What is the TPDDL? 

The Texas Plant Disease Diagnostic Laboratory (TPDDL) is a service to the people of Texas by the Department of Plant Pathology and Microbiology at Texas A&M University, in conjunction with the Texas AgriLife Extension Service.    

What are the hours and location of the TPDDL?  

The TPDDL is open from 8:00 am – 5:00 pm, closed 12:00 pm – 1:00pm.
Walk-in hours: 9:00 am – 4:00 pm, closed 12:00 pm – 1:00pm.
The TPDDL is located at 1500 Research Parkway, Suite 130A, College Station, TX 77845. 

What kind of testing can the TPDDL perform?  

The TPDDL can assist with any type of  plant disease problem. Field crops, trees, turfgrass, vegetables, fruits, flowers, shrubs, houseplants, or any other type of plant is welcome. Lab tests are available for the detection of most plant pathogens. We can only test soil for nematode detection. For testing of most diseases of Upper Plains field crops, please contact the THPPDDL. 

* For palm phytoplasma detection, please see following document for sampling guidance.Sampling Guide for Palm Phytoplasma 

For nematode detection assay, see form D-827: http://plantclinic.tamu.edu/forms/d827/   

For commercial grape growers, see form D-1004: http://plantclinic.tamu.edu/forms/d1004/   

What parts of my plant should I send?  Check out one of these videos: 

How much does it cost to test my plant for disease?  

Please visit our Fees tab for more details about billing and cost: https://plantclinic.tamu.edu/fees/

How do I send my sample for testing?  

Samples can be submitted via courier, mail (preferably no more than 3-day delivery), or walk-in.
Walk-in hours: 9:00 am – 4:00 pm, closed 12:00 pm – 1:00 pm.
The TPDDL is located at 1500 Research Parkway, Suite 130A, College Station, TX 77845. 

How do I pay for my sample?  

Since September 2021, we have utilized the current billing system that requires all new clients to fill out form AG-257 (link to form here).  The department contact is ‘Texas Plant Disease Diagnostic Lab’, and the department contact email is ‘plantclinic@tamu.edu’. This should only occur once to set up a customer no. with Texas A&M AgriLife Extension Service. If you have used other AgriLife Extension services, you may have completed this prior – please include your customer no. on the TPDDL form when submitting samples. Completion of form AG-257 is required to extend our ability to process your sample with the necessary procedures for confirmatory diagnosis. 

We can no longer bill customers without completion of the AG-257 form. If a check is sent with your sample, then you will not need to fill out the AG-247 form and will not be billed after your report has been sent. We CANNOT begin any work on your submitted sample until we have a customer number in our system. 

If you are a homeowner and/or do not want to provide your identity information (SSN (Social Security Number)) on the AG-257, you can send a check in with your sample (pre-pay).  Please note that we can only conduct an analysis of the specific paid service that is requested and will not be able to pursue further analysis if needed for a confirmatory diagnosis. 

Checks should be made out to Texas AgriLife Extension Service (in blue or black ink only). Please put the check and form(s) in the box along with the sample. 

When should I expect to receive my report?  

Turnaround time is dependent on the specimen load received at the TPDDL. At peak time (spring through fall), routine diagnoses are usually finished in 11-21 days, depending on the test needed for the diagnosis. Specimens requiring extensive testing require more time. For example, oak wilt testing takes a minimum of 21 days. Diagnostic results are routinely emailed to the client, but results can also be mailed. 

Please contact us by email IF you have received an invoice but not the report OR have not heard anything 15 business days (3 weeks) after submission of the sample(s). We have instituted an email receipt reply notification to inform the submitter when we receive their sample and to provide a sample reference number for future inquiries related to that sample. Please make sure to check your junk mailbox.  

What if I need testing not listed on the website? 

For specific tests that do not have a specified form, please use FORM D1178 – General Diagnostic Service Form and note the requested test in the SPECIFIC TEST REQUEST (bottom right corner of the form) area.  Specific requested testing may incur additional charges. Please contact the TPDDL at plantclinic@tamu.edu if there is a need for specific testing of plant material for plant disease problems. 

If my plant is completely dead, can I still send it in for testing?  

Dead plants may be overrun with saprophytes or secondary pathogens, making diagnosis difficult and leading to inaccurate results. Accurate disease identification, diagnosis, and management recommendations are dependent upon appropriate specimens and thorough background information. A good sample is taken from the transition zone between healthy and symptomatic material.

How do I send an oak wilt sample?  

The accuracy of the laboratory assay is contingent upon the quality of the specimen submitted. Tissue that is too small, of the wrong type, desiccated, necrotic, or dead may contain too little viable vascular tissue or be contaminated with pathogens that will interfere with the isolation of the oak wilt fungus. Tissues selected from parts of the tree without good foliar symptoms may not be infected or sufficiently infected to produce a positive assay result. The current turnaround time for Oak Wilt is a minimum of 3 weeks due to the amount of time the fungus needs to grow on specialized media.  

OAK WILT or DED (Dutch Elm Disease) sampling:  

  1. Collect branches 1½ inches to 2 inches in diameter showing symptomatic leaves.  
  2. When possible, enclose twigs with symptomatic leaves still attached in a separate plastic bag.  
  3. Place the plastic bags in a Styrofoam ice chest with ice packs—DO NOT SEND ON DRY ICE OR WITH ICE IN PLASTIC BAGS.  
  4. Ship samples by overnight delivery to help ensure an accurate diagnosis.   
  5. Complete the Plant Disease Diagnostic Form (D-1178). We encourage you to include recent pesticide history (last 3 weeks) and any other pertinent information.  Please put the check and form(s) in the box along with the sample.   
  6. Ensure the identification on the form matches the labels on the sample bags.  
  7. Keep the completed form in a separate plastic bag from the specimen. Limit 1 (one) sample per form. 
  8. Package all specimens securely to prevent damage during transit. Cardboard boxes usually help prevent crushing. Add packing material such as newspaper to prevent specimen damage during shipment.   
  9. Ship samples to the above address by overnight delivery or mail early in the week to ensure fast delivery. Plant samples often decompose if left over the weekend in a delivery warehouse. Same-day or next-day service is recommended.   
  10. Obtain one of the submission forms (D1178) from our website, complete it, and send it in with your sample.  

Oak Wilt Sampling video 

How do I send a turfgrass sample?  

  • Take a sample from the area where symptoms progress/transition and send it in with our general disease diagnosis form (D1178). 
  • We care more about the plant material (leaves, stolons, runners, & roots) vs the soil or dead tissue. 
  • You can take a sample when it is dry or wet but it should be placed in a Ziplock bag to ensure that the sample is not soaked or compromised by an extensive amount of moisture. 
  • Our fee for Turfgrass diagnostics is $35/sample. If you want a diagnostic report for different areas of your yard, each will incur another $35 charge, and we will note whatever reference you use on the report. Please put the check and form(s) in the box along with the sample. 
  • Grass Sampling video 

Please contact TPDDL for any additional information at plantclinic@tamu.edu or 979-321-5390.  
Be sure to check us out on Instagram, Facebook, and YouTube: @txplantclinic   

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