Host-Plant Relations of the Hall Scale (Homoptera: Diaspididae) on Peaches and Nectarines in Israel

Abstract

The population density of the Hall scale, Nilotaspis hall (Green), on peaches and nectarines in Israel showed 3 peaks during the year. Male nymphs were rare and present only in summer. Winged adult males were not present. Population density was significantly higher under buds closely attached (adpressed) to twigs compared with those that were more protruding. Cultivars with a higher proportion of adpressed buds had greater densities of scales than those with predominantly protruding buds. A good correlation between the number of scales in twig band traps and densities on buds suggests that the traps may be useful for monitoring. Winter buds infested by high densities of scales failed to sprout by spring. Scale feeding on nectarines causes red spots that become gradually darker over time; damage to peaches appears later, closer to picking time. The delayed appearance of discoloration in peaches suggests that late or light scale infestations may not result in economic damage. Egg development was suspended over winter, but resumed simultaneously on different early- and late-ripening varieties. The resumption of reproduction occurred at threshold temperatures that varied with the duration of exposure to low temperatures.