Variation in the susceptibility of blackberry varieties to Drosophila suzukii infestation

Abstract

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is an invasive polyphagous species, that is frequently found in blackberry culture, affecting the commercial value of fruits. Between 2020-2021, in the blackberry collection of the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca (Romania), were carried out observations on susceptibility of five cultivated varieties (‘Thornless’, ‘Loch Ness’, ‘Thornfree’, ‘Thornless Evergreen’ and ‘Navaho’) to D. suzukii. In 2020, the attack frequency in the whole collection was 78.2%. ‘Thornfree’ had the highest attack frequency, 89% while ‘Loch Ness’ was the least susceptible with a frequency of attack of 71%. In 2021, the overall proportion of damaged fruits in the collection was 59.6%. The most susceptible was ‘Thornless’ with an attack frequency of 66% and ‘Thornless Evergreen’ with only 49%. The incidence of infestation by the spotted-wing Drosophila suzukii is influenced by the thermal characteristics of the year, with temperatures higher than 30 °C impacting the fertility of females and the viability of eggs. In the year 2020, the average number of larvae per fruit collected was 6.4, while the average number of larvae in the ‘Loch Ness’ cultivar was 9.4, with a maximum of 48 larvae per fruit. In 2021, an average of 3.4 larvae per fruit were observed, with variations ranging from 2.8 larvae in the ‘Thornfree’ cultivar to 4.2 larvae in the ‘Navaho’ cultivar.