I am having a hard time getting rid of insects in my potting soil. My plants are droopy. I have applied a good amount of diatomaceous earth to all of them, even to the roots, but these insects don't seem to want to leave. They are white and very tiny. What can I do?
Without a picture of the soil and the insects it is very hard to tell but the most likely identification is:
If your plants are outside and getting too much water that would match the wilted look the leaves have. The roots are stressed or dead and cannot provide water to the leaves.
Diatomaceous earth might work but it will only catch insects on the surface, not eggs or adults underneath the soil. Read the links for other methods including the last resort method of 5 ml of bleach to one litre of water poured through the plant. Pour more water through after a few minutes. This will kill the fungus gnats but it may kill the plant. Try drying the plant out for a no risk solution.
Please read the links to answers from this site and let us know if the description and solution does the job.
You still haven't said what soil you've used in the pots for these plants, but the insects you're seeing, if they're really white and don't fly, could be root aphids or simply soil mites. If the plants are obviously suffering, go and buy some sterilized potting soil (any proprietary ones will be sterilised) take the plants out of their pots, sit them in buckets of water, wash off all soil and anything else you can see that shouldn't be there without damaging the roots. Thoroughly clean and sterilize your pots, then replant using the new, sterilized soil.
