Impact of planting dates on yield and resistance of soybean varieties to soybean stem fly (Melanagromyza sojae) in Egypt

Late planting dates can significantly reduce soybean yield due to fluctuations in soybean stem fly infestation levels in soybean crops. A two-year study was carried out at ARC, Giza, Egypt during 2020 and 2021 summer seasons to assess varietal performance to the infestation of soybean stem flies during three planting dates. Comparing to planting soybeans in mid-June, planting soybeans in mid-May resulted in increased days to maturity by 6.29% in the first season and 8.04% in the second season, increased seed yield per plot by 12.88% in the first season and 10.94% in the second season, and improved yield attributes such as 100-seed weight and pods per plant. Planting Giza 111 and Giza 35 in mid-May produced 2.78 and 2.75 kg/plot in the first season, and 2.40 and 2.43 kg/plot in the second season, respectively, with minimal stem fly infestation (52.77 and 47.49% damage reduction in the first season, and 40.00 and 39.94% damage reduction in the second season, respectively). Planting Dr-101 in mid-June produced 2.45 and 2.31 kg/plot in the first and second seasons, respectively, with minimal stem fly infestation (20.93 and 12.34% damage reduction in the first and second seasons, respectively). Planting Giza 111 and Giza 35 in mid-May is the best approach to maximize seed yield while reducing damage from soybean stem flies. Alternatively, planting Dr-101 in mid-June could also be a suitable option for achieving high yields with minimal pest infestation.