Utah Pest News Fall 2010

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Proper Submission of Samples for Disease Diagnosis

samples
The two branches on the left are examples of samples that are not useful for diagnoses.  The far left branch is too dry, making it impossible to isolate a living pathogen from the tissue.  The middle branch is also dry, and has no leaves.  The branch on the right is freshly cut, allowing us to isolate and identify the causal agent. 

 
There are many causes of plant diseases including biotic (fungi, bacteria, viruses, nematodes etc), abiotic (temperature, frost, irrigation, pesticides, herbicides, etc.), or a combination of both.  To efficiently diagnose a diseased plant, it is important that the Utah Plant Pest Diagnostic Lab (UPPDL) receives a proper sample and detailed information about the situation.

SAMPLE SUBMISSION EXAMPLES

1.    Tree with dieback of some shoots or branches:  Send at least two symptomatic shoots (if possible cut them off where the shoot is still green) and two healthy looking shoots.  It is OK to cut a shoot in half to fit in a Ziploc bag.  For conifers, collect two branches that have both green healthy needles and symptomatic needles.

2.    Wilting or dying tree:  Send as a slice of wood or, for smaller trees, a segment of a branch (no longer than 2 feet) as well as some roots.  The roots should at least be pencil-size.  Also, if you see any fungal fruiting bodies (such as a conk on the stem, shown below, or mushrooms at the base), include them with your sample.

conk annosus

3.    Vegetables or non-woody ornamentals:  Send the entire plant (if less than 2 ft in size), or parts that include leaves, roots, and shoots.

4.    Turf grass:  Cut a segment from your lawn where the problem occurs (about 4 x 4 inches) including roots, shoots, and soil.  Cut an additional segment from an area where the grass looks healthy.

SAMPLE COLLECTION and PREPARATION

Collect the samples either the same day or the day before you plan to mail or hand-deliver them to the UPPDL or county extension office.  Place samples in a Ziploc bag without a moist paper towel, and keep them refrigerated until they are ready to be shipped.  The Ziploc bag will keep the sample moist enough on its own, preventing it from drying out.  Samples that have dried out or that have been stored in the refrigerator for days or weeks before they are sent make it impossible for us to identify the cause of the problem.

Overnight delivery of all plant disease samples is best.  If you collect a sample on a Friday (and are not hand-delivering it), keep it in the refrigerator and wait until Monday to mail it so that we can receive and process it before mold and other microorganisms grow on the sample and inhibit diagnosis.

SAMPLE INFORMATION

All samples should include a completed UPPDL sample information form, which can be found on our website (click here).  You can fill it out online and then print it out.  The more information you can provide us with, the better, including location, plant age, fertilizer and pesticide applications, and irrigation.  This information will help us narrow down the possible causes of the symptoms.  Information on the location (city) allows us to determine if weather such as an early frost could have caused the symptoms.

PHOTOS

Providing photos of the symptomatic plant, both close-ups and more distant images, helps us to determine the problem. This is especially important when environmental factors such as pavement or salt application in the winter could be behind the problem.  You can either email the images or include prints when shipping the sample.

Proper sample submission gives you and us the best chance to identify the cause of the problem.

NOTE:  Please do not send soil as we cannot test soil for mold or fungi.

-Claudia Nischwitz, Extension Plant Pathologist