We investigated the potential of disrupting pheromone-mediated mating communication in European corn borer, Ostrinia nubilalis(Hubner). The female sex pheromone, a blend of (Z)-11-tetradecenyl acetate and (E)-11-tetraecenyl acetate and (E)-11-tetradecenyl acetate in a ratio of~97:3 was released from two dispenser types and in two deployment patterns, a Shin-Etsu rope of formulation spaced 2m apart and a widely-spaced(35m) pattern using a controlled release system called the Metered Semiochemical Timed Release System (${MSTRS}^{TM}$). Both dispensers were situated in grassy sites that constitute aggregation areas for O. nubilalis mating activity within and around cornfields at three different locations in Iowa. Pheromone-emission rate (after 7 days in the field) from the ${MSTRS}^{TM}$(6.09$mu extrm{g}$/min) was ca. 26 times greater than from the rope formulation (0.23 $mu extrm{g}$/min). Both dispensers during both first and second flights achieved a significant level of disruption of pheromone-source location(averaging 97%). More importantly, a significant level of mating disruption was achieved, as measured by the frequency of mating by free-flying feral females. The mean number of matings, as measured by spermatophores, per first generation female was 1.33 in the $MSTRS^{TM}$ plots and 1.58 in the rope plots, compared with 1.88 in untreated check plots. During the second flight, the number of matings per female averaged 1.63 in the $MSTRS^{TM}$ plots, 1.56 in the rope plots and 2.17 in untreated check plots. There was also a significant reduction in the proportion of females that mated at least once during both flights in $MSTRS^{TM}$ plots. During the first flight, 17 and 10% fewer females mated in the $MSTRS^{TM}$-treated and rope-treated fields, respectively. A similar level of disruption was also achieved during the second flight.