Fungus fly
Fungus flies, also known as sciarid flies, are common pests in indoor cannabis grows, especially in humid conditions. High humidity favors the development of these insects. They are uncommon outdoors due to weather conditions.
High humidity and temperature are the determining factors in egg-to-adult development. At 25°C, approximately twenty days are needed to complete development, while at 20°C, about forty days are required.
The development of these phytophagous organisms is related to the high humidity of the substrates.
A major infestation can develop in just a few weeks, as an adult female fungus gnat can lay hundreds of eggs under favorable conditions during her life cycle.
Fungus fly damage
The most damaging stage for cannabis plants is during the larval phase. This larval phase can last up to almost thirty days under certain conditions. During this time, the larvae feed on root hairs and roots, preventing the plant from performing its physiological functions. As a result, symptoms such as chlorosis, necrosis of the leaflet tips, and wilting appear. These symptoms are often associated with infestation by this insect, but its diagnosis can sometimes be confused with other nutritional deficiencies.
Another effect of these flies can be seen in the root system, which often takes on a more yellowish or brownish color.
The larvae remain in the substrate near the roots and near the neck, but in very serious cases they can feed on other parts of the plant such as the internal tissues of the stem.
In addition to the direct damage caused by fungus gnats, they are also important vectors of other pathogens, such as fungi. Many root and vascular fungi take advantage of the wounds caused by the larvae, and these fungi ultimately kill cannabis plants. The winged flies can also carry fungal spores from one container to another, thus spreading the disease.
CONTROL METHOD
For the prevention of fungus gnats:
- Place yellow and blue insect-trapping cards in the facilities.
- Reduce ambient humidity.
- Remove leaves from the lower parts of the plants to facilitate ventilation at the base of the plant and at the same time promote the drying of the first few centimeters of the substrate.
Root treatments with neem oil have proven relatively effective in limiting fungus gnat larvae populations in potted crops.
But the most effective control is achieved through biological control by carrying out repeated applications with the entomopathogenic nematodes Steinernema felti