September 28, 2001                                                                    http://commodities.caes.uga.edu/fieldcrops/cotton/

 

IN THIS ISSUE:

Crop Situation

Insect Damage Survey

Aim Revisited

Additional Observations on Aim

Important Dates

 

Crop Situation.  (Brown) As of the end of September, Georgia producers have picked about 15 percent of a projected 2.1 million bale crop.  Sustained dry weather is needed to get the crop out with maximum yield and quality.  Early reports are that the crop is Aweighing heavy,@ meaning yields are turning out slightly better than expected.  In addition, suspicions are that Georgia lint quality may show improvement over past years...if significant rainfall events don=t continue.  We hope this trend continues and that our quality is as good as we hope.

 

Insect Damage Survey.  (Roberts) In early to mid-September, we conducted a survey to estimate boll damage caused by insect feeding.  We appreciate the assistance of the many cooperating county agents.  We surveyed 82 fields, 42 non-Bt and 40 Bt fields.  Fields varied from 0 to 40 percent open boll, with an average of 9 percent open boll.  In each field, approximately 100 bolls were collected, 50 bolls from two locations.  All bolls that would significantly contribute to yield were collected from plants so as not to bias the sample toward any area of the plan canopy.  Bolls were opened and examined internally and evaluated for Aworm@ damage and Abug@ damage.  Damaged bolls were defined as having at least one lock with significant discoloration and/or rot (no chance for that lock to contribute to yield).  Insecticide application records will be obtained for each field and the data will be further analyzed.  Preliminary results include:

 

Boll Damage Survey	Percent Damage
	Total	Non-Bt	Bt
AWorm@ Damage	2.74	3.64	1.81
ABug@ Damage	2.94	2.64	3.25

 

What do these data mean?  Since this is the first year of a survey of this type, we are not sure.  Are these numbers high or low?  We do know that greater than 5 percent of the bolls had insect damage.  In some instances the entire boll was lost, in others only one or two locks were lost, and we believe remaining locks would fluff and be pickable.  As a whole, this was a relatively light insect year.  Corn earworm and tobacco budworm populations were low during June

and July.  However, some growers faced heavy and difficult-to-control populations of worms in August.

Bug numbers varied from light to heavy.  This year was a good example of HOW and WHY scouting pays.  Some fields required few or no sprays, while others required timely intervention with insecticides to minimize damage and maximize profits.  Again, good scouting is critical to good management.

 

As defoliation and harvest begin, growers may want to take a few moments to evaluate their insect management programs.  Bug damage in the upper canopy is high in some fields which is very easy to detect when cutting bolls to check maturity.   Examination of open bolls lower in the canopy or bolls frozen to the plant will also allow growers to assess insect damage.

 

Aim Revisited.  (Jost)  There is still much discussion and many questions concerning the use of Aim as a harvest-aid.  The mode of action, chemistry and background information were discussed in last month=s newsletter.  Some Georgia data has been generated, and a sample is presented in the following table.

 

Harvest-Aid

Rate

Defoliation 7 DAT (%)

Terminal Regrowth 16 DAT (%)

Basal Regrowth 16 DAT (%)

Def

1.75 pt/A

85 bcd

98 a

88 a

Dropp

0.2 lb/A

74 e

13 e

15 a

Def

1 pt/A

93 a

25 de

35 b

Dropp

0.1 lb/A

Def

1.25 pt/A

93 ab

98 a

100 a

Ethephon

1.33 pt/A

Def

5 oz/A

91 abc

28 de

30 b

Dropp

0.1 lb/A

Ethephon

1.33 pt/A

Aim

0.66 oz/A

81 de

88 ab

100 a

Ethephon

1.33 pt/A

COC

1% v/v

Aim

0.66 oz/A

89 a-d

43 cd

28 b

Dropp

0.1 lb/A

COC

1% v/v

Aim

0.66 oz/A

88 a-d

63 bc

83 a

CottonQuik

2 qt/A

Leafless

12 oz/A

85 cd

13 e

10 b

COC

1 pt/A

 

In general, these data suggest that Aim works best in conjunction with either Dropp or CottonQuik rather  than with ethephon.  However, in other tests it appears that the chance for desiccation increases with the use of CottonQuick.  This seems to be more of a problem in cotton that is still green and more rank.  The test that this data was taken from was on dryland cotton that was at least 90% open and ready to defoliate.

Another trend that can be observed from this data is that the combination of lower rates of Def and Dropp had significantly greater defoliation than the high rate of either one alone.  This serves as another argument to use diverse chemistries in tank-mixes.  Also, as expected, the data shows that the use of Dropp in tank-mixes significantly reduces terminal and basal regrowth. 

 

Additional Observations on Aim.  (Brown) Though Aim has been evaluated in grower fields and research trials over the past several weeks, we still have much to learn about its niche as a harvest aid.  It is particularly effective on morningglories but weak on sicklepod and grasses.  How good it is as a stand-alone defoliant has been difficult to determine because most uses have included substantial rates of other products.  It is a frequent tank mix partner replacing DEF/Folex.  Aim works fast, leaf effects are observable in just a day or so.  Sometimes treated leaves appear to be desiccated, but they do come off a few days after treatment.

 

Important Dates.

December 11 & 12, 2001       Cotton Production Workshop - RDC, Tifton, GA

January 8-12, 2002              2002 Beltwide Cotton Conference - Atlanta, GA

 

 

Prepared by: