Consensus on Orthene for fungus knats a NO NO ? - Orchid Board

greenpassion · #1 06-02-2012, 02:10 PM

I have two newer orchids living with my other ones that have been in S/H for months now. I have noticed that I have fungus gnats flying around, and as I know S/H won't support their living requirements, they have to be from the new milts I received planted in bark and moss. In reading thru some posts in this forum, someone, (maybe Ray) suggested using Orthene to kill the larvae. In looking it up I came across (in a bromelaide discussion board) someone expounding on the dangers of using orthene on orchids other than phals and various thick leaved plants. If this is so, what would be an alternative to using orthene?

Gin · #2 06-02-2012, 10:52 PM

For gnats I have used the yellow sticky traps also the mosquito dunk treated water seems to get rid of them not seen any around for a long time . Gin

zxyqu · #3 06-02-2012, 11:06 PM

Agreed with Gin on this one. Use the traps to take care of those flying around (or if you have a greenhouse or enclosed space, I prefer carnivorous traps like drosera), and mosquito dunks for your water supply. Has really been working ever since my problem exploded. Almost completely gone now.

Ray · #4 06-03-2012, 07:46 AM

To answer the original question, I have never seen Orthene hurt any orchid.

It should be quite effective on fungus gnat adults, but I'd like to offer a couple of more things to consider:

The idea behind the sticky traps is to reduce the adult population, and the mosquito dunks infect the critters with bacillus thuringiensis v. israelensis, a natural way to eliminate them, but to me, their mere presence indicates that there is fungus growing in the medium, which means it's decomposing, so they are the "canary in the coal mine", warning you about a need to repot.

Susie11 · #5 06-03-2012, 10:46 AM

Humm, I have recently repotted and I am seeing alot of these things flying around. I don't over water my phals which is were they mainly are. They get it only when the roots are showing white and then it is poured through the top of the medium for a while. They don't sit in water and they don't appear to be soaking wet -evenly moist I would say so I don't see why they are so prolific. I hate them -I really do. They ruin an otherwise pleasant experience. Maybe I should get the traps too?

zxyqu · #6 06-03-2012, 10:54 AM

I really do appreciate Rays stance on this, but in my conditions, these little buggers occur independent of moss breakdown. I only use moss and S/H an the collection just turned over to new media and yet, I still have some of these moving around. All in all I have no idea where these buggers hideout. So I'd recommend treating both the adults and with the dunks, and to also stay on top of reporting just in case.

Susie11 · #7 06-03-2012, 11:17 AM

I have just googled fungus gnats and apparently there is a really good product available online called GnatOff or there is another one called Gnatrol. They work! They are pricey at £20 for 250ml but they work. I shall be buying some pronto.

Ray · #8 06-03-2012, 02:59 PM

Fungus gnat larvae live on fungi growing on decomposing organic matter, If that supply runs out or is outstripped by the population, they can inhabit the roots too, and that's where the real damage comes from.

No gnat is a good gnat.

greenpassion · #9 06-04-2012, 01:19 PM

I have to respond to Ray's post in this matter. I am convinced that it's more than likely that the gnats are from the two orchids that I just received that are planted in moss/bark. I want to repot them, but they are both currently blooming. I want to wait until they are finished, then put them into S/H. As far as the suggestion of tape to catch the adults, my orchids are a center piece in my living area. I grow them on an island under track lighting, and this divides my kitchen from my living room. The idea of nasty tape being seen is not something I'd want to do. I'm going to look for Orthene. Do they make it water soluble-as an additive to the water I'd use to flush and water them?

Susie11 · #10 06-04-2012, 02:01 PM

I am having the same problem at the moment. I can't move for seeing nasty little black flies buzzing around my orchids angrily whenever I am near them. I am going to get the fly paper for the time being until I can locate some Gnat Off which is supposed to be really good. I doubt that the product that you mentioned is available in the UK -nothing good ever is allowed into the country so it wil have to be that for now.