I have an ongoing pest issue in my garden and maybe you do, too. Maybe you’ve seen the little black fliers moving to and from along you soil line. These are most likely fungus gnats. Never heard of them? Well, if you have moist, black, nutrient-rich soil, you probably have fungus gnats. I have them in all of my raised beds and even in my beloved composter at times. Of course, they aren’t too much of a nuisance right now during the coldness of winter, but I can already imagine what is going on below the soil line where it is nice and warm and moist.
It
is not the flying adult fungus gnats that are the problem; rather it is the
soil-bound larval stage. They eat fungus in the soil (hence, the name) and
since that same soil fungus, called mycorrhiza, is attached to the tiny plant
root hairs, it damages the plant, too. In seedlings it is deadly. In more
mature plants, you get stunting, poor production and death in hot temperatures.
In root plants, you get really ugly produce.
The
best and easiest treatment is through the use of beneficial
bacteria. Prepare a soil drench with one of the commercial preparations
available and use as directed. This will usually work, but I am afraid I need
to go stronger.
Soil
solarization is a way to nuke every living thing in your soil without using harmful
chemicals. It is very simple to do as long as there are no plants growing in
the area you plan to solarize. All you have to do is wait for sunny days to
come, stretch some clear plastic over the area like a mini-greenhouse, then
allow the soil to be baked inside by the sun. High temperatures will kill all
the living things in the top 6-inches or so of the soil. The longer you leave
it, the better it is. An added benefit is you can kill a lot of weed seeds,
too. You can find much more detailed instructions here.
There
are some drawbacks, though. You are actually killing everything that is alive
including the beneficial fungus the gnats are eating. So once you are done, you
will need to add compost to your soil to build up the soil profile so it is
healthy. Also, in colder climates you may lose that area for the season because
your temperatures aren’t warm enough. However, even if you solarize for a short
time and kill most of the bad guys it will benefit you. Follow that up with the
beneficial bacteria soil drench and the garden should produce treasures untold.
How
do I keep the little buggers out? Well, the best way is to buy seeds instead of
seedlings. There are no gardens anywhere near mine and I suspect that my
original infection came from my store-bought tomato seedlings or at least the
soil surrounding them in the pot. If you do use store-bought seedlings, you can
look closely at the soil first for obvious signs of gnats. Also, you can wash
the roots carefully but thoroughly before you plant them. An additional step
would be to continue to drench your soil at least once a season and even add
some beneficial
fliers to your garden.
Good luck and good hunting!
