White insects swarming on my potting mix

[habitat_gardener]

For houseplants, I mulch with perlite to avoid fungus gnats....probably not cost effective for greenhouse plants, though.

[Grayson]

Thanks for all the help. Am currently working on a way to keep the excess rainfall out of the soil. The black garbage bag keeps getting blown away by the wind (will try to use sturdier packing tape). Also, how long should I keep that "cover" because I would also want the soil to be "solarized" regularly.

If those are what adult fungus gnats look like then these guys might be springtails (I hope). It was a hot day yesterday so they should've been reduced somewhat. As for the other one, if they are a form of flea beetle, what is the best form of control? Manual crushing or do I need a spray?

[gorbelly]

Originally Posted by Grayson

Also, how long should I keep that "cover" because I would also want the soil to be "solarized" regularly.

Solarization is a specific procedure in which clear plastic is used to trap the sun's energy and superheat soil for a long time to a temperature that kills organisms. Is that what you're trying to do? Because I'm not sure you could achieve that on your balcony, and it would most likely kill your tomato plant's roots. It's also not something you do "regularly", as it takes weeks to months, depending on the strength of the sun in your area.

If you mean you want the sunlight to directly hit the top of your soil, I'm not sure why. What do you think is the benefit?

Originally Posted by Grayson

If those are what adult fungus gnats look like then these guys might be springtails (I hope).

Adult fungus gnats fly. They are often mistaken for fruit flies, but when you look closely, they look more like mosquitoes.

Their larvae are white, translucent maggots that are about half a cm long. They are soft and slimy, generally move very slowly, and leave slime trails if they come to the surface.

(images from http://ipm.ucanr.edu/PMG/PESTNOTES/pn7448.html)

There are springtails. As you can see, you can't really mistake them for fungus gnat larvae once you know what to look for--they look totally different.

(image from http://www.extension.umn.edu/garden/...d/springtails/)

Originally Posted by Grayson

As for the other one, if they are a form of flea beetle, what is the best form of control? Manual crushing or do I need a spray?

If it's a flea beetle, the damage will be very minor. You might see some tiny round holes that look like pinpricks in the lower leaves of the plant. It will not be enough damage to affect tomato production at all. Not worth worrying about and not worth spraying for.