The grapevine aphid, Aphis illinoisensis: thermal requirements for development and its performance on six grapevine cultivars
The grapevine aphid, Aphis illinoisensis (Shimer), has invaded various regions in the Mediterranean basin. The aim of this study was to determine the thermal requirements for aphid development and to assess its performance on six grapevine cultivars of economic importance in Greece. The grapevine aphid was reared at four constant temperatures (17 - 26 degrees C) on 'Soultanina' and 'Agiorgitiko' cultivars and the thermal summation method was applied to estimate the lower developmental thresholds and the thermal constants in each cultivar. In addition, age-specific life tables were constructed and population growth parameters on cultivars 'Soultanina', 'Savvatiano', 'Moscato Bianco', 'Agiorgitiko', 'Mavrodafni' and 'Merlot' were estimated at 23 degrees C. Our data revealed that aphids develop faster with increasing temperatures within the 17 - 26 degrees C range on both cultivars. The theoretical lower developmental threshold was 4.2 degrees C and 5.4 degrees C and 110.9 and 104.1 day-degrees were required for aphids to reach adulthood on 'Soultanina' and 'Agiorgitiko', respectively. Mean adult longevity and mean post-reproductive period varied significantly among cultivars. Aphids lived significantly longer on 'Savvatiano' than on 'Moscato Bianco', 'Soultanina' and 'Mavrodafni', and the longest post-reproductive period were recorded for aphids reared on 'Savvatiano', 'Agiorgitiko' and 'Merlot'. However, mortality and developmental rates, mean lifetime fecundity and population growth parameters didn't differ significantly among grapevine cultivars. Overall, our data showed that all examined cultivars are suitable hosts for the aphid. This study is the first dealing with the development and population growth of A. illinoisensis related to temperature and the results contribute to better understanding the biology of the species and improve pest management practices.