Picture of the Week

January 12, 2021​

The Purdue Plant and Pest Diagnostic Lab - Ready to Serve You 

Tom Creswell, PPDL Director, Purdue University

The Purdue University Plant and Pest Diagnostic Laboratory (PPDL) specializes in the identification of plant diseases, insects and plants, as well as in the diagnosis of plant-health related problems. The PPDL is a partner in the national Plant Diagnostic Network (http://www.npdn.org), a national consortium of diagnostic laboratories dedicated to enhancing the work of diagnostic labs through professional development.

We work to solving your plant problems with rapid and accurate diagnoses and identifications, including:

  • Fungal, bacterial and viral plant diseases
  • Insects and other arthropods
  • Unknown plants
  • Vertebrate pests
  • Environmental or cultural injury to plants

We serve as a source of unbiased information regarding pest management strategies and provide training for diagnosis of plant and pest related problems.

Sample handling fees for routine diagnosis: $11 for Indiana samples and $22 for samples originating outside of Indiana.  An additional $25 fee is charged for ELISA or Immunostrip (virus) testing. Tests requiring molecular (PCR) work are typically $25-75. Commercial Turf samples also have an extra charge. For more information on our fees and services and to download forms see our website at: 


Click image to enlarge


Impatiens Downy Mildew caused by Plasmopora obducens Impatiens Downy Mildew caused by Plasmopora obducens
rose stem Rose with Botrytis Canker
begonia with insv Begonia with symptoms of Impatiens Necrotic Ringspot Virus (INSV)
Ten Tips for Collecting and Submitting Samples:

1. Time is money: Don't wait until the problem is widespread to send a sample. Many diseases and insects are manageable if caught early.

2. Dead plants tell no tales: Plants which are totally dead, dry or rotten are useless for diagnosis. Collect samples from declining plants but not completely dead ones.

3. What's bugging you? For insect ID collect several examples, just in case some are damaged, or if both males and females are needed. Most small insects can be shipped in vials with 70% alcohol. For more details on how to send other insects visit our Physical Submission page.

4. More is better: The main concern may be overlooked if you send only one plant, one insect or a single branch. Send plenty of material, including whole plants when practical. Make sure samples are representative of what you are seeing.

5. Get to the root of the problem: Many plant problems are related to the roots and soil. For annuals and perennials in the landscape where the whole plant appears to be dying please dig up the entire plant to submit, rather than pulling them up. This will keep roots intact. For plants that are not removed please include a sample of the smallest diameter roots and at least a cup of soil. For problem plants in containers or plug trays, if possible, submit entire pots and plug trays to help maintain the integrity of the plants. We provide pH and EC readings of most soil samples submitted with a plant but for complete soil nutrient analysis you'll need a commercial lab.

(Email us at ppdl-samples@purdue.edu to request a list of labs in the region)

6. A place for everything: If soil gets on the leaves during shipment it can mask symptoms or even create a "disease" that wasn't there when the sample was collected. Keep soil around roots so they don't dry out. Bag the roots and soil and tie at the main stem or secure roots and soil within a double layer of heavy-duty aluminum foil. Wrap foliage in newspaper lightly then place a plastic bag over the rest of the plant and tie the top to keep foliage from drying out. Make sure foliage is dry before packaging.

7. The devil is in the details: The more you tell the diagnostic lab about the situation the better. Please give complete information; including name of plant, location, percent affected, symptoms of concern, distribution, soil type and drainage; and fertilizers or pesticides used recently. For Plant or Weed ID please give full details requested on submission form.

8. Fresher is better: Mail or deliver samples as soon as you can. Store samples in a cooler on hot days until you can deliver or ship them. Avoid mailing samples late in the week since most plants will start to rot after being in transit over a weekend. A next day delivery service is needed for urgent samples or those that may rot quickly in shipment.

9. Fragile, handle with care: Padded mailing envelopes may be used for samples that are not fragile, such as ears of corn, but sturdy cardboard boxes with crumpled newspaper for padding are preferred in most cases (essential for young and tender plant material). Insect vials must be padded to prevent breakage in shipment.


Click image to enlarge
poor packaging Dig plants and contain soil and roots in plastic bag secured around base of stem.
good packing Packaging of plants in pots.

10. A picture is worth a thousand words: Photos are very helpful for Plant ID and Weed ID and critically important for diagnosis of tree, shrub and turf problems. See our guides for taking good photos of trees and turf and find links to our photo upload tools at our Photo Upload page. Photos can also be emailed to ppdl-samples@purdue.edu. We prefer you not send print photos unless they have been printed on a photo printer or at a store kiosk. The sample handling fee covers working with both photos and a physical sample. 

Critical sample on the way?: Email us at ppdl-samples@purdue.edu to let us know you are planning on sending samples that may require special handling. 

Our shipping address: 
Plant and Pest Diagnostic Lab
Purdue University
915 Mitch Daniels Blvd, LSPS Room 116
West Lafayette IN  47907-2054

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