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fungus gnat yield penalty


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Leaves on my scogged single ak47 girl started yellowing and it turns out that the pot was absolutely infested with fungus gnat larvae. I noticed em ages ago but just tollerated them didnt seem to be causing harm were just eating fungus, it seems they then just exploded while i wasnt watching and started eating roots (i think)

Quick stats

- week 3 of flower

- recirculating hydro with plantastic flower nutes

- rock wool

- 1 x 600 hps

- used a pgr just before problem started - i hate pgr's but my house lease is nearly up and needed to finish this gurl early.

 

I have used neem for the maggots and confidor for the flys plus using a sticky trap for any more flies.

 

What i would like to know is how much will this affect my yield considering that i have lost a good 20-30% of my big fan leaves??

 

I know people on here have posted simular problems was yield seveerly affected?? - thats my question

 

Thanks in advance for anyones time

Edited by danoz
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danoz i know the fungal gnat .. unless you know for certain you have eradicated all lavae , and thats a big ask if you have a colony established, whats their life cycle / i forget off hand but its like 20 days or so ? they were at all stages too ..

plus unless you have totally restricted the gnats access to the plant they smell out the pots from a distance ...

dont underestimate the gnat he is a worthy opponent, look out a small % of your infestation drink neem and only come off grogy, they are resiliant terrorists of the insect kingdom ...

yea the lavae actually chew on the ends of tender young rootlets and in doing so deprive the plant of the ability to take up nutrients

so lets hope you have eliminated them and you might only be down 20-30% on harvest ..

 

best with 'em lol

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Pyrethrun is very hard on the plant, especially the foliage, not saying it doesn't work.

Scarid 10, non systemic, soak the whole pot for 5 mins, again in 7 days to kill the emerging larvae. It works too. Yield? depends how shagged the roots are. 3 weeks into flower, they will recover and finish but your harvest time is going to lengthen a little too as the flowers struggle to form.

I'd add a bit of Hydrogen Peroxide or Pythoff as the gnats self seed the Pythium spore which will cause root disease and your harvest will be even smaller.

As the roots die it attracts more adult gnats(sciarid fly) that's my reasoning with using the H202, to keep the food source as low as possible. The other plan of attack with gnats is to establish healthy bacteria in the rootzone first before Pythium can take over. Cannazyme is useful here as it breaks down the dead roots quickly.

It's no good wiping out the infestation if there is still food source available.

Hope that helps.

Edited by Hector
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thanks to all for the sharing your experience and advice.

 

flowers are stuggling to form. I transplanter her to a bigger pot and OMG the roots have been slaughted i think my yield will be low, my fault though i only check on her and fix the recirculating nutes up once a week (big reservior).

 

Thanks for the advice regarding the hydrogen peroxide in my own googling i herd this was a good idea after drenching for reasons x y z yuta yuta. Interestinly though, it sez that hydro perox also kills larvae??

 

anyway ill repost in how ever many weeks to report on how this seveer infestation effected yield. Such a shame too, she was a awesome plant i took clones off her lower stem, and trimmed the top, so she looked like a ornamental standard- like a standard lilly pilly with a pretty lolly pop stucture.

 

anyway put it down to experience

-by the way treatment as far has been - NEEM drench, pyrethrum for the adults, sticky trap for any that come along after, and plan to rinse with H2O2.

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Interestinly though, it sez that hydro perox also kills larvae??

 

Yes, that's correct, I think I have this doco'ed in an old coco diary here.

If this is your plan give em heaps, at least 10mls per litre for 12% H202, more if you've really got the shits, and hit em again in 7 days.

Use the H202 mix as soon as possible(first few hours) for maximum effect before the extra Oxygen molecule is given off in the water.

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NEEM completely reemed the little maggets 7 days ago. Today i was inspecting because a follow up dose was due, and oh goodness the little devils were back with avengence hopefully the follow up dose will break their life cycle. Added a high dose of H2O2 after the follow up NEEM dose to try and rinse some of the decaying organic material in the pot (organic matter not the friend of hydro systems)

 

Anyway what was a gunna by one very high yielding scrog plant is gunna just be a moderate low yielding plant, considering the amount of bloody leaves it lost its still doing ok. I have now lost a good 50% of the large fan leaves, the real producers. It would be interesting to see where radio labelled carbon would go in this plant. To the roots for regeneration or is the plant just gunning to finish flowering at the expense of the roots???? stress partitioning of photoassimulates is interesting stuff.

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SUMMARY HOW IT ALL WENT DOWN IN THE END

 

ok i harvested a couple weeks ago now.

 

Yield was centainly reduced its hard to say by how much.

 

ROOTS

Ok i noticed that when i transplanted the infected plant the root mass was completely brown, dead, and chewed by maggots. After three weeks maggot free i harvested and reinspected the root mass. roots showed strong signs of recovery with fresh white root tips shooting from almost all old dead roots. VERY surprising how resilient weed roots are.

 

 

TREATMENT

In end to completely rid my room of these fucking devil worshipping pricks required a three pronged approach.

 

KILL ADULT FLIES - insecticide

 

KILL FUTURE adults - sticky trap

 

KILL larvae with NEEM

 

PREVENTION IN THE FUTURE

However ultimately i prefer a intergrated pest management approach and therefore in the future ill aim for prevention instead to avoid all the nasty chemicals i used.

Prevention

-DONT let algae grow

-Use a sticky trap for monitoring

- Try to keep the surface of rockwool dry by irragating just under the surface

 

THE POTENTIAL ROLE OF PGR's

Another thing - i noticed that my problem only went critical after i applied a PGR. if u suspect you have some gnat larvae do not use pgr's.

Interestinly if you examine the roots of plants after pgr addition the change completely. they change from thin white healthy looking structures to very fat and slightly off white structures with fewer hairs.

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Thanks for the updates danoz , at first insects can appear innocuous, almost harmless until you ask them to move along, then they dig their heels in and it seems to be a huge battle as to who shall survive .. the insects or the plants ...

interesting observations on the pgr's too

 

:peace:

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