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Thermal Defoliation in Acala and Pima Cotton – Defoliation Performance, Late Season Insects

The Regents of the University of California-Davis
Office of Research, Sponsored Programs
One Shields Ave
Davis, CA 95616

Larry D. Godfrey, Entomologist
530-752-0473
ldgodfrey@ucdavis.edu

Purpose Statement

To evaluate the suitability and performance of thermal defoliation of acala and pima cotton as an alternative technology to chemical defoliation and pesticides. A thermal defoliation method of preparing the crop for harvest is independent of the weather, reduces the need for insecticides, eliminates the increased use of harvest-aid chemicals, and protects the crop from insect sugar deposits.

Project Duration: 12 months

Funding Request
Budget Category Funding Requested Matching Non-Federal Funds Matching
Federal Funds
First Year Funding
$47,000
0
0
Second Year Funding
0
0
0
Total Funding
$47,000
0
0

Executive Summary

The Regents of the University of California-Davis seeks financial support from the US EPA to enhance a project that reduces the health and environmental risks associated with chemical use in agriculture through the demonstration and evaluation of the effectiveness of a thermal crop cultivation technology for acala and pima cottons. The project desires to provide an environmentally advantageous, cost-effective alternative to chemical defoliation and pesticides.

Evaluations of the suitability and performance characteristics of cotton harvest aids for acala and pima cottons are the basis of comparisons between thermal defoliation and chemical harvest aid methods proposed for this project. In western U.S. the challenges of increased difficulty with Acala and Pima defoliation have typically been dealt with by using higher recommended chemical rates in most cases, and sequential applications of two or more types of chemicals when crop and weather conditions warrant. For these reasons, some typical or even moderately vigorous Pima and Acala fields under California conditions should represent good evaluation conditions to compare thermal versus chemical defoliation.

Objectives

Rationale

The project will carefully and scientifically analyze and compare thermal and chemical defoliation effectiveness for promotion of leaf desiccation and defoliation, and inhibition of troublesome plant regrowth. Current field practices rely heavily on chemical defoliants. If determined successful, thermal defoliation will lead to avoided or reduced use of chemical defoliants that represent routine exposure risks for the environment and human health. Environmental costs associated with chemical defoliation include water and air quality impacts; propane fuel used to produce defoliating heat will not contaminate groundwater or soils, and propane combustion emissions during defoliation are inherently low in ambient air criteria pollutants listed under the federal and CA Clean Air Acts. Chemical defoliants typically contain reactive organic compounds that lead to increased air pollution, and air regulations increasingly aim to reduce volatiles used in chemical pesticides, defoliants, and harvest aid materials. Lint quality will be analyzed and compared under the two defoliant regimes; project analysis and comparisons aims to determine levels of protection potential for lint quality using thermal defoliation. If found effective, thermal defoliation is anticipated to produce direct and indirect environmental benefits over traditional chemical treatments, along with reductions in chemical-related human health risks since no chemicals are used in thermal defoliation. Costs and time budgets for the two defoliant study regimes will be carefully recorded and evaluated. Chemical defoliant time and cost requirements are understood. Thermal defoliation requirements are not. This project will attempt to identify the circumstances under which thermal defoliation can be competetive with chemical defoliation methods. If cost-effective, thermal defoliation is anticipated to be environmentally superior while reducing potenial health risks associated with chemical exposures. Benefits for late-season insects and sticky cotton will be similarly evaluated. Pima and Acala cotton types are prone to late season insect damage, and sticky cotton caused by insect honeydew leads to significant increased chemical control costs, processing costs, and crop damage. Thermal defoliation may hold particular benefits for late season cotton, since heavy leaf canopies inhibit effective applications of pesticides. Again, reduction in chemical treatments with use of effective thermal defoliation is expected to produce direct and indirect environmental, human health, and pollution prevention benefits.

Approach and Methods

Field comparisons of thermal defoliation and chemical harvest aid approaches will be done in replicated strip treatments in a minimum of two locations each in Pima and Acala types of cotton. Selection of field sites for the comparisons will be made to represent at least one field of each cotton type with relatively typical low to moderate late-season plant vigor and boll load; and one field with more vigorous late-season vegetative growth. These differing crop conditions will help test performance under a range of plant growth conditions growers often experience at defoliation time.

Plant conditions at defoliation timing will be characterized using plant mapping to describe height, node and leaf counts and relative boll load and percent open boll. The choice of timing to initiate chemical harvest aid applications will be according to recommendations developed by the University of California based on percent cracked boll, open boll percentage and harvestable boll maturity. Choice of harvest aid chemicals to use will be based on crop condition and best-performing materials in long-term University field tests. The need for sequential chemical applications (more than one application and material will be determined based on field evaluations of efficacy of defoliation / desiccation), as done in University field tests. Timing of chemical applications will be recorded and approximate material and application costs for chemical harvest aid applications will be recorded.

Thermal defoliation timing will be done to match the first chemical harvest aid application. If field plot area and resources allow, two different timings of thermal defoliation can be evaluated if fields differ in cotton boll distribution and maturity. Data collection will include evaluations of:

The size of treated areas will be large enough to allow large-scale machine harvest (for yield determination) and collection of fiber samples (for ginning and fiber quality analyses). Six-pound samples of fiber will be collected from each field replication, run through the UC Shafter REC research gin, and evaluated for gin turnout, trash percentage, and HVI fiber quality.

Insect Monitoring: Late-season infestations of cotton aphid (Aphis gossypii) and sweet potato whitefly Strain B (Bemisia tabaci also called Bemisia argentifolii) have the potential to significantly reduce cotton lint quality. These insects remove sap from the plants and excrete the excess carbohydrates as a substance descriptively known as “honeydew”. This substance when deposited on cotton lint inhibits the ability to gin, and particularly to process and mill the cotton into the finished product. Insecticides are used to mitigate this situation but even their effectiveness is compromised during this late-season window. Reasons including the dense cotton canopy, insect feeding location on the leaf undersides, limited ability of the plants to absorb systemic insecticides, low numbers of insects needed to cause sticky cotton, and limitations in insecticides available for use because of the pre-harvest intervals have made the late-season insect situation challenging. Thermal defoliation may offer a unique advantage over the chemical defoliation in that late-season insect control may be achieved. In locations where late season insects (aphids and/or whitefly are present), separate fiber samples will be collected for stickiness testing.

Insect populations will be monitored weekly in prospective study fields for the month before defoliation. Samples of the fifth main stem node leaf (from the plant terminal) will be collected (10 leaves per sample and 8 samples per study area) and the number of aphids and whitefly nymphs will be quantified in the lab. Whitefly adult populations will be determined by leaf turn samples in the field of the same leaf (10 leaf turns each in 8 locations). Numbers of whitefly adults will be counted on each leaf. Following defoliation, insect populations will be quantified by assessing the number of insects per plant and the percentage of plants with insects. After removing the majority of the leaves through defoliation, the insects are often concentrated on a few leaves/plants, i.e., those that are still green. Cotton lint will be hand-harvested; six-pound samples of fiber will be collected from each field replication, run through the UC Shafter REC research gin, and evaluated for gin turnout, trash percentage, and HVI fiber quality. These samples as well as those from the large-scale machine harvest will be assessed for lint stickiness at the Texas Tech University International Textile Center. A study site will also be available on the Shafter Research and Extension Center for this objective. At this site, insect populations can be allowed to develop. Since the occurrence of sticky cotton in grower fields in the 2001 season, most growers have a “zero-tolerance” for late-season insects and therefore it can be challenging to find research locations.

Background Information

Evaluations of suitability and performance of any cotton harvest aid chemicals are based on several areas of performance, including: (1) ability to desiccate leaf tissue and cause leaves to drop off the cotton plants, reducing leaf and stem trash content at harvest; (2) reduce regrowth of new leaves after the harvest aid application; (3) cause little or no negative impacts on fiber or seed quality. In addition, some chemical harvest aid materials can increase the speed of opening of some of the later-developing, unopened bolls. These performance characteristics are the basis of comparisons that can be made between thermal defoliation and chemical harvest aid methods. Several recent field evaluations have also shown that populations of late season insects (silverleaf whitefly, cotton aphids) with potential to impact fiber quality and stickiness can also be affected by the duration of live leaf retention and regrowth following harvest aid applications.

Numerous field evaluations done over many years by Roberts, Wright and Vargas (University of CA Coop. Extension) have demonstrated that under conditions in the western U.S., most types of Acala cotton (a high fiber-quality subgroup of Upland cottons) are more difficult to defoliate than most other Upland (Gossypium hirsutum) cottons. In western U.S., Pima cottons (Gossypium barbadense) have been shown to require different defoliation approaches, and usually are considered even more difficult to defoliate than the Acalas. With chemical defoliation methods, the challenges with Acala and Pima defoliation have typically been dealt with by using higher recommended chemical rates in most cases, and sequential applications of two or more types of chemicals when crop and weather conditions warrant. These differences in recommended rates and sequential applications are evident in looking at the California chemical labels. For these reasons, some typical or even moderately vigorous Pima and Acala fields under California conditions should represent good evaluation conditions to compare thermal versus chemical defoliation.

Resources

Paul Funk (USDA-ARS Las Cruces NM); Larry Godfrey (UC Davis Entomology), Bob Hutmacher (UC Davis Plant Science and UC Shafter REC), Steve Wright (UC Coop. Ext. Tulare and Kings Co.)

Measures and Outcomes

“What will be different as a result of this project?” Thermal defoliation of cotton holds substantial potential to reduce current reliance on chemical defoliants, a goal embraced by the Pesticide Environmental Stewardship Program (PESP). Critical operational and cost parameters of thermal defoliation are not well known, however, and are therefore primary targets for research under this proposed project. Thermal defoliation may offer a steady, ready, reliable, portable, and environmentally superior option for control of troublesome insects and plant structures in cotton production. Reducing insecticide and defoliant use with a cost-effective thermal defoliator should lead to direct and indirect environmental benefits to water, soil, and air quality resources, while bolstering federal, state, and local programs aimed at reducing environmental and human exposures to toxic or hazardous pesticides. This project’s comparative study of important functional parameters between chemical and thermal defoliation regimes will lead to important, objective information that may then form the basis for future actions or decisions undertaken by agriculturists or agriculture agencies. Without important information to be gained from this University project, cotton agriculturists can be expected to continue use of traditional chemical-based treatments to defoliate and reduce damage caused by insects. Success for the project will be primarily measured by development of comparative cost and operational data (focusing on leaf desiccation, defoliation, regrowth inhibition, effects on lint quality, late season pest control, etc.) between the two defoliation regimes under highly monitored conditions at the University field research station in Shafter, CA. Environmental benefits from the project will be characterized for potential extrapolation to larger implementation scenarios. While the study is not aimed at producing risk reduction measures per se, its findings should assist agency efforts to reduce negative impacts associated with pesticide and herbicide use in cotton farming.

Outreach

The advanced prototype USDA-ARS thermal defoliation field equipment can be shown and demonstrated at University cotton field days, and data collected in these field trials will be the basis of on-farm or University Research and Extension Centers (Shafter REC in Kern County and West Side REC in Fresno County) Cotton Field Day demonstrations. These field days are held in September and attended by key representatives of the cotton industry. These field demonstrations or discussions will be publicized using University newsletters or the county and UC cotton websites (cottoninfo.ucdavis.edu) as well as through industry channels. Pest management results from this study will be incorporated into the UC Pest Management Guidelines (IPM.ucdavis.edu).

Data collected in field trials will be discussed in University Cotton newsletters either at the county level or in the CA Cotton Review newsletter, with articles prepared by the study cooperators. Results will be presented to the cotton scientific industry, as well as producers, at the Beltwide Cotton meeting held each January. Plans would be to replicate field trial treatments at each location in order to allow statistical analysis of field data for presentation in informal and more formal journal publications.

PERC will commence a communication and outreach program through the print and electronic media that will increase the awareness of the propane fueled apparatus and potentially gain market share as a viable alternative to pesticides and other crop cultivation chemicals. This initial outreach communications program is vital to build incremental awareness of the project and its partners and the role the Propane Council will play in creating new opportunities in the Integrated Pest Management (IPM) community through new product research and broad-based communications. The intended audience will include cotton producers, academia, the Sustainable Cotton Project, the Chile Pepper Task Force, organic growers associations, cotton ginning and growers associations, the federal government (including the USDA and the IPM Program), and the propane industry.

PERC enjoys a nationwide stature in its ability to showcase the commodity and reach out to literally millions of consumers through various media. Consumer traffic on www.usepropane.com more than tripled in 2004, with more than 100,000 searches of the Find a Propane Retailer feature of the site. Propane kicked off the 2005 television campaign on February 20 with a presence in the Daytona 500 on the FOX broadcast network. The TV campaign will continue with other NASCAR events on NBC as well as on cable networks including HGTV, The Weather Channel, and Country Music Television. Wide-ranging radio, online, and print advertising will round out the 2005 campaign.

With this project PERC will launch a focused communications strategy supported by the branding campaign, PROPANE Exceptional Energy®. The outreach program will include various communications tools, public relations, and web-based initiatives aimed at key farmer and consumer audiences, as well as the propane industry. The overall strategy will integrate tactical initiatives that create proactive, dynamic communications in order to build a positive image and increase existing and potential consumer knowledge of this apparatus and its environmental benefits.

Sustainability

This project will help to demonstrate the feasibility of the thermal cultivation concept to a wider audience and lessen the use of chemicals and pesticides. Cotton production is anticipated to increase with population growth. If this project is successful in proving the benefits of thermal cotton defoliation, sustainability is assured.

We believe that this application is also useful for chile pepper crops as an alternative to salt defoliation (which reduces soil fertility). The results of all thermal cultivation field trials will be made available to the Chile Pepper Task Force, a regional collaboration of growers, processors, scientists, and manufacturers working to realize a system-wide development of technological advances required for harvest mechanization (www.chiletaskforce.org). Results could also be valuable for chemical-sensitive crops planted near cotton fields, such as citrus or lettuce.

PERC is an important and logical project partner and is committed to continuing its assistance through the contribution of both resources and collaboration (especially in the IPM and EPA Pesticide Environmental Stewardship Programs). The purpose of PERC is to promote the safe, efficient use of propane as a preferred energy source. With the enactment of the Propane Education and Research Act in 1996, PERC began receiving funding by an assessment or "check-off" on each gallon of odorized propane gas sold in the U.S. Each dollar of the collected assessment funding is used to fund innovative programs and projects such as the thermal crop cultivation effort. Through PERC, the propane industry has committed itself to a multi-year, multi-million dollar effort to improve consumer and employee safety, to fund research and development of new and more efficient propane equipment, and to expand public awareness of propane and its many uses and environmental advantages.

Literature Cited

Timetable

Major Participants

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