Grow Tip: Fungus Gnats - by Ben Horner

Fungus Gnats are pesky little flying insects that can devastate a crop of medical marijuana if gone untreated. These tiny flies have two small clear wings and thin long legs. These bugs have a 25-35 day life cycle, most of which is in larva form. Adults lay eggs in the grow media, and/or roots. After the eggs hatch, the larvae feast on the fungus in the soil and on the roots
of the plants.

To determine how bad your infestation is, place a few slices of potato on the top of your medium
for 5 hours then remove and observe under a microscope. If the is many larva (see picture) you are going to have to treat your soil. To do so, don’t water for a couple days and allow the topsoil to dry. Then mix Hydrogen peroxide (H2O2) with water, 1:4 ratio. Hang yellow fly strips to kill the adults. The same ratio should be used for hydro systems.

Often, store purchased peat soils have fungus gnats eggs dormant in the bag, adding coco to your
mix can help. Uncovered drains and pooled water can also be breeding grounds for these pests. Keeping your grow clean is very important. Neem oil solutions are an excellent organic preventative, and will keep away most bugs if used regularly. Neem oil should be sprayed on stalks and fan leaves every three weeks.

Over the counter pesticides are not recommended for obvious reasons, but may be the only hope for seriously infested situations.

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