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Adding top layer of sand - some concerns...

Capt Cannabis

Capt Cannabis

Member
Hey guys,

I have been battling pests for the first time during this grow, I believe they are fungus gnats. I have been using neem oil with no improvement. When the plants were younger I put a 1/2" layer of sand on the top of the soil on each plant and the bugs were gone within 48 hours. I was experiencing some issues with yellowing at the time, and I wanted to see what your experiences were when adding sand to your soil. The sand is not from the beach, from a local hardware store.

A few questions regaurding the use of sand:

1) What does sand do to the PH of my soil? Since the sand is on the top, the water and nutrients I give them go through the sand first. How does the top layer of sand affect the PH?

2) Should I do anything to the sand before using? It's coming from a huge pile outside the hardware store.

Any other issues or concerns I should be aware of?

Thanks very much,

The Captain
 
C

Cappy

Active member
diotomacious earth will do a great job at killing soil born pests that need air to reproduce. Sorry, don't know about sand....
 
B

budbasket

Member
Id be careful about adding in sand, if you don't get the ratios right you'll end up with a poor mans cement, not very good for root growth. Diatomaceous earth which has been mentioned previously, I think would do the job, it works by speeding up the insects evaporation levels and basically dries em out. I read also that it will kill larvae by cutting them as they pass almost like rubbing against shards of glass.

Pyrethum bombs and or gnatrol(Bacillus Thuringiensis bacteria) works as well, maybe could consider a rotation of different applications. You could also look into IPM(integrated pest management) beneficial nematodes as well as predatory mites are available however I have no idea if it they were meant for treatments in cannabis. Could end up trading one pest for another. Good luck!-basket
 
S

SeaMaiden

Sand works just fine, but what you want to do is determine whether or not it's calcareous, which will definitely change pH. Just take a small container of vinegar with you and pour some on the sand in question. If it bubbles, it's calcareous and will change pH. If not, you should be golden.

Use the sand.
 
Treetops

Treetops

Active member
Me too....So far no problems....makes the plant/pot heavy though, so get used to the new weight...:)
 
S

SeaMaiden

Play sand, which is typically Si-based anyway, can also provide some Si. So do rice hulls. I find DE gets washed down through the soil pretty quickly.

How about adding some yellow sticky traps to your decorating scheme?
 
S

SeaMaiden

I guess I can't delete this post. This has happened to me three times now, I hit 'submit' and then I get a message saying that this forum requires I wait between posts. I don't get clicky with it, I think it's some glitch, either in the browser, or....?

Anyway, double-post. Sorry! :tiphat:
 
Capt Cannabis

Capt Cannabis

Member
Wow guys posted about 3 hours ago and I come back and check on the thread, and there are 10 replies! Thats awesome, thanks.

It seems like DE has given a lot of good results. Where do I get something like that? Hardware store? Hydro shop only? What else is it used for, or only plants?

I know the sand will get rid of the bugs in no time. Just worried about adverse affects from the sand. Seems like others have had pretty good results using sand too.

Thanks again for all of the quick replies, I am really impressed. This community is priceless, all the members look out for each other and thats what its all about.

Will keep checking in,

The Captain
 
cyat

cyat

Active member
Veteran
none of that will work from my experience.
done the sand, d.e. powder, and 2 sizes of d.e stones, perlite, cedar,cinnamon, crabshell, topdressings. and bt didnt work for me either.
wanna find a natural remedy, still looking tho.
alternating with gonats, neem, and sm 90 now and its not really working

other stuff to try dryer sheets, potato slices, and pyretherin drench?

good luck
 
chief bigsmoke

chief bigsmoke

Active member
Capt Cannabis said:
Hey guys,

I have been battling pests for the first time during this grow, I believe they are fungus gnats. I have been using neem oil with no improvement. When the plants were younger I put a 1/2" layer of sand on the top of the soil on each plant and the bugs were gone within 48 hours. I was experiencing some issues with yellowing at the time, and I wanted to see what your experiences were when adding sand to your soil. The sand is not from the beach, from a local hardware store.

A few questions regaurding the use of sand:

1) What does sand do to the PH of my soil? Since the sand is on the top, the water and nutrients I give them go through the sand first. How does the top layer of sand affect the PH?

2) Should I do anything to the sand before using? It's coming from a huge pile outside the hardware store.

Any other issues or concerns I should be aware of?

Thanks very much,

The Captain
Click to expand...


My hort professor had some easy steps to help prevent fungus gnats and other soil-born critters.
1. Pour 2 inches of course sand - course so it cuts the soft bodies of the critters.
2. Finely crush some egg and oyster shells and top dress the soil with them - they act as a sharp defense barrier and also they contain up to 98% calcium carbonate so they are a great slow release source of calcium.
3. Then alwayys ALWAYS let your soil dry out in between waterings. gnats love the top couple inches of soil so you will cook their home. I always make sure that 3 inches of my soil is completely dry in between waterings.


I had a bad bag of SEA SOIL that had a ton of bugs. I used the sand technique to first combat the issue then I removed most of the sand and continued with the shells and the drying out of the soil in between waterings and I haven't had a large infection since.

I don't believe it would change the ph. But if left it has the chance to change your soil structure.

One of the best ways to battle them is to add lots of beneficial bacteria and fungi. There are also lots of beneficial predators like mini wasps the lay their eggs in the larvea etc.
 
C

Cappy

Active member
DE does have to be used properly to be effective.

I like to use it when I transplant because the soil gets a fresh watering and it takes awhile for the roots to fully expand into it and use up the moisture. Leaves much more time for the dry DE to be effective, in other words. 7-10 days in the case of plants in my room, plenty of time to kill pests off thoroughly.

Good luck!
 
señorsloth

señorsloth

Senior Member
Veteran
i would like to second everybody else who said use diatomatious earth, not sand, the microscopic razor sharp edges of the white dust abrade the exoskeletons of the fungus gnats and their larva, i have NEVER had them survive more than 2 weeks after a dusting plus it's pretty cheep, and you don't need much. it's without a doubt more effective than sand.

also sand wont change your ph, it's basically inert, small chunks of glass...there is a windshield company near my place, they make it with mostly sand from the riverbed that the factory is located on, and a few extra ingredients
 
S

SeaMaiden

Not all sand is silica-based, senor. That's why I said to take a small container of vinegar and pour it on the sample in question. This is what fish and reefkeepers do when sourcing sand for tanks, but we want the calcareous sand.

Did you know that you cannot use silica-based sands to keep sharks, especially young sharks? It will abrade their skin to the point of infection and death, damn near every time.
cyat said:
none of that will work from my experience.
done the sand, d.e. powder, and 2 sizes of d.e stones, perlite, cedar,cinnamon, crabshell, topdressings. and bt didnt work for me either.
wanna find a natural remedy, still looking tho.
alternating with gonats, neem, and sm 90 now and its not really working

other stuff to try dryer sheets, potato slices, and pyretherin drench?

good luck
Click to expand...
Then you're not dealing with fungus gnats, but instead are likely dealing with root aphids. The Flying Mothers. All those other methods work very well for reducing or eliminating fungus gnats.

Pyrethrin drench should help with RAs, though you may have to go with a strong product like Evergreen, Pyganic or similar.

Also, the typical drying out session that's used to control fungus gnats actually encourages root aphids to spread.
 
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