State University• Keith Edmisten

• Oklahoma State University• J.C. Banks

• Clemson University

• Mike Jones

• University of Tennessee

• Chris Main

• Texas AgriLife Extension Service

• Randy Boman

• Robert Lemon

• Virginia Tech

• Joel Faircloth

• University of Arizona

• Randy Norton

• Mississippi State University

• Darrin Dodds

• Kansas State University

• Stewart Duncan

Jost et al. 2006

Cotton Growth Habit

• Vegetative and reproductive development occur simultaneously

• Vegetative growth necessary to support reproductive growth– Excessive vegetative growth can be

detrimental

• Excessive vegetative growth:– Increased fruit abortion– Delayed crop maturity– Yield reduction

Fruit Abortion

• Fruit initiates at bottom of plant and progresses upward and outward (Ritchie et al. 2004)

• Excessive vegetative growth can shade the lower canopy and lead to abscission of early fruit (Oosterhuis 2001)

– Other factors can contribute to abscission of early fruit

Delayed Maturity and Yield

• Loss of early fruit may be compensated for when favorable conditions exist– Compensatory growth can result in

delayed maturity (Silvertooth et al. 1999)

• Yield reductions may occur due to reduced boll size (Jones and Wells 1998)

Figure 1. Boll size is correlated to position on fruiting branch. First and second position bolls tend to occur more frequently and weigh more than third position bolls. (Bednarz et al., 2005)

Boll

size

(g/b

oll)

Main Stem Node

Shading of the Lower Canopy

• Excessive shading can decrease micronaire of lower bolls (Eaton and Ergle 1954)

• Boll rot

• Penetration of pesticides

Fishel 2006

What is a Plant Growth Regulator?

• Chemicals used to alter the growth of a plant or plant part

• Agricultural research with PGRs began in the 1930’s– Acetlyene and ethylene– Enhanced flower production in

pineapple

How Do PGR’s Work?

• Three types of hormones are affected by foliar applied PGR’s– Gibberellins, Cytokinins, and Auxin

Taiz and Zeigler 1998

• Mepiquat reduces the concentration of gibberellic acid in the plantHake et al. 1991

• Mepiquat only affects new growth

Effects of PGR Application

• Reduction on total number of mainstem nodes– Reduction in internode length

Reddy et al. 1992

• Reduction in leaf area

• Shift in boll location

Figure 2. The effect of mepiquat on number of harvestable bolls per square meter on all sympodial branch fruiting positions at each main stem node (Kerby et al., 1986). Mepiquat generally causes a greater percentage of the total bolls to lower nodes on the plant.

PGR Applications and Cotton Yield

• Yield response to mepiquat has always been inconsistentBiles and Cothren 2000

• Positive yield effects are more likely to occur when fruit retention is reduced and vegetative growth is excessiveCook and Kennedy 2000

• Yield reductions more likely to occur when excessive rates of mepiquat are applied to stressed cotton

Objectives

• Examine several commercially available PGRs– Quantify effect of PGR application

on height, yield, and fiber quality

• Use these data to further refine PGR application recommendations

Agronomic Information

• Studies were conducted in 19 locations over two years across the cotton belt

• Planting date, seeding rate, fertility, insect management, and harvest aid applications were based on extension recommendations for each state

• Small plot research techniques were utilized at all locations

Varieties PlantedRegion States Variety

SoutheastNC, TN, VAAL, GA, SC

DP 117 B2RFDP 143 B2RF

DP 555 BR

Mid-South AR, LA, MS PHY 485 WRF

Southwest OK, TXFM 9063 B2RF

DP 555 BRST 5458 B2RF

Plant Growth Regulators

• Mepex– Mepiquat chloride– 0.35 lb ai/gal

• Mepex Gin Out– Mepiquat Chloride– 0.35 lb ai/gal– Kinetin – cytokinin

analog

• Pentia– Mepiquat

pentaborate– 0.82 lb ai/gal– Same amount of

mepiquat as Mepex

– Stance• Mepiquat chloride• Cyclanilide

– Auxin transport and synthesis inhibitor

• 0.736 lb mepiquat chloride/gal

Product Rate Application TimingMepex fb Mepex

8 oz/A10 oz/A

MHS2 WAIT

Mepex Gin Out fb Mepex Gin Out

8 oz/A10 oz/A

MHS2 WAIT

Stance fb Stance

1.5 oz/A2 oz/A

MHS2 WAIT

Stance fb Stance

2 oz/A3 oz/A

MHS2 WAIT

Pentia fb Pentia

8 oz/A10 oz/A

MHS2 WAIT

Stance fb Stance fb Stance

2 oz/A3 oz/A3 oz/A

MHS2 WAIT

NAWF = 5

Induce fb Induce

0.25 % v/v0.25 % v/v

MHS2 WAIT

Untreated

*** All PGR treatments included Induce at 0.25 % v/v ***

Data Collection• Data collected included:

– Plant height prior to initial PGR application– Plant height prior to second PGR application– Plant height two weeks after second PGR application– Plant height at the end of the season

• Total nodes

• Nodes above cracked boll

• Yield

• Fiber quality (HVI)

Plant Height Prior to 1st App.

14

14.5

15

15.5

16

16.5

17

17.5

18

Hei

ght (

in)

Mepex Mepex_GO Stance_1 Stance_2 Stance_3 Pentia Induce UT

PGR % of Untreated Height By RegionSoutheast Mid-South Southwest

Mepex fb Mepex

96 101 102


98 101 101

Stance fb Stance

97 101 101

Stance fb Stance

100 102 102


98 100 100

Pentia fb Pentia

98 100 100

Induce fb Induce

101 100 103

Untreated 100 100 100

Plant Height Prior to 2nd App.

20

22

24

26

28

30

Hei

ght (

in)


C C C B

C

C C A A

LSD (0.05) = 0.9


Mepex fb Mepex

84 92 93


85 94 95

Stance fb Stance

88 95 93

Stance fb Stance

88 95 99


87 93 95

Pentia fb Pentia

86 92 94

Induce fb Induce

99 102 100


LSD (0.05) 4 6 NSD

Plant Height 2 Wk After 2nd App.

25

28

31

34

37

40

Hei

ght (

in)


D BCD

B B BC

D A A

LSD (0.05) = 1.2


Mepex fb Mepex

82 84 82


84 87 86

Stance fb Stance

89 90 89

Stance fb Stance

88 89 85


86 88 88

Pentia fb Pentia

85 84 85

Induce fb Induce

100 102 100


LSD (0.05) 4 5 11

Final Plant Height

30

33

36

39

42

45

Hei

ght (

in)


B B B B B B A A

LSD (0.05) = 1.5


Mepex fb Mepex

81 86 94


79 90 85

Stance fb Stance

84 88 87

Stance fb Stance

84 89 90


84 88 88

Pentia fb Pentia

82 86 88

Induce fb Induce

98 105 97


LSD (0.05) 5 6 7

Total Nodes

16

16.5

17

17.5

18

18.5

19

19.5

Num

ber


B B B B B B A A

LSD (0.05) = 0.6

PGR Total Nodes By RegionSoutheast Mid-South Southwest

Mepex fb Mepex

17.5 17.5 19.4


17.4 17.4 18.4

Stance fb Stance

17.7 17.7 18.8

Stance fb Stance

17.8 17.8 19.0


17.8 17.8 18.5

Pentia fb Pentia

17.7 17.7 18.8

Induce fb Induce

18.9 18.9 20.3

Untreated 19.0 19.0 21.3

LSD (0.05) 0.7 NSD 1.1

Nodes Above Cracked Boll

1.5

2

2.5

3

3.5

4

Num

ber


LSD (0.05) = NSD

PGR Nodes Above Cracked Boll By RegionSoutheast Mid-South Southwest

Mepex fb Mepex

3.8 3.2 3.7


4.0 3.4 2.0

Stance fb Stance

4.0 2.9 2.3

Stance fb Stance

4.0 3.1 3.3


4.1 3.8 2.7

Pentia fb Pentia

4.2 2.9 2.4

Induce fb Induce

4.0 3.9 2.6

Untreated 4.1 3.4 3.9

LSD (0.05) NSD NSD 1.1

Lint Yield

1000

1025

1050

1075

1100

1125

1150

1175

1200

1225

lbs/

acre


LSD (0.05) = NSD

PGR Lint Yield By RegionSoutheast Mid-South Southwest

Mepex fb Mepex

1290 1053 1137


1376 1102 1106

Stance fb Stance

1314 1008 1115

Stance fb Stance

1315 1088 1117


1302 1042 1147

Pentia fb Pentia

1355 1136 1065

Induce fb Induce

1358 1025 1129

Untreated 1296 1034 1129

LSD (0.05) NSD NSD NSD

PGR Mic Staple Strength UniformityMepex fb Mepex

4.5 1.14 30.4 82.6


4.4 1.14 30.4 82.1

Stance fb Stance

4.4 1.14 30.4 82.3

Stance fb Stance

4.5 1.14 30.4 82.3


4.4 1.15 30.8 82.4

Pentia fb Pentia

4.4 1.15 30.3 82.3

Induce fb Induce

4.5 1.13 30.0 82.1

Untreated 4.5 1.12 29.9 82.3

LSD (0.05) NSD 0.01 NSD NSD

PGR Staple By RegionSoutheast Mid-South Southwest

Mepex fb Mepex

1.14 1.14 1.16


1.11 1.14 1.16

Stance fb Stance

1.13 1.13 1.17

Stance fb Stance

1.12 1.12 1.17


1.13 1.15 1.17

Pentia fb Pentia

1.13 1.14 1.17

Induce fb Induce

1.09 1.12 1.16

Untreated 1.09 1.11 1.15

LSD (0.05) 0.02 0.01 NSD

PGR Strength By RegionSoutheast Mid-South Southwest

Mepex fb Mepex

31.3 30.4 29.7


31.1 30.0 30.2

Stance fb Stance

31.1 29.9 30.2

Stance fb Stance

31.1 30.2 30.7


30.8 31.0 30.4

Pentia fb Pentia

31.6 29.8 29.8

Induce fb Induce

30.8 29.8 29.5

Untreated 30.3 29.7 29.9

LSD (0.05) NSD 0.8 NSD

Conclusions

• All PGR’s examined provided similar plant height reductions

• PGR application did not enhance lint yield

• Total number of nodes and NACB were similar regardless of PGR applied

Conclusions

• Mic and uniformity were similar whether a PGR was applied or not

• Minor differences in staple length and strength were observed

• PGR product selection should be based on individual grower needs as opposed to a specific product

• PGR application decisions should be made on a field-by-field basis each year

Questions

Extension Cotton Specialists Working Group Presenting: Darrin Dodds

Documents

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