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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