polyetic

Of plant disease epidemics: Continuing from one growing season to the next.
Found on http://ppathw3.cals.cornell.edu/glossary/Defs_P.htm

Polyetic

Pertaining to a sequence of least two years, as in polyetic epidemic, one in which disease progresses for more than one year.
Found on http://www.encyclo.co.uk/visitor-contributions.php
No exact match found