Grit barrier against fungus gnats?

[glossterline]

Often the problem of fungus gnats (and other small flies associated with orchid compost) is raised in this forum, and I have just seen it raised in relation to other house plants (Africal violets in fact).
The 'experts' suggested that 1/2 inch of grit on the surface of the soil prevented the flies from laying their eggs in the compost. I wondered whether this is of any use to orchid growers?

Les

[benetay]

Interesting concept! I really like to hear from the rest too.

Actually tobacco juice helps prevent them too.

Cheers!

[janet_a]

i'd think that the grit would just sift thru the medium, depending on how coarse it is.

i've had one of these follow me to work today.

[glossterline]

Hi Benetay! Does that mean that you chew on a plug of 'baccy' and spit on the plants?
Les

[digitalgate]

nah, you take some tobacco leaves(one table spoon) , soak in 100c water . let it cool down and dilute about a gallon and spray everything.
I don't like it. The ants i spray did not die. But the whole lot disappear after 2 days. strange! May be useful after all. For orchid grown in cold and humid environment cover the media will lead to fungus problem. So use a harmless Pyrethroid will kill them .

[janet_a]

*however*, and this may be an old wives' tale, you need to be cautious about transmitting tobacco mosaic virus to your plants.....

[digitalgate]

Originally Posted by janet_a

*however*, and this may be an old wives' tale, you need to be cautious about transmitting tobacco mosaic virus to your plants.....

virus will be dead in a 100c (degree Celsius-boiling water)

[janet_a]

ah.






_________

[Ray]

Sorry, but that's just not true. There are many bacteria and viruses that can survive 100°C.

Most autoclaves boost the temperature to at least 120°C (about 250°F), and there are bacteria that thrive in volcanic- and undersea vents, where the temperatures are a lot higher.

[missann]

I too, have heard that the eggs cannot survive in sand/ grit because they dry up and die. However, that is not something I would reccommend putting into orchid pots because it would just fall down into the bottom of the pot.

In my research, I found THE BEST FUNGUS GNAT ELIMINATOR!!!
BT or, bacillus thuringiensis israelensis
This is a bacteria used for killing mosquito larve in bird baths, ponds, etc. It comes in granular form as well as doughnut shaped "dunks." I was unable to find the granular form, so I bought some dunks at wal-mart, took off a chunk, (maybe 1/8th) and put it into a 2 gallon jug of distilled water overnight. (tap water contains cholorine and can kill the bacteria) Stir Then I just water my plants with this for a few days and it kills all the larve from the fungus gnats. It's safe to use indoors, and I found it to be much more effective than bug sprays. If you have any questions, please just send me a PM.

[patticake]

Interesting....

[Ron]

Hi,
I have found most times fungis gnats etc come around in the mix is because it is going sour. usually just a light dusting with common garden lime & water in, will change the PH and the bugs/gnats will look for a new home, works for me.
Dose of Pyrithium will do nearly a good job but they will come back because of the low PH.
good growing
Ron