Population dynamics and seasonal trend of California red scale (Aonidiella aurantii Maskell) in citrus in Northern Spain

Abstract

The California red scale, Aonidiella aurantii (Maskell), was detected in citrus in Catalonia, Northern Spain, in 2000, and has since spread slowly and irregularly southwards, with foci of infestation currently found in southern Tarragona citrus-growing areas. Since Catalonia is the northern citrus growing area in Spain, between 2002 and 2009, the A. aurantii biological cycle (male flights and seasonal history) was studied in two citrus groves and compared with other regions and countries. Population dynamics showed that 4 male flights occur (including that of the overwintering generation) in May, mid June-mid July, August and in October, the most abundant being in August (over 60% of males captured throughout the year). The thermal constant estimated between male flights, using 11.7 ºC as the lower threshold temperature, was 611.8 ± 35.5 DD. Three peaks of sensitive instar were also observed, in early June, late July-early August, and late September. The number of crawlers captured reached a maximum on 27 May (± 1.85 days), 24.8 ± 2.5 days (184.2 ± 18.1 DD) after the first male flight. The male flight abundance showed there was a relationship only between two consecutive generations, revealing the rapid shifts in population abundance. We estimated when the first sensitive instar peak occurred through a non-destructive method, based on the peak of males captured during the first flight.