How NOT to Submit Plant Samples for Diagnosis

When the most beloved landscape or garden plant begins to show symptoms of a problem, or commercial crops start to decline, panic may set in. The two things on everyone’s mind: what is the cause of the problem and what can be done about it? Since disease is often the prime suspect, the first step for many homeowners and growers is to contact the county Extension office. An agent may then assist in preparing a sample to submit to a University of Kentucky Plant Disease Diagnostic Laboratory.

Selection and packaging of a sample sounds like a straightforward and easy concept…put part of the affected plant in a box or envelope and send it away, right? Wrong! Sample quality and care in packaging can make the difference between receiving a rapid diagnostic report and receiving one of those dreaded “insufficient sample” replies. Avoiding common sample submission errors can result in more timely and accurate diagnoses.

Common Sample Submission Errors

1. Avoid packaging fruit or vegetable samples in sealed plastic bags, which promote decay; no diagnosis can be determined from rotted material (Figure 1). Wrap fruit or vegetables in several layers of newspaper and with extra padding to avoid damage during shipping (Figure 2).

Figure 1: Spaghetti squash packaged in plastic bags decayed during shipping and cannot be diagnosed. (Photo: Brenda Kennedy, UK)

Figure 1: Spaghetti squash packaged in plastic bags decayed during shipping and cannot be diagnosed. (Photo: Brenda Kennedy, UK)

Figure 2: Fruit and vegetables should be packaged in several layers of newspaper. (Photo: Julie Beale, UK)

Figure 2: Fruit and vegetables should be packaged in several layers of newspaper. (Photo: Julie Beale, UK)

 

2. Samples submitted with little or no packing material are often further damaged during shipping (Figure 3). Differentiation between symptoms and shipping damage can complicate diagnosis. Wrap rootballs in a plastic bag, leaving leaves and stems exposed; this also keeps foliage from becoming contaminated with soil from the rootball.  Use an appropriate sized box that can be padded and secured (Figure 4).

Figure 3: Samples with no packaging often suffer damage during shipping, resulting in complications with diagnosis. (Photo: Nicole Ward Gauthier, UK)

Figure 3: Samples with no packaging often suffer damage during shipping, resulting in complications with diagnosis. (Photo: Nicole Ward Gauthier, UK)

Figure 4: Samples should include additional padding to prevent damage from shipping. Roots and soil should be wrapped in a plastic bag to prevent damage. (Photo: Nicole Ward Gauthier, UK)

Figure 4: Samples should include additional padding to prevent damage from shipping. Roots and soil should be wrapped in a plastic bag to prevent damage. (Photo: Nicole Ward Gauthier, UK)

 

3. Dead is too late. Samples that contain only dead material are often impossible to accurately diagnose (Figure 5). Once a plant has died, secondary pathogens and other organisms invade tissues, complicating diagnosis and making it difficult to isolate the primary pathogen. The best samples include dead, dying, and healthy plant tissues (Figure 6).

Figure 5: Samples that contain only dead material reduce the chances of an accurate diagnosis. (Photo: Nicole Ward Gauthier, UK)

Figure 5: Samples that contain only dead material reduce the chances of an accurate diagnosis. (Photo: Nicole Ward Gauthier, UK)

Figure 6: The best samples include dead, dying, and healthy plant tissues. (Photo: John Strang, UK / Modified by Kim Leonberger, UK)

Figure 6: The best samples include dead, dying, and healthy plant tissues. (Photo: John Strang, UK / Modified by Kim Leonberger, UK)

 

4. Providing insufficient information can also hinder a diagnosis. Details about the plant, planting site, and symptoms can be as important as the physical material collected.  Provide as much information as possible on the diagnostic forms submitted with samples (Figure 7).

Figure 7: The sample submission form (left) and subsequent form for tree and shrub samples (right), should be filled out with as much information as possible. (Photo: UK Plant Disease Diagnostic Laboratories)

Figure 7: The sample submission form (left) and subsequent form for tree and shrub samples (right), should be filled out with as much information as possible. (Photo: UK Plant Disease Diagnostic Laboratories)

Additional Information

  • Submitting Plant Specimens for Disease Diagnosis (PPFS-GEN-09)
  • Plant Pathology Publications (Website)

 

By Kimberly Leonberger, Extension Associate; Julie Beale, Diagnostician; Brenda Kennedy, Diagnostician; and Nicole Ward Gauthier, Extension Plant Pathologist

 

 

Posted in Plant Disease Diagnostic Lab