The Collaborative International Dictionary of English v.0.48:

Plague \Plague\, v. t. [imp. & p. p. Plagued; p. pr. & vb. n.
   Plaguing.]
   1. To infest or afflict with disease, calamity, or natural
      evil of any kind.
      [1913 Webster]

            Thus were they plagued
            And worn with famine.                 --Milton.
      [1913 Webster]

   2. Fig.: To vex; to tease; to harass.
      [1913 Webster]

            She will plague the man that loves her most.
                                                  --Spenser.
      [1913 Webster]

   Syn: To vex; torment; distress; afflict; harass; annoy;
        tease; tantalize; trouble; molest; embarrass; perplex.
        [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "plaguing":
   aggravating, annoying, blandishment, bothering, bothersome,
   buttonholing, cajolement, cajolery, cajoling, chafing, coaxing,
   demanding, disquieting, distressful, distressing, disturbing,
   dunning, exasperating, fretting, galling, harassing, importunate,
   importunateness, importune, importunity, insistent, irking,
   irksome, irritating, nagging, pesky, pestering, pestiferous,
   pestilent, pestilential, plaguesome, plaguey, plying, pressing,
   pressure, provoking, teasing, tiresome, tormenting, troublesome,
   troubling, upsetting, urgency, urgent, urging, vexatious, vexing,
   wearisome, wheedling, worrisome, worrying