1. 
   polyetic
   Of plant disease epidemics: Continuing from one growing season to the next.
   Found op http://ppathw3.cals.cornell.edu/glossary/Defs_P.htm
   
   
2. 
   Polyetic
   Pertaining to a sequence of least two years, as in polyetic epidemic, one in which disease progresses for more than one year.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   

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