"Paul M. Cook" wrote in message
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"Nelly Wensdow" wrote in message
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"Paul M. Cook" wrote in message
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Well the leaves continue to die at the crown although a couple very
deformed ones have managed to survive. What I discovered this morning
was the pot was crawling with tiny black flies. Must have been a
hundred or more. So I hosed it with pyretherin spray and that killed
them off quick. Could this damage be caused by a fly larvae?

Yes, fungus gnats. A thin layer of sand on the soil surface will
discourage flying adults from laying more eggs. Use some kind of Bt next
time you water (a dissolved mosquito dunk will work in a pinch) for
longer term control.

Turns out it was ZYMV - zucchini yellow mosaic virus. Took one of the
affected plants up to a good garden center with real gardeners running it
(not teenage kids) and the guy said it was mosaic virus. He advised
dumping the soil and scrubbing the container.

How serious is this? Is it totally contagious? Is it safe to reuse the
soil with some other non-cucurbit plant?

Paul

I didn't see the original post, but the fungus gnats got in there mostly
just because the soil was damp, which can come from either overwatering, or
from sick plants that don't have the capacity to take the water up anymore
(which sometimes comes from overwatering). Larvae can still munch on healthy
young rootlets after their more favored decaying matter is spent.
Not sure about this virus, but most can be killed by pasteurizing the soil.
Whether you do this or replace it, clean the pot & sterilize it. Pretty much
standard procedure for me anyway because it's just good hygiene, and
whenever pulling a pot out of storage I don't have to worry what condition
the last plant occupying it was in.