Oviposition and emergence of olive scale (Homoptera: Diaspididae) crawlers: Regional degree-day forecasting model

Abstract

We investigated the temperature-driven onset and rate of oviposition and egg hatch of the spring generation of the olive scale, Parlatoria oleae (Colvée), in northern Israel. Phenology was studied between 1992 and 1994 at different elevations (between 80 and 820 m above sea level) and on 2 different host species (apple, Malus silvestris Miller, and pear, Pyrus communis L.). The association between accumulation of degree-days (DD) and rate of oviposition and egg hatch was analyzed with simple linear regression using 10°C as the lower developmental threshold temperature and 15 February as the starting date Temperature-driven rates of oviposition and egg hatch were similar for the 3 yr, all elevations, and the 2 tree species. Elevation, host species, and year did not meaningfully affect the amount of thermal units required by P. oleae to initiate oviposition and egg hatch. Oviposition and egg hatch is expected to begin at 40.1 and 184.8 DD, respectively. The model accurately predicted the onset of egg hatch during 2 yr consecutively in 1 tested plot (deviations between observed and expected dates of <3 d).