Damage and nuisance

Unlike other fruit flies which are attracted to mature or decaying fruit, D. suzukii is able to cause direct damage without the presence of injury and on healthy berries. In fact, this species attacks the intact grape berry, before ripening, thanks to its laying organ (ovipositor) allowing it to perforate the skin of healthy berries to lay its eggs (figure 1).

The larvae consume the pulp which causes the appearance of a partial collapse of the berry before it completely disintegrates (figure 2).

Drosophila suzukii is generally observed more particularly on black grape varieties. Indeed, this fly is attracted especially by dark-colored fruits, hence more marked attacks on small fruits in general: strawberries, raspberries, blackberries, cherries, etc. where this insect has been causing serious damage in recent years.

The creation of egg-laying wounds leads to the development of secondary parasites such as yeasts and bacteria responsible for acid rot and usually transmitted by Drosophila melanogaster on overripe fruits (therefore rather on white grape) or some saprophytic fungi such as Rhizopus stolonifer also involved in the liquefaction of the fruit or Botrytis cinerea responsible for gray rot.

Bibliography:

Delbac L et al. (2015) Vector diseases. Acid rot and fruit flies. Union Girondine des Vins de Bordeaux, special issue, April, 50-52

Laveau et al. (2016) Drosophila suzukii in the vineyard: what's new in 2015? Union Girondine des Vins de Bordeaux, 1130, 53-59