New Commercial System

[GaryD]

Hi Paul,

I believe that it has been shut down........in the short term at least.

It appears that leaves from eucalyptus trees adjacent to the site were falling into the grow troughs. The operator believes that an infusion from the gum leaves may have been inhibiting the growth of the lettuce.

He's currently considering his options.

Gary

[Crusty]

Hi Paul,

I believe that it has been shut down........in the short term at least.

It appears that leaves from eucalyptus trees adjacent to the site were falling into the grow troughs. The operator believes that an infusion from the gum leaves may have been inhibiting the growth of the lettuce.

He's currently considering his options.

Gary

Hi Gary, thanks for the update. Absolutely fascinating but a shame. Something all Australians should consider, gum trees...

[GaryD]

Hi,

I've been aware, for a long time, that some gum species inhibit the growth of other shrubs and grasses, but I would probably have made the same mistake in the same situation.

I had a situation where toxic plant substances impacted one of my systems......but, rather than affect the plants, it killed fish.

We have a silky oak in the yard next door and wind-borne debris from the tree blew onto our tanks.....and made its way into one of them.

The fish tank contained some very healthy barramundi which started to die slowly for the first day or two......and then very quickly.

I tried everything.......water tests, aeration, salting, modest water changes.....all to no avail. The fish did not exhibit any obvious disease symptoms.

In sheer desperation, I started moving the fish into the tank alongside.....and they began to recover immediately. Fish that had been swimming upside down, and on their side, righted themselves and began to exhibit normal behaviour.

I noticed some twigs and foliage in the tank and identified them as belonging to the silky oak.

We drained the system, refilled it and transferred a few fish into it while we confirmed the cause of the problem. They behaved as they do usually......and life returned to normal.

While I couldn't swear that the silky oak leaves were the cause, given everything that happened, that's where my money is.

Gary

[Crusty]

Interesting thoughts. Have you contacted a fish vet. to confirm silky oaks toxicity to fish? That is where I would put my money.

[GaryD]

Hi Paul,

I grow fish and vegetables as clean fresh food.

That precludes spending large sums of money on vets......a judgment call that most small farmers have to make when confronted with the odd incident.

Given the circumstances that I've described, toxicity is the most likely explanation. Which exact substance it was, and how it got there, is now entirely academic.

Had I been a commercial grower things might have been very different.

Gary

[Crusty]

That is a shame it would have been interesting to know for sure.

Hi Paul,

I grow fish and vegetables as clean fresh food.

That precludes spending large sums of money on vets......a judgment call that most small farmers have to make when confronted with the odd incident.

Given the circumstances that I've described, toxicity is the most likely explanation. Which exact substance it was, and how it got there, is now entirely academic.

Had I been a commercial grower things might have been very different.

Gary

[Crusty]

I took the liberty of looking into this a little more to satisfy my curiosity.

The flowers and fruits of silky oak contain some hydrocyanic acid (hydrogen cyanide) the remainder of the tree, leaves etc. do not contain any. Below is some reference for the toxicity of hydrogen cyanide to some fish species.

http://www.pesticideinfo.org/List_Aq...axa_Group=Fish

Here is also a reasonably complete list of plants in AU that have been recorded to have toxic effect.

http://www.alpaca.asn.au/docs/about/...son_plants.pdf

I have emailed our fish vet. to see if he has anything related to the silky oak and barra. Will let you know what he thinks.

[GaryD]

Thanks for that. This far down the track, I can't be sure if there were seeds and flowers in the tank.....it all happened pretty quickly.

Gary