Pre-emergent Annual Ryegrass Control

Demonstration of the efficacy and crop safety of various pre-emergent herbicides and application timings of Boxer Gold and prosulfocarb.

Hines Hill, WA, 2018

Summary

Annual ryegrass (ARG) is a major issue inwinter cropping systems. Lack of integrated weed management (IWM), as well astight rotations and over reliance on chemical options, has seen an increase inseed banks across WA, especially in the lower rainfall zones.

Atrial site was established in Hines Hill, at a location with a known heavy ARGburden. The aim was to demonstrate and evaluate the efficacy and safety ofvarious pre-emergent products/combinations, including EPE/PSPE applicationtimings of prosulfocarb and new and pipeline chemistry for the control ofLolium rigidum (Annual Ryegrass). The trial included a ploughed block for thesecond replica, this allowed for the treatments to be assessed under bothno-till and till conditions.

Overall Sakura in combination with trifluralinor Boxer Gold EPE provided the best control of ARG in wheat (90-95%). Long residualactivity of Sakura is a key factor in reducing seed set of ARG, similarly BoxerGold and prosulfocarb EPE, delivered an extended period of residual activityand protection. Trifluralin on its own provided the least amountof control overall (20-40%), indicative of ARG group D resistance? Phytotoxicitywas observed for F9600 as well as EPE timed applications of Boxer Gold and prosulfocarbat 42 DAT (5-10%).

Methodology

Treatment List

Trial Design

Site, Crop and Application Details

Assessment Methods

Data Analysis

All data analysis in this report was conducted using Microsoft Excel. Simple means, analysis of variance was used to determine statistical significance using the least significant difference method with a 95% confidence interval.

Results

Block 1 (No-Till)

Figure 1: Block 1, average % control of ARG in Scepter wheat across four DAT ratings.

Trifluralin provided theleast amount of control overall (40%), potential indication of Group Dresistance. In contrast, Trifluralin + Sakura was second to Sakura + Boxer EPEin delivering the greatest control over ARG, with final ratings of 90% and 95%respectively. Trifluralin in combinations with Prosulfocarb EPE extendedresidual activity, therefore was able to target later germinating ARG (70-80%control). Triflur X and Avadex Xtra + Trifluralin had initial control (70-80%),however; declined (50 -60%) in efficacy over time, failing to reduce seed set.

BAS684 has provided 75% control vs Sakura and Boxer Gold which achieved 85% and 65% control respectively. Performance of BAS684 standalone was excellent. On the 42DAT ratings BAS684 and Sakura looked very similar. However, Sakura proved to hold on the longest and provide better protection to later germinating ryegrass.

Block 2 (Tilled)

Figure 2:Average % control of AGR in scepter wheat across four assessed DAT.

The two-way plough stimulated a higher weed germination, as well as burying the ARG seed below the chemical band. This resulted in a higher pressure placed on the chemicals as well as decreased efficacy. The Sakura + Trifluralin mix performed well considering, maintaining persistent residual protection resulting in a final control of 95%. The EPE applications of Boxer Gold and prosulfocarb held off the ryegrass with a final control rating of ~70%. All other treatments including Sakura standalone, BAS684 & Boxer Gold showed a good level of control at 42DAT but dropped off in efficacy rapidly after that.

Figure 3:Average phytotoxicity % ratings for reps 1&2 taken 28 & 42 DAT. Taken as percentage of plant effected by a chemical treatment.

Figure 4: Vigor reductions seen 28 DAT in Trifluralin mixes by 5-10% of the untreated control.

Mild symptoms of phytotoxicity were presentat 28 DAT (Fig. 3), high winds early in the season saw a large incidence oftreated soil being blown into rows, where emerging wheat was adversely affectedby chemical residue. Ratings taken 42 DAT indicated the effects were transientwith the exception of EPE applications of prosulfocarb. Visual assessmentsreported vigor reduction for Trifluralin + Prosulfocarb as well as EPEtreatments (5-10%) (figure 4).

Conclusion

Overall Sakura in combination withTrifluralin or Boxer EPE provided the best control of ARG in wheat (90-95%). Whenexposed to higher weed burden in block 2, Sakura + Trifluralin came out on top(95%), demonstrating its extended residual activity, where other herbicides declinedin residual activity under high pressure. Applying prosulfocarb EPE offered anextended period of protection, therefore was able to target later germinatingARG, subsequently reducing seed set.

BAS684 standalone proved to be similar/slightly behind Sakura and similar/slightly better than Boxer Gold. There were no phytotoxicity issues and product handling was good. In 2019 we would like to investigate/demonstrate BAS684 with suitable tank-mix partners. BAS684 provides a new mode of action for ARG control in the wheatbelt, vital for helping extend the life of our existing chemistry.