Plant attacker for February 2020: The fruit fly Bactrocera dorsalis

fruit fly

Egg laying female Bactrocera dorsalis fruit fly - USDA photo by Scott Bauer

Bactrocera dorsalis is a small fly species (length: 8 mm) from the family of fruiting or boring flies (Tephritidae). It originates from outside Europe and its presence within Europe is to be avoided at all costs. This fruit fly can affect many fruit species and therefore cause major economic damage in the European fruit and vegetable growing and horticulture sector. The measures imposed to prevent the introduction of Bactrocera dorsalis in Europe are therefore stringent.

The females lay eggs with their ovipositor just below the fruit skin (see image). These eggs produce larvae that feed on the flesh, causing enormous crop losses. Damaged fruits can be recognized by a brown spot around the drill hole in which the egg was laid. Eventually, the entire fruit rots.

Bactrocera dorsalis, and by extension also other non-European fruit flies, are regularly detected in Belgium during import checks on plant products, so-called 'phytosanitary checks', at our border inspection posts. The introduction of these exotic fruit flies is mainly via their larvae, which grow up to 10 mm in size (see image) and are hidden in imported fruit of mango, sweet pepper, soursop (Graviola) and orange, among others. Bacterocera dorsalis is currently not present in our regions, but was first detected in large numbers in Europe in 2018, more specifically in a field in Italy. It is suspected that the introduction of this fly species took place through the import of infected fruits. It is therefore very important not to bring fruits from non-European countries into Europe!

To prevent the introduction of this invasive insect, phytosanitary checks are carried out by the Federal Food Agency (FASFC) and suspect samples are then further checked by the ILVO for the presence of B. dorsalis or other non-European fruit flies. If such fruit flies are detected, the cargo must be destroyed. This prevents the possible introduction and spread of non-European fruit flies in our regions. Recently, a research project was started at the ILVO to speed up the identification of the larvae of these fruit flies (FPS project 'TEPHRIFAST').

Bactrocera larva and rotten (brown) flesh

Bactrocera larva and rotten (brown) flesh - photo ILVO