The word depopulates is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 20
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (50 words)
apostle, applets, apposed, auletes, dapples, delates, delouse, deposal, deputes, elapsed, elodeas, eluated, eluates, epaulet, laptops, loudest, oleates, outlead, outleap, outsped, papules, pasteup, peapods, peopled, peoples, pestled, petaled, pleased, pleated, pulsate, pupated, pupates, saluted, sauteed, sepaled, slapped, slopped, speedup, spouted, stapled, stepped, stopped, tadpole, toppled, topples, toupees, tousled, updates, uploads, upslope