A Few Considerations
 
Sample should be representative of the problem in the field.
Sample should be fresh/recently infected.
Sample should be adequate in size.  How large?
Never collect dead plant samples!
   
For leaf spot problem, usually about 20 leaves are adequate for the diagnosis procedures (microscopy, culture work, etc.)
Large leaves with many spots will require fewer leaves for diagnosis than small leaves with fewer spots
   
Whole plants are generally needed for all problems that are not leaf spots (e.g. wilt/blight problems)
   
Dead plants tell no tales!
   
Avoid plants that are obviously dead. Select plants that exhibit a range of symptoms, from mild to severe.
 
Useful materials/tools during sample collection:   Essential Guidelines
 
 
 Wrap sample in clean and dry paper towels/newspaper.
 
 Do not add moisture!
 
 Place sample into a plastic bag to prevent desiccation.
 
 Sample must be kept fresh and in good condition.
 
 Samples to be mailed should be placed into a padded envelope or strong crush-proof box to prevent damage during transit.
 
 It is always best to mail a sample during the first part of the week, rather than late in the week when there is a risk that the sample will stay in transit for the weekend.
 
 Do not forget to fill-out the Disease Diagnosis Request Form!
     
An alternative way of sending virus-infected plant samples
 
Samples can be temporarily preserved using desiccants (calcium chloride/silica gel or beads)
 

 
References:
State Agricultural Response Team (SART), University of Florida

Windham Mark T. and Alan S. Windham. 2004. Plant Pathology Concepts and Laboratory Exercises. CRC Press, USA.