Sciarid pests (Diptera: Sciaridae) from undercover crop production in South Africa

Keywords: Afrotropical diptera, Bradysia impatiens, invasive species, Lycoriella ingenua, Lycoriella sativae

Abstract

Fungus gnats (sciarids) are among the most important pests in undercover crop production. They cause direct physical damage to plant roots, transfer fungal pathogens and create entry points for soil-borne plant pathogens. In 2007, Bradysia impatiens, an important fungus gnat pest was found in association with major tree nursery beds in the Mpumalanga and KwaZulu-Natal Provinces of South Africa and was considered invasive. In this study, eight greenhouses were surveyed in the Western Cape Province and B. impatiens was found to be present in all the greenhouses. Similar to the results of the previous studies, a high haplotype diversity was identified for B. impatiens, which may indicate multiple strain introductions into South Africa. Two  other fungus gnat species, Lycoriella sativae and Lycoriella ingenua – globally important sciarid pests of mushroom cultures – were identified as new from South Africa. Through a laboratory culture, the life cycle of B. impatiens was observed to be approximately 21 days at 25 °C. Females laid between 100 and 250 eggs. Possible introduction sources include contaminated vegetative material and growth media, thus there maybe need to revise the importation restrictions on these commodities. The identification of two novel species of sciarid pests that have only previously been identified in the Holarctic region could further emphasise this need. However, the recent discovery of such high sciarid diversity could also be due to only a few studies having been previously done on sciarid pests in South Africa.

Significance:

  • The fungus gnat species Bradysia impatiens is reported as present in several undercover crops in the Western Cape Province of South Africa, including cucumbers, tomatoes, chrysanthemums, mushrooms, blueberries and various herbs.
  • Lycoriella ingenua and Lycoriella sativae were also found to be present in mushroom gardens – the first report of Lycoriella from the Afro-tropical region.
  • The three fungus gnat species are some of the most important sciarid pests in undercover crop production worldwide. This study highlights the need for more studies on the distribution of these sciarids and possible invasion history.

Open data set:

https://www.ncbi.nlm.nih.gov/popset?DbFrom=nuccore&Cmd=Link&LinkName=nuccore_popset&IdsFromResult=1654675097

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Published
2020-03-26