Flight activity of alate Adelgids (Homoptera, Aphidoidea) in southern England

Abstract

The flight periods of eight species of Adelgids were deduced from suction trap catches in a mixed woodland site at Alice Holt, Hampshire from 1965 to 1970. Nine species from other natural forest areas in the northern hemisphere occurred on trees in the study area, but some immigration may have contributed to the numbers trapped. Large catches (often >200 individuals per day) of three pest species, Adelges laricis Vall., A. cooleyi (Gill.) and Pineus pini (L.), occurred during late May and June. Only small catches (<10 individuals per day) were obtained during July–September. The sexuparae from the non-Picea hosts occurred mainly in May and June whereas the gallicolae from Picea hosts flew during certain periods from June to September. Analysis showed that the threshold temperature for flight was 16°C and that 64% or more of the total monthly catch occurred in the afternoon (13·00–19·00 h). The variation in length of the early summer flight period by ± one week was related to air temperature maxima, but the fluctuation ( ± one week) in the mean date for flight of each species in the early summer period is probably connected with the phenological condition of the host-plant.