Phenology of the Apple Blossom Weevil Anthonomus pomorum (L.) (Coleoptera, Curculionidae) on Apple Trees in Moscow against the Backdrop of Global Warming

Abstract

The results of observations for four consecutive years (2016–2019) on the preimaginal development of the apple blossom weevil (Anthonomus pomorum (L.), Coleoptera: Curculionidae) on apple trees of the old Russian cultivar ‘Antonovka’ in Moscow are presented. Observations were carried out and samples of infested buds taken over the whole developmental period every 3–6 days. The phenology of the weevil from the start of activity of overwintered beetles to the appearance of the first new-generation adults and to their mass emergence from the shelter buds is described. Due to the significant climate warming during the 22 years preceding 2019, the duration of the developmental stages of this insect has noticeably decreased. In particular, in our studies, the duration of preimaginal development of the apple blossom weevil (from the first egg laid to the first new-generation adults and from the mass oviposition to the mass emergence of the adults inside damaged buds) in Moscow averaged 26 days and that including the period spent by the adult in the bud was 27 days. The mean air temperatures during this developmental period ranged from 14.5 to 14.8°C. This duration of preimaginal development of the pest is less than that recorded in Moscow in 1979–1982 and in Vladikavkaz (North Ossetia) in the mid-1920s. There were high correlation coefficients between the duration of the weevil egg-to-adult development, on the one hand, and two characteristics of heat resources, on the other: the mean temperature over the developmental period and the sum of effective temperatures above 6°C. These respective coefficients were –0.977 and –0.852 for the period until the emergence of the first adults from shelter buds and –0.971 and −0.899 for the period until mass adult emergence. These correlation coefficients suggest that both metrics characterizing heat resources can be used to estimate the duration of the apple blossom weevil development, although the mean temperature seems to be more reliable for the periods of supplementary feeding and oviposition. Taking into account the changed duration of the developmental stages of the apple blossom weevil would improve the phenological forecasts for this pest and the efficiency of its control, including application of insecticides and release of natural enemies.