The objective of this study was to evaluate the costs of biologically controlling infestations of silverleaf whitefly, Bemisia argentifolii Bellows & Perring, in New England greenhouse operations on poinsettia, Euphorbia pulcherrima Wild. ex Koltz, using the parasitic wasp Encarsia formosa Gahan (Nile Delta strain). Partial budget analysis was used to compare costs for conventional verses biological control regimens. Four alternative whitefly control budgets are developed; two conventional chemical-based control budgets formulated with and without the use of imidacloprid, and two biological control budgets which demonstrate the impact of possibly greater pest monitoring efforts necessary to implement this type strategy successfully. The analysis shows that biological whitefly control costs were >300% greater than conventional chemical-based control strategy costs. Most of this increase is caused by the higher costs of Encarsia formosa as the material control input. If monitoring costs are held constant across different strategies, labor costs actually decline for biological control. This is because of a significant reduction in the number of control applications made and the relatively lower cost of applying E. formosa. If more extensive monitoring efforts are required to implement biological control successfully, labor costs increase by 56% over the conventional pre-imidacloprid regimen. Based on these results, the authors conclude that cheaper and more reliable means of producing E. formosa must be developed before this strategy will become economically viable for commercial poinsettia greenhouse production.