**6. Conclusion/recommendations**

these experiments: pyroxasulfone (40 to 160 g ha−1), pendimethalin microencapsulated (ME) (1064 g ha−1), and saflufenacil (60 g ha−1). There was no stand reduction in any of the experiments for any PRE herbicide treatment where the average wheat stand was 21 (**Table 2**), 21 (**Table 3**), 22 (**Table 4**), and 24 (**Table 5**) plants per meter of row (data not shown). Even when pyroxasulfone was applied 12 days PRE (12 DPRE), no reduction in stands occurred (**Table 3**) (data not shown). These data indicate the crop safety which these herbicides, pyroxasulfone, pendimethalin ME, and saflufenacil PRE, have toward soft red winter wheat in this region.

Soft red winter wheat injury ranged from 0 to 20% across PRE treatment timings for all studies when evaluated at 14, 15, or 30 DAP (**Tables 2**–**5**). Pyroxasulfone PRE at 160 or 120 g/ha injured wheat 20 and 11% (**Tables 2** and **3**), respectively. This injury was in the form of stunting. Some stunting from pyroxasulfone was still visible at 90 DAP for the 80 and 160 g ha−1 rates (**Table 2**). However, this injury was transient by the end of the season and not observed. Metribuzin applied alone or in combination with pendimethalin ME at emergence resulted in significant injury, 18%, at 30 DAP (**Table 4**). The soils for the present studies were a sandy loam, loamy sand, or sandy clay loam with less than 2.0% organic matter. Hulting et al. [52] noted 3% or less wheat injury from pyroxasulfone rates up to 100 g ha−1 on a silt loam soil. Previous research indicated decreased pyroxasulfone injury with legumes grown in soils with greater clay contents [19]. Canadian dry bean research indicated that pyroxasulfone injury at 210 g/ha was 11% or less [55]. These data indicate that at rates up to 160 g ha−1 wheat had tolerance in sandy loam, loamy sand, and sandy clay loam soils of the Southeastern United States. When pyroxasulfone was POST applied at Feekes scale 1.0–1.9 (**Tables 2**, **4**, and **5**), no injury was ever observed. Pyroxasulfone has limited POST activity but can be applied after wheat emergence per label recommendation [47–49]. This will provide growers an opportunity to incorporate a residual herbicide to promote weed control. When pinoxaden, diclofop, or mesosulfuron was POST

The AE and POST for these herbicide applications did not affect wheat stand.

204 Wheat Improvement, Management and Utilization

applied, wheat injury did occur but was consistently less than 9% (**Tables 2**–**4**).

Wheat yield varied by location and by year (**Tables 2**–**5**). There were no differences for yield when pyroxasulfone was PRE applied (**Table 2**) or 12DPRE and PRE (**Table 3**) as compared to AE or POST applications of diclofop, pyroxsulam, mesosulfuron, or pinoxaden. For these experiments, yield exceeded 4000 kg ha−1 for all pyroxasulfone treatments and was always greater than the nontreated control. There was no rate response for wheat yield for pyroxasulfone rates of 40, 60, 80, 100, or 120 g ha−1 (**Tables 2** and **3**). There were no differences in wheat yield as compared to the nontreated control when pyroxasulfone was applied alone or in combination with saflufenacil PRE, AE, or POST (**Table 4**). Wheat yields in this set of experiments (four totals) were consistent with early season injury, in that metribuzin alone or in combination with pendimethalin ME-applied AE had significant injury 30 DAP, and this translated into reduced yields of 5670 and 5350 kg ha−1, respectively. Previous research indicated that metribuzin reduced yield demonstrating the risks growers take when using this herbicide for weed control [16, 31, 33]. Early-season Italian ryegrass control for pyroxasulfone application at 40 to 160 g ha−1 12DPRE or PRE was 72 to 99% when evaluated at 30 DAP (**Tables 2**–**4**). However, by 175 DAP Italian ryegrass control began to decline to 83% and less for the 40 and 60 g ha−1 rates of pyroxasulfone. Pyroxasulfone at 80 g ha−1 or greater provided 87% or greater season-long control (**Tables 2**–**4**). Previous research has noted similar Italian ryegrass response to pyroxasulfone at 50–150 g/ha

This research indicated that using the appropriate rates of pyroxasulfone PRE could provide season-long control of Italian ryegrass in wheat. However, variability in Italian ryegrass control was observed when low rates or improper timing of application were used, which indicates the need for further development as growers incorporate this herbicide. Eight different soft red winter wheat cultivars were used in this research, and all exhibited tolerance to pyroxasulfone alone and with other herbicide combinations. Future research should be conducted with the currently evaluated herbicides for control of other weed species. Italian ryegrass control was attained and maintained with the appropriate herbicide applications, but variability can be an issue if proper rates and timings are not adhered to. This should be considered as an area for future research efforts in soft red winter wheat production using combinations of these herbicides. Growers should follow registration recommendations for the herbicides evaluated in this research, along with crop rotation and using different mechanisms of action herbicides to limit exposure and reduce potential for resistance to proliferate.
