Development of Lycoriella ingenua and Bradysia impatiens on different phases of agaricus composts

Abstract

Fungus gnats are small, dark colored, mosquito like fragile insects. They can be encountered all around the world, excluding places with extreme climate. Gnats prefer habitats that are damp with high relative humidity and rich in organic debris. Most of the species are not considered to be harmful in agriculture, but some may cause serious damage, especially in forcing of vegetable or ornamental plants. In mushroom production, however, they are considered as the most destructive pests; the damage caused by them alone can result in huge loss for mushroom farmers. In the Hungarian mushroom industry, fungus gnats damage mainly white-button mushroom, oyster mushroom and pioppino productions. Lycoriella ingenua (Dufour, 1839) and Bradysia impatiens (Johannsen, 1912) are the two most commonly found fungus gnat species from the family Sciaridae on Hungarian mushroom farms. We have conducted an experiment with the two aforementioned species, to find out, whether they can fully develop into adults, feeding purely on Agaricus compost diet. We used unspawned white button mushroom compost (phase 2) and spawned compost which has been colonized by the mycelia of Agaricus bisporus (phase 3). We did not conduct any experiment with the first compost phase, as it undergoes pasteurization, which eliminates any pests in it. We recorded emerging gnats only from phase 2 compost. Neither L. ingenua, nor B. impatiens could complete its development on phase 3 compost diet, furthermore not even pupae were observed in these breeding pots. From pots containing phase 2 compost, a total of 1607 adults emerged. The number of B. impatiens adults was 653, and 954 for L. ingenua. Sex ratios for the two species were different. For B. impatiens, the number of females was 1.36 times greater than that of males, in L. ingenua there were 1.7 times more males than females in total. Swarming took approximately 6 days for B. impatiens and 10 days for L. ingenua. From the experiment we can conclude that phase 3 compost, which is well interwoven with Agaricus bisporus mycelia is not suitable for B. impatiens and L. ingenua to complete their whole life cycle.