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        Finding a herbicide that effectively kills a specific weed in row crops is easier than it was 10 years ago.  New products and technologies are available that eliminate almost any weed problem in peanut, cotton, corn, and soybean.  Alabama farmers have more herbicide choices than ever before.  However, the continued development of new herbicidal compounds by industry, combined with newly found uses for older materials, can make decisions difficult for prudent farmers.  AAES research shows that a new computer program named HADSS can aid in the decision-making process.

            HADSS is an acronym for Herbicide Application Decision Support System, which is a Windows-based program designed to aid growers, consultants, extension agents, and custom applicators in making sound economic decisions regarding weed control.  A primary goal of HADSS is to allow users to objectively compare the economic impact of alternative weed management strategies.

            Without the use of a decision aid such as HADSS, it can be extremely difficult to determine if a weed population is high enough to require treatment, and even more difficult to determine the economic benefit of any given treatment.  Herbicide prices have increased significantly, especially among the newer herbicides, which are popular because of their broad spectrum of activity against weeds, low usage rates, and environmental friendliness.  These new herbicides often cost  $20 or more per acre plus application costs (equipment and fuel), while many older herbicides that are still available cost much less ($4-$10 per acre).  HADSS helps producers select weed control measures that kill weeds and are cost effective.  HADSS functions also as a planning and teaching tool through which users may enter several weed scenarios and determine the best course of action.

            HADSS originated from HERB, a DOS-based computer program designed in the 1980s to evaluate weed control options for soybeans.  HERB was based on several assumptions.  First, different weeds compete with a certain crop at different levels.  Therefore, a competitive index (CI) must be assigned to each weed for a given crop.  For example, a carpetweed plant competes minimally with a cotton plant, but a cocklebur plant is perhaps the most competitive weed with cotton.  Given a scale of 1-10, with 1 being not too competitive and 10 being extremely competitive, carpetweed might only be assigned a 1 or 2, whereas the cocklebur would be a 9.5 or 10.

            Second, a treatment (a single herbicide or tank-mix combination) has a certain effectiveness for a given weed.  Therefore, treatment efficacy (TE) values may be assigned to each weed.  A given weed will have three TE values for each possible treatment; one each for small, medium, and large sizes.

            Finally, a mathematical equation can be derived for a given crop that relates the CI, TE, weed density, treatment cost, and yield potential.  The result of this equation is an estimated benefit (in dollars) of making a particular herbicide application.  HADSS, like HERB, provides a platform whereby multiple treatments can be compared on this basis, so that users can identify those treatments that will give the greatest economic return per dollar spent on herbicides.

            HADSS is the combined effort among several groups.  North Carolina State University (NCSU) first developed the HERB program and continues to develop and update the software program that runs HADSS.  NCSU also developed a database editor program, which allows individual states to customize a HADSS database to meet their specific needs.  Weed scientists at Auburn University and the Alabama Cooperative Extension System, as well as other agricultural colleges throughout the Southeast, are creating and maintaining databases for HADSS in their respective states.  Other states actively involved include Georgia, Louisiana, Mississippi, Tennessee, and Texas. 

            The database that drives HADSS is large and encompasses more than 500 weeds, 10 crops, and a huge number of possible treatments.  Therefore, research in Alabama has focused on reducing the database size to make it manageable and more applicable for use in Alabama’s major row crops: cotton and peanut.  Information that AAES researchers are incorporating into the Alabama database includes the following: (1) a local weed list including about 50 weeds that account for 80 to 90% of weed problems in Alabama; (2) adjusted CI values for those weeds; (3) approved treatments and TE values for each weed; (4) special warnings or restrictions on use; and (5) cost of each treatment.   A massive amount of data must be submitted to the database; therefore, weed scientists in many of the aforementioned states share information when possible and appropriate.

            To use HADSS, the user enters the following information: crop, variety (cotton only), estimated selling price, expected weed-free yield, rotation crop, weed species height and density, and crop height or growth stage (Figure 1).  In return, HADSS provides a list of treatment options based on net return to the producer (Figure 2).  From this list, a treatment may be selected and HADSS gives details of control, how much material will be needed, and also shows warnings or restrictions on usage.  HADSS also provides internet links to product labels and MSDS sheets.  It is important to realize that HADSS is a decision-aid and not a decision-maker.  Its recommendations should be viewed in light of individual experiences and situations. 

            In addition to maintaining the Alabama HADSS database, AAES researchers conducted field trials for several years validating the database to ensure its accuracy and effectiveness.  Cotton trials were conducted at the E.V. Smith Research Center’s Field Crops Unit near Shorter during 1999 and 2000.  Preliminary results indicate the HADSS program worked well and yields were equivalent to those plots that used standard weed control programs (see the table).  In 2000, peanuts were added to the database and field trials were conducted at the Wiregrass Research and Extension Center in Headland.  Plots utilizing the HADSS program for weed control produced the highest yields, equivalent to weed-free check plots (see table).  Also in 2000, the Alabama HADSS program was tested on-farm in Henry County, Alabama, with favorable results in Roundup Ready cotton.  These field trials provided key insight into the use of HADSS in Alabama and provided the answers to many questions. 

            The HADSS program with the Alabama database for cotton and peanut should be available for the 2002 growing season.  The database will be for postemergence use only and will be a desktop PC version.  Pocket HERB, a handheld version, and WebHADSS, an interactive Web version, are still in development for Alabama, but are available in other states.  In the future, more crops will be added as well as preplant and pre-emergence options.  Other possibilities include season-long weed management planning with HADSS.   

            For more information about HADSS, or to give WebHADSS a free try, visit the website at www.hadss.com. 

Faircloth is Graduate Research Associate and Patterson is Professor of Agronomy and Soils.

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