Georgofili World

Newsletter of the Georgofili Academy

Drosophila suzukii a new pest for wine grape

Grapes are amongst the dozens of host plant fruits that are attacked by Drosophila suzukii (Matsumura). The first report of attacks of D. suzukii on grape dates back to 1925 in Japan. Recordings of D. suzukii on grapes were made subsequent to its recent invasion into  Europe and North America.
D. suzukii, can oviposit into fully intact grape berries of certain cultivars.  These oviposition wounds may also provide pathways of infestation for other drosophilids and spoilage bacteria. The oviposition levels intensifies as berries mature.  This is due to physiological changes during grape berry development.  Such changes include increase in sugar content and a decrease of penetration force. Concerning this last parameter, penetration levels below 40 cN results in an exponential increase in oviposition. 
Some grape varieties display this penetration level before harvest.  These varieties becoming particularly susceptible to attack by D. suzukii. These varieties should deserve the utmost attention when monitored to assess the presence of D. suzukii attack and the possible risk of sour rot development and other drosophilids.

Claudio Ioriatti -