HOST-PLANT RELATIONS OF THE HALL SCALE (HOMOPTERA, DIASPIDIDAE) ON PEACHES AND NECTARINES IN ISRAEL

The population density of the Hall scale, Nilotaspis halli (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 cl osely 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 b uds. A good correlation between the number of scales in twig band trap s and densities on buds suggests that the traps may be useful for moni toring. Winter buds infested by high densities of scales failed to spr out by spring. Scale feeding on nectarines causes red spots that becom e gradually darker over time; damage to peaches appears later, closer to picking time. The delayed appearance of discoloration in peaches su ggests that late or light scale infestations may not result in economi c damage. Egg development was suspended over winter, but resumed simul taneously on different early- and late-ripening varieties. The resumpt ion of reproduction occurred at threshold temperatures that varied wit h the duration of exposure to low temperatures.