Sesame (Sesamum indicum L.) Response to Diuron Applied at the 3- and 4- Leaf Pair Stage of Development

Aims: Studies were conducted to evaluate sesame response to diuron at 1X (1.12 kg ha-1), 2X (2.24 kg ha-1), and 4X (4.48 kg ha-1) the labeled US rate applied at 3- or 4 leaf pair growth stage.

Study Design: Treatments consisted of a factorial arrangement of three diuron rates (1.12, 2.24, and 4.48 kg ha-1) and two application timings (3-leaf pair or 4-leaf pair). An untreated check was included in each study with 3-4 replications depending on location.

Place and Duration of Study: In south-central Texas near Yoakum (29.2765o N; -97.1237o W) and the High Plains of Texas near New Deal (33.7354o N; -101.7369o W) during the 2022 growing season.

Methodology: Sesame variety ‘S-4302’ was seeded 1.0 to 2.0 cm deep under conventionally tilled conditions. Weeds were controlled either by hand-hoeing or with the use of postemegence herbicides. Plot size was two rows (76 cm apart) by 8.9 m at Yoakum and four rows (101 cm apart) by 9.5 m at New Deal. At New Deal, only the two middle rows were sprayed and the other rows were untreated and served as buffers. Sesame was harvested with a small plot combine. An analysis of variance was performed using the ANOVA procedure for SAS to evaluate the significance of herbicides and application timing on sesame response and yield. Fisher’s Protected LSD (0.05) was used for separation of mean differences.

Results: Sesame stunting was evident at both locations and increased as diuron rate increased. Stand reductions were noted at Yoakum as diuron at 4.48 kg ha-1 resulted in a 9% stand reduction compared with <1% with diuron at 1.12 or 2.24 kg ha-1. Also, application timing had an effect on sesame growth.

Conclusion: Sesame yields decreased as the diuron rate increased at the High Plains location but not the south-central Texas location while application timing had no effect at either location.