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Environmental Impact

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News Article

Forest ecosystems may be under threat from invasive fruit fly

Drosophila suzukii is a well-known pest of fruit crops

The spotted wing drosophila (SWD), introduced from South-East Asia is a recognised agricultural pest of fruit crops.  However, recent research has found that this insect may also pose a threat to forest ecosystems, by attacking the fruits of various forest trees and plants, which can have far-reaching ecological consequences, as well as competing with other frugivorous (fruit-eating) species.  The study has been published in the journal NeoBiota.

The research team, comprising of scientists from the Swiss Federal Institute for Forest, Snow and Landscape Research WSL and the Ökobüro Biotopia investigated the use of host plants at 64 sites in different forest communities across Switzerland from mid-June to mid-October 2020.  The team examined more than 12,000 fruits for SWD egg deposits and they also recorded symptoms of fruit decay after deposition to determine whether SWD attacks on fruit triggered the decay. In addition, the researchers monitored the presence of SWD with cup traps baited with apple cider vinegar, assuming that the SWD would outnumber and potentially outcompete other fruit-eating insects.

Egg deposits were identified on the fruits of 31 of the 39 fruit bearing forest plant species, with 18 species exhibiting an attack rate of more than 50%.  Additionally, more than 50% of the plant species showed severe symptoms of decay after egg deposition.  The study authors suggest that attacks by SWD may change the attractiveness of fruits, because they alter their chemical composition and visual cues such as shape, colour and reflective patterns which could mean that seed dispersers such as birds, consume less fruit.

Due to the large number of infested fruit, significant ecological impact was to be expected.  According to Prof. Martin M. Gossner, entomologist at WSL, "rapid decay of fruits attacked by the spotted wing drosophila results in a loss of fruit available for other species competing for this resource, and may disrupt seed-dispersal mutualisms due to reduced consumption of fruit by dispersers such as birds. If the fly reproduces in large numbers, both seed dispersers and plants could suffer."

The team also noted that there was a high abundance and dominance of SWD in the trap catches.  This showed that the more SWD present, the less abundant the native drosophilids were, which suggests additional negative impacts of SWD on the native species.

The authors conclude that with ongoing climate change, these potentially severe ecological consequences could be amplified within temperate forests, since higher average and winter temperatures may lead to shorter generation times and lower winter mortality, eventually increasing pressure on forest fruits and the competitiveness of SWD over native drosophilids.


Journal reference

Irene Bühlmann, Martin M. Gossner. Invasive Drosophila suzukii outnumbers native controphics and causes substantial damage to fruits of forest plantsNeoBiota, 2022; 77: 39 DOI: 10.3897/neobiota.77.87319


Further information

Detailed information on Drosophila suzukii including distribution, biology, host/species affected etc. is available on CABI’s Invasive Species Compendium

Subscribers to the Environmental Impact database can find further information on Drosophila suzukii.  For example using the search string "Drosophila suzukii" AND ("plant pest" OR “insect pest” OR "invasive species") yields over 460 results.  A selection of these records is provided in the further reading section below.

Article details

  • Date
  • 09 November 2022
  • Source
  • Neobiota
  • Subject(s)
  • Biodiversity
  • Climate Change