Preparing for Cotton Harvest without Chemicals

USDA-ARS and the Propane Education and Research Council

Thermal Defoliation Field Trial Locations and Dates


Thanks to the cooperation of many institutions and individuals, thermal defoliation
has been tested in numerous varieties at many locations over several seasons.

Six-row Commercial Thermal Defoliator


The new commercial-scale thermal defoliator constructed by Ag Industrial Manufacturing, Inc., Lodi, CA.
It was cut to half its original length for the 2008 season to make it more maneuverable.


Despite the modification, it is still a large machine.
Covering six 30 inch rows it is capable of treating 5 acres per hour.


Cotton in the foreground treated earlier today is already desiccating.


The leaves on rows treated yesterday are brown and dry this morning.
Once aligned with the rows, the thermal defoliator steers itself.


The end of the first shift, Oct 22, 2008.


Louis the night driver turns the machine into another row.
80 acres were treated in three days.

Two-row Prototype Thermal Defoliator


2008 Treating research plots to support studies at the University of California, Shafter.
These trials are part of an EPA grant assessing the impact of thermal defoliation.


Unloading to treat organic cotton in the Midland-Odessa part of Central Texas (2008).
When the oil wells run dry there will still be farming.



Weslaco, TX July 2004. Scientists were almost as thick as the cotton.

6 hours later

The impact of thermal treatment is visible the day of treatment.

West Side

At the University of California's West Side Research and Extension Center.


Producers attending the USDA-ARS and UC Shafter Field Day check out cooked cotton.


Refueling while treating stripper cotton on the High Plains of West Texas.


Thermal treatments at New Mexico State University's Plant Science Research Center near Las Cruces.


The six treatment and harvest date combinations investigated in Las Cruces.
Numbers indicate the days between treatment and harvest.

La Union

A commercial producer of organic cotton tests the thermal defoliation apparatus on Acala and Pima varieties.

One-row Experimental Thermal Defoliator

The predecessor apparatus was a tractor-towed one row device.

Temp Set

Adjusting treatment temperature (between 250 and 350 F) in 2002.

2002 Treats

2002 thermal defoliator shows its stuff.


Entomologist Brad Lewis monitors leaf respiration immediately after thermal treatment.
Professor Lewis quantified insect mortality in 2001.
Thermal treatments had significantly fewer whiteflies and aphids.


Special thanks to Cooperating Scientists:
Carlos Armijo (USDA-ARS Las Cruces, NM)
Alan Brashears (USDA-ARS Lubbock, TX)
Reginald Fletcher (USDA-ARS Weslaco, TX)
Allan Showler (USDA-ARS Weslaco, TX)
Michael McGuire and Jay Bancroft (USDA-ARS Shafter, CA)
David McAllister III (USDA-ARS Clemson, SC)
Brad Lewis (New Mexico State University)
Robert Hutmacher and Larry Godfrey (University of California)
(Along with Treanna Pierce, Pete Goodell, Bruce Roberts and Brian Marsh)
And Wayne LePori (Texas A & M University)
Cooperating Farmers:
Don Cameron (TerraNova Ranch, Helm, CA)
Doci Alvarez (Alvarez Farms, La Union, NM)
Frank Williams and Mark Fickett (Firebaugh, CA)
Paul Goodman (Dos Palos, CA) and Frank Everidge (Midkiff, TX)
Ed Scott (UC West Side Research and Extension Center)
Gary Lawrence and Mark Pacheco (NMSU Leyendecker PSRC)
Other Key Collaborators:
Paul Burkner and Kevin Wilkerson (Ag Industrial Mfg)
Marcia Gibbs (Sustainable Cotton Project)
Steve Jaeger (Railroad Commission of Texas)
Bryan Stegall (NM Propane Dealers Association)
Mark Leitman (Propane Council, Washington, DC)
John Lloyd (USDA-APHIS), Chuck Melton (Fresno County)
Ramon Alvarez and Tommy Rodriguez (NMSU Transportation)
and many others.

Funding provided by the Propane Education and Research Council is gratefully acknowledged.


2012. Funk, P. A., Armijo, C. B., Hawkes, G. M. and Libbin, J. D. Cotton thermal defoliation economics. J. Am. Soc. Farm Managers & Rural Appraisers. 75(1):29-42.
2007. Fletcher, R. S., Showler, A. and Funk, P. A. Surveying thermally-defoliated cotton plots with color-infrared aerial photography. Crop Management.
2006. Funk, P. A., Armijo, C. B., Showler, A., Fletcher, R. S., Brashears, A. D. and McAlister, III, D. D. Cotton harvest preparation using thermal energy. ASABE Transactions. 49(3):617-622.
2006. Bancroft, J. S., Hutmacher, R., Godfrey, L., Goodell, P., Mcguire, M. R., Funk, P. A. and Wright, S. Comparison of Sticky Cotton Indices and Sugar Composition. Journal of Cotton Science 10:97-104.
2006. Showler, A. Funk, P. A. and Armijo, C. B. Effect of Thermal Defoliation on Cotton Leaf Desiccation, Senescence, Post-harvest Regrowth, and Lint Quality. Journal of Cotton Science 10:39-45.
2004. Funk, P. A., Armijo, C. B., McAlister, III, D. D. and Lewis, B. E. Experimental Thermal Defoliator Trials. Journal of Cotton Science 8:230-242.

Last updated 03 Oct 2012