Alliance Bank in Sulphur Springs

Why and When of Using Herbicides


Mario Villarino DVM, Ph.D.
Hopkins County Extension Agent for Ag and NR

Timing in agriculture: the why and when of using herbicides

I often get questions related to herbicide use. According to the Texas Department of Agriculture, because of their potential to cause adverse effects to non-targeted vegetation, herbicide products containing selected active ingredients shall be classified as regulated herbicides when distributed in containers of a capacity larger than one quart for liquid material or two pounds for dry or solid material. If the products are marketed using metric measures, the classification applies to containers larger than one liter or one kilogram, respectively. A common use regulated herbicide compound in Texas is 2-4D. According to the National Pesticide Information Center from Oregon State University (, 2,4-D is a herbicide that kills plants by changing the way certain cells grow. 2,4-D comes in several chemical forms, including salts, esters, and an acid form. The toxicity of 2,4-D depends on its form. The form also affects what will happen to 2,4-D in the environment and what impacts it may have, especially on fish. 2,4-D is used in many products to control weeds, and it is often mixed with other herbicides in these products. 2,4-D was first used in the United States in the 1940s. Agent Orange, an herbicide used during the Vietnam War, contained both 2,4-D and 2,4,5-T. Dioxin, a by-product of 2,4,5-T, led to the ban of Agent Orange. Products containing 2,4-D may be liquids, dusts, or granules. The liquid forms may be concentrated or ready-to-use. There are over a thousand products with 2,4-D in them that are sold in the United States. 2,4-D kills broadleaf weeds but not most grasses. 2,4-D kills plants by causing the cells in the tissues that carry water and nutrients to divide and grow without stopping. Herbicides that act this way are called auxin-type herbicides. Because 2-4 D works in active growing plant tissue, the best control effects occur when the herbicide is applied during active plant growth. Plants during flowering are not growing anymore and the control effect of 2-4 D based products is reduced during this stage. The purchase of restricted pesticide is regulated by the Texas Department of Agriculture by licensing. Private farmers and ranchers can apply for license by becoming a private pesticide applicator. The steps to becoming a private pesticide applicator are:

Step1: Attend a Private Pesticide Applicator training session FIRST. The last private applicator training for 2015 will be October 30 2015 (Cost $30). Contact your county Texas A&M AgriLife Extension office in Hopkins County at 903-885-3443 to register. Texas A&M AgriLife Extension offers the Texas Private Applicator Training Course online also.

Step 2: Upon completion of the training, a Training Verification form (D-1411) will be provided to the applicant. Applicants should keep the yellow copy for their records. The white copy (original) should be mailed to TDA with the Private Pesticide Applicator license application form (PA-400P).

Step 3: The applicant needs to obtain a hard copy of the Private Pesticide Applicator license application form(PA-400P) from TDA. (Website: www.TexasAgriculture.govor  Phone: 1-800-835-5832 or 512-463-7622).

Step 4: Submit the completed Private Pesticide Applicator application form, license fee of $60, and the white (original) copy of the Training Verification form to TDA for processing.


Step 5: When the license application is accepted, TDA will send the applicant a letter in the mail with their Account Number. This Account Number is the number the applicator will use to register and schedule the Private applicator exam with PSI.


Step 6: Applicants can go to PSI or call 1-800-733-9267 to schedule an exam at one of 22 locations around the state. A Pesticide Licensing Examination Candidate Information Bulletin is provided at the PSI website to assist the applicant with the exam scheduling process. A private applicator exam is free for the first attempt. If the applicant fails the first attempt, the second (or subsequent) attempts will require a payment of $52.00 each time to PSI. There is a 24 hour waiting period to take a repeat exam. PSI will provide a confirmation number and testing location information. Step7: Upon completion of the exam, the center will provide test results immediately. A passing grade is 70%.


Step 8:  PSI will send exam scores to TDA daily. If all licensing criteria are met, TDA will issue the license. Important: If an applicant has any questions about licensing or categories, please contact TDA.

For more information on this or any other agricultural topic please contact the Hopkins County Extension Office at 903-885-3443 or email me at [email protected].

Author: Staff Reporter

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