Assessment of the damage potential of three thrips species on white variety table grapes— In vitro experiments

Abstract

The reddish ring spot on white variety table grapes c.v. Soultanina is a novel symptom caused by thrips-feeding activity at the touch points. It is an important cosmetic damage observed on ripe grape berries. In this study the damage potential of the three most abundant thrips species ( Frankliniella occidentalis, Thrips tabaci and Drepanothrips reuteri) in the vineyards of Crete was investigated in the laboratory. It was demonstrated that these thrips species are potential casual agents of reddish ring spot symptom. F. occidentalis was significantly more injurious, causing more than 90% damage in 8 days, and 100% in 16 days, combined with severe fungal infection. T. tabaci and D. reuteri caused 76.7% and 45.3% damage on grape berries respectively in 16 days. In addition a novel reddish linear symptom on grape berries was associated with D. reuteri infestation. The development of thrips on grape berries was also investigated. The first F. occidentalis larvae was observed 6 days after artificial infestation and the development period (larvae to adult) on ripe grapes was 10 days (25 °C). T. tabaci development on grapes was partially impaired. The first larva was observed 16 days after infestation and the development period was 12 days (25 °C) combined with high larvae mortality. D. reuteri larvae development on grape berries was not observed. However, it is not clear whether this resulted from prohibited oviposition or delayed/impaired egg development.