NC State University|Crop Science|College of Agriculture and Life Science|NC Cooperative Extension
Keith Edmisten, Cotton Extension Specialist
Department of Crop Science
North Carolina State University

It is still a little too early to say what products may be needed for any given field at this point. Some of the early cotton in dry area may be ready soon. We have a lot of late cotton that we may need to delay defoliation until sometime in October to try to maximize yields.

There are some new products out there. Many are generic products with the same active ingredient as one of our standard defoliation products. If you have a question about a defoliant you have never heard of before, the first thing you should do is check the active ingredients and compare that to the active ingredients in the standard defoliants you are familiar with. The common chemical name for the active ingredient(s) in a defoliant is given it Cotton Information and the North Carolina Agricultural Chemicals Manual. They are also listed here in Table 3.

Resource is a new defoliant with a different active ingredient. Although the active ingredient is new it is a PPO inhibitor similar to Aim and ET. We have limited experience with Resource you can see the results from last year in Table 1. In table 2 you see Resource compared to older standards and Aim. The results with Resource look very similar to Aim in this test. We did not see a lot of desiccation in the trials last year as there was not a lot of juvenile growth at the time of defoliation. One thing we have seen in the past in rank cotton with a lot of juvenile growth is desiccation of the juvenile growth from PPO inhibitors like Aim, ET and Resource. This is usually very noticeable at 7 DAT but the desiccation tends to be transient and the plots usually look good at 14 DAT. The PPO inhibitors are sometimes used in a two step defoliation in some states that tend to have more juvenile or excessive growth. These two step application methods have worked well in research here but in most case did not improve a one step application enough to make the second application worthwhile.

Table 1. Resource defoliation test in 2006
Spray vol: 15/gal/ac Mix Size: 3 gallons (min .52314)

Trt
No.

Treatment
Name

Form
Conc

Form
Type

Rate

Rate
Unit

%
Defoliation
14 DAT

%
Desiccation
14 DAT

% Open
14 DAT

% Terminal
Regrowth
21 DAT

% Basal
Regrowth
21 DAT
1 Resource 10.0 EC 4 fl oz/a
74.25 c
6.75 a
88.5 bc
23.75 b
35 b
Prep

6

SL 20.8 fl oz/a
Crop Oil Conc L 16 fl oz/a
2 Resource 10.1 EC 4 fl oz/a
88.25 ab
6.25 a
92.5 a
2.75 cd
16.25 cd
Prep 6 SL 20.8 fl oz/a
Induce (NIS) L 0.25 % v/v
3 Resource 10.1 EC 4 fl oz/a
88.75 ab
27.5 a
93.25 a
1.25d
18 cd
Finish 6 Pro 6 SL 21.3 fl oz/a
Induce (NIS) L 0.25 % v/v
4 Resource 10.1 EC 6 fl oz/a
86.75 ab
8.25 a
93 a
6 cd
16.5 cd
Prep 6 SL 20.8 fl oz/a
Crop Oil Conc L 16 fl oz/a
5 Resource 10.1 EC 6 fl oz/a
83.75 b
8.25 a
91.25 ab
8.5 c
21.75 c
Prep 6 SL 20.8 fl oz/a
Induce (NIS) L 0.25 % v/v
6 Resource 10.1 EC 6 fl oz/a
92.5 a
9.25 a
93.75 a
0 d
11.75 d
Finish 6 Pro 6 SC 21.3 fl oz/a
Induce (NIS) L 0.25 % v/v
7
Untreated Control
38.75 d
0 a
86 c
45 a
47.5 a
LSD
6.791
19.929
2.903
6.618
9.241

 

Table 2. Beltwide defoliation test, 2006.
Rating Date Type
% Open
7 DAT
% Def
7 DAT
% Desiccation
7 DAT

% Open
14 DAT

% Def
14 DAT
% Desiccation
14 DAT
Rating Date
1/Oct/2004
1/Oct/2004
1/Oct/2004
7/Oct/2004
7/Oct/2004
7/Oct/2004

Trt

No.

Treatment

Name

1
2
3
4
5
6
1 Untreated
21.25 c
30.00 c
0.00 a
15.00 d
32.50 c
0.00 b
2 Tribufos
83.00 ab
86.50 ab
0.00 a
92.00 a
93.50 a
0.25 b
Ethephon
0.00 b
Thidiazuron
3 Dimethipin
85.25 ab
89.25 a
0.00 a
81.50 bc
87.75 ab
0.00 b
Tribufos
Ethephon
Agridex
4 Thidiazuron
73.00 b
77.75 b
0.00 a
84.50 b
89.00 ab
0.00 b
Ethephon
5 Tribufos
80.50 ab
85.00 ab
0.00 a
77.25 c
83.75 b
0.00 b
Ethephon
6 Aim
82.75 ab
85.25 ab
85.25 ab
93.75 a
95.75 a
1.50 a
Ethephon
Thidiazuron
80/20 NIS
Aim
Agridex
7 Resource
87.00 a
88.75 ab
11.180
93.50 a
95.50 a
1.75 a
Prep
Agridex
Resource
Agridex
LSD (P=.05)
13.298
11.180

0.842

6.367
8.231
0.842

 

Table 3. Active ingredients in some commonly used defoliants.
Defoliant Active Ingredient 1

Active Ingredient 2*

Accelerate endothal  
Aim carfentrazone  
CottonQuik ethephon AMADS
Cyclone paraquat dichloride  
Def tribufos  
Dropp thidiazuron  
ET pyraflufen  
Finish ethephon  
Free Fall thidiazuron  
Ginstar thidiazuron diuron
Harvade dimethipin  
Klean-Pik thidaizuron  
Leaf-all Dodium cacodylate cacodylic
Leafless dimethipin thidiazuron
Prep ethephon  

*Second active ingredient given for defoliants with more than one active ingredient.

MFX is a 2 lb/gal active foam of ethephon that will be available this year.
FirstPick is a new form of CottonQuik. Data on FirstPick will appear in the next Carolina Cotton Note.

2006 - Carolina Cotton Notes

NCSU Cotton Team


2006 crop science©
last modified September 7, 2006 9:45 AM
page by Gary Little