Sample Collection for Disease Diagnosis
When sampling a block with disease, it is recommended to test multiple plants
showing several stages of symptoms, from mild to severe, as well as some plants
that are symptom-less but in proximity (see next figure).
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For each plant, collect several appropriate plant tissue (for example, 5-10 leaves,
leaves, twigs or spurs) showing symptoms and located in transition zones between
healthy and diseased plant areas. Collect them preferably using a large zip-lock
freezer bag (turned inside out, worn as a glove), one bag per plant. Follow a
sampling scheme starting from a remote healthy looking plant (the ‘Reference’ in
the submission form), to suspect plants neighboring diseased ones, and lastly the
severely diseased.
Bear in mind that foliar symptoms (chlorosis, leaf drop, wilt) can be due to trunk or
root rot. If in doubt, these woody tissues could be separately sampled and bagged
for testing.
Do not send dead tissue or samples derived from dead plants, already
decomposed by secondary pathogens.
For routine monitoring and early disease detection in a block, one of the following
schemes can be followed.
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