Potential use of herbicides for powdery mildew control in transgenic soybean

Genetic engineering has facilitated the development of more productive crops with enhanced capabilities for pest and weed management. The transgenic soybean variety DAS44406-6, known as Enlist E3™ (E3), combines genes for insect resistance (Bt) and tolerance to herbicides such as glyphosate, 2,4-D, and glufosinate-ammonium. While this technology has proven effective for weed and insect control, its impact on disease behavior, particularly powdery mildew, remains unclear. This study aims to assess the potential of herbicide applications to reduce severity of powdery mildew in E3 soybeans. We tested preventive and curative treatments against powdery mildew in post-emergence E3 soybeans. Three assays were carried out with six treatments (NC - not controlled; 2,4-D; Glu — glufosinate-ammonium; Gly — glyphosate; Gly + 2,4-D; and PC – positive control with fungicide) and four repetitions in a completely randomized design. The area under the disease progress curve (AUDPC) was assessed. The disease inhibition occurred in both preventive and curative treatments, showcasing a systemic and residual effect. On average, glyphosate + 2,4-D, glyphosate, and glufosinate-ammonium reduced powdery mildew severity by 88.28%, 74.06%, and 64.41%, respectively. The isolated application of 2,4-D did not alter the disease severity during applications at the V4 stage. This pioneering study demonstrates that the E3 technology may confer advantages for powdery mildew management in addition to its well-established benefits for weed and insect control.