Technical Abstract: New phosphonate reagents were developed for the two-carbon homologation of aldehydes to methyl- or ethyl-branched unsaturated aldehydes and used in the practical synthesis of (2E,4E,6E,8E)-7-ethyl-3,5-dimethyl-2,4,6,8-undecatetraene (1), a pheromone of the beetle, Carpophilus lugubris. The phosphonate reagents, diethyl ethylformyl-2-phosphonate dimethylhydrazone and diethyl 1-propylformyl-2-phosphonate dimethylhydrazone contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde followed by removal of the dimethylhydrazone protective group with a biphasic mixture of dilute HCL and petroleum ether. This robust two-step process replaces the standard three-step aldehyde homologation route using ester-based Horner-Wadsworth-Emmons reagents. The new synthesis of 1 from (2E)-2-methyl-2-butenal was run on a 10-gram scale and required just five steps (two cycles of condensation and deprotection followed by a final Wittig olefination) instead of the usual seven. In addition, the Wittig olefination step was simplified, and its E-isomer selectivity was improved. The overall yield for the entire synthetic pathway was increased from 20 percent to 37 percent, enhancing the commercial potential of Carpophilus pheromones.