Fungus gnats (Sciarids)

Controlling fungus gnats using nematodes

Fungus gnat larvae (Lycoriella spp., Bradysia spp.) can cause considerable damage in ornamental flower and mushroom cultivation. The milky white larvae are around 5 mm long and live in the soil. They eat the roots of seedlings, cuttings and young plants, hollow them out and in so doing create points of entry for putrefying bacteria and soil-borne fungus.

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Figure 1: Fungus gnat larvae

Adult fungus gnats are 2-4mm long and are active during the day. They are easy to identify owing to their two long antennae and their slow, erratic way of flying. A gnat lives for 3 to 7 days and lays up to 40 eggs during this time in moist soil, turf or decomposing vegetable matter. Development from the egg to a gnat takes around 3 weeks under optimal conditions (24°C).

For many years now, nemaplus® has proven to be an ideal control agent. It contains Steinernema feltiae nematodes.

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Figure 2: Lifecycle Sciarid Flies

Application

The soil temperature should be 8-28 °C. The effect of the nematodes lessens with higher temperatures. Treat as early as possible following sowing or planting of the cuttings. One application usually provides protection for six weeks. The soil should be damp but not wet. Nematodes are unable to move in waterlogged soil. As nematodes are sensitive to direct sunlight, apply nemaplus® when cloudy or during the evening or early morning hours.

Application quantities

Figure 2: Fungus gnat larvae infested with nematodes

Figure 3: Fungus gnat larvae infested with nematodes

0.5 million nematodes per m² or 5,000 nematodes per litre of turf. In the case of a serious infestation, vulnerable plants or a high proportion of compost in the soil, increase the application quantity to 1 million per m² or 10,000 nematodes per litre of soil. An overdose does not have any negative impact. Water: 10-50 litres per 100m². If possible, avoid watering prior to application so the soil does not become too wet.