... Continued ...
FUNGUS GNATS is an oft cited problem when growing indoors. When infestation is serious, the larvae will proceed to eat tender root hairs of seedlings and stunt or kill them. Even more mature plants can be affected due to lack of vigor making them susceptible to other infections and infestations, I had a SERIOUS problem with them delaying and stunting growth of my pepper seedlings last year. I've done the blowing them away while outside -- I used a hand air pump for inflating party balloons. Indoors, I use the vacuum cleaner hose to suck up as many flying and crawling gnats as I can, each time, recalling Edna Mose's strict injunction: "Noooo CAPE! No CAPE!" (
Incredibles)as the gnats, clinging literally for their live's worth, are vacuumed up by the betraying wings caught up in the airstream.
I decided to trust that Bt
var. israelensis is not harmful to human beings
https://npic.orst.edu/factsheets/BTgen.pdf
...and that the Mosquito Bits which contain Bti impregnated in ground corn cob bedding do not contain any additional toxic or chemical ingredients in the inactive "Other Ingredients" It has been approved for organic use, FWIW.
I mix a small amount into potting mix, a spoonful in a jug of water, and/or scratch some into the surface. I also sprinkle some in the catch trays so that excess water from the bottom is inoculated and re-absorbed into the bottom of the container soil.
For dealing with the adults, best and least stressful method for me is to set out containers of soapy water to dive into. Flowery or fruity scented suds work the best -- I use a scented children's bubble bath that I bought accidentally. I can't take the smell in a bathtub -- too strong, but a small container can be tolerated. They are best placed near the soil surface level or around the base of the pots. Bright white containers and surfaces attract them very well.
When I come across them, I catch and put centipedes in my containers. They will eat earthworm eggs and babies, which can be a negative, but I believe superior control of fungus gnat larvae by the centipedes supersedes this concern.
I used to try controlling fungus gnat adults and larvae on the soil surface by sprinkling ag/hort quality (I.e. NOT heat processed NOT pool filter) diatomaceous powder. But even thorough dusting did not phase the adult gnats -- they simply crawled out covered in white dust and flew off. The powders become useless when dampened.
However, in trying to find a good alternative to perlite -- dry dust from perlite makes me retch and have constricted dry throat, leading to asthma. I feel it's likely to be nearly as dangerous as asbestos when inhaled. And finding pumice gravel to be too heavy in potting mixes and overall expensive. I settled on UltraSorb, which is diatomaceous earth pulverized to perlite size sharp gravel. I get the "plain" kind with no other additives. This is a product often recommended by Bonsai folk for inorganic growing medium. I incorporate something like 1/3 C to 2 cups of potting mix. Sometimes more.
I believe when dry, the DE gravel form dangerously moisture robbing surfaces that help to dry up the gnat larvae and eggs. As they wear down to powder with use, they become like the DE powder. The ag quality DE powders are added to grain and feed and sometimes fed to farm animals as internal vermicide, so I assume they are less harmful -- in any case, they do not cause the respiratory reaction I get from perlite dust.
Combined use of all of these this year has been helping to control the fungus gnats.
...more to follow...