The invasive plataspid Megacopta cribraria (F.) is now distributed throughout much of the southeastern United States. While it readily feeds and develops on the invasive weed kudzu, Puereria montana (Loureiro) Merrill var. lobata (Willdenow), M. cribraria is an economic pest of soybean, Glycine max (L.) Merrill. Differences in the susceptibility of soybean to M. cribraria-induced yield reductions based on plant phenology were assessed using two experimental protocols in Georgia, North Carolina, and South Carolina from 2011 to 2013 in which soybeans were protected from M. cribraria using insecticides during different stages of plant phenology. In the first protocol, where insecticide applications were initiated at progressively later stages in soybean development depending on treatment, yields in the untreated plots were reduced by an average of 13% compared with plots that were protected beginning at full flowering (R2). Soybean plots that were protected beginning at 4 wk after full flowering or earlier did not suffer yield reductions from M. cribraria. In the second protocol, where insecticide applications began at R2 and were discontinued at progressively later stages in soybean development depending on treatment, yields in the untreated plots were reduced by an average of 12% compared with plots that were protected until 8 wk after R2. Plots in which protection was discontinued beginning at 4 wk after full flowering or later did not suffer yield reductions. The period from two to 6 wk after R2 (generally coinciding with pod and seed development – stages R3-R5) was identified as critical for management of M. cribraria.