thanks for all the replies.
my guess is that avocado lace bug is the problem. the link provided by guadua (thank you!) had photos that looked exactly like my plants.
from the linked article:
''Wolfe et al. (1949) stated that it preferred the West Indian “race” of avocado, although no variety was known to be free from attack.'' which may explain why the damage was most severe on the pollack and less on the adjacent lula and oro negro.
although an article from the california avocado commission:
(
https://www.californiaavocadogrowers.com/cultural-management-library/controlling-damage-caused-avocado-lace-bug) had a different take:
''AVOCADO TREE VARIETIES VARY IN SUSCEPTIBILITY TO AVOCADO LACE BUG. West Indian x Guatemalan avocado hybrids appear to be particularly resistant to attack.
Hass avocados (a Mexican-Guatemalan hybrid) can be severely damaged by lace bug outbreaks.''
i've just spent an hour or more wandering around the internet looking for solutions. it appears that there is no real danger to the tree (even with extensive leaf drop) but that it can be a recurring problem season after season.
most suggestions for control start with some form of predator or insecticidal soaps or oils (which seems to have mixed success), or systemic insecticides (imidacloprid) which they say may provide the most effective control, although with some risk to beneficial species.
i guess, for now, i'll just keep spraying the neem oil weekly and see what happens.
really appreciate all the help. : >)
best,
mike