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The Good, The Bad, and The Ugly
Good samples for isolation With infected tissue (water-soaked, dark brown lesions) Fresh & wet leaves Bad samples Disintegrated leaves (exposed too long? strong activities by other microbes?) Dried leaves Muddy leaves (may have soil isolates) Ugly samples Completely healthy leaves (Phytophthora free/low density? need longer exposure? need more susceptible baits?)
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Big vs Small Small leaves may not provide enough leaf material for good diagnostics.
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Dry vs Wet Keep bait leaves cool and moist from the time they are collected from plants and deployed in streams; and from the time they are retrieved from streams and shipped to the diagnostic labs.
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Same State, Different Results
There can be considerable variation in symptom development among leaves in a single bait bag; in leaves deployed at different time periods in the same stream; and in leaves deployed in different streams in the same state.
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The Good Lots of good transition between apparently healthy leaf tissue and lesions for isolation.
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The Bad Too far gone… too long exposure time?
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And The Ugly No symptoms… too short exposure time.
If these must be collected, always attempt to isolate from the petiole, even if not symptoms appear on the leaf blade itself.
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Do not wait too long!!! Don’t wait for hell to freeze over before collecting bait leaves.
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