Abstract
AbstractRapid crop canopy formation is important to reduce weed emergence and selection for herbicide resistance. Field experiments were conducted in 2017 and 2018 in Fayetteville, AR, to evaluate the impacts of PRE applications of flumioxazin on soybean injury, soybean density, canopy formation, and incidence of soil-borne pathogens. Flumioxazin was applied at 0, 70, and 105 g ai ha−1 to predetermined flumioxazin-tolerant and -sensitive soybean varieties. Flumioxazin at 70 g ha−1 injured the tolerant and sensitive varieties from 0% to 4% and 14% to 15%, respectively. When averaged over flumioxazin rates, density of the sensitive variety was only reduced in 2017 when activation of flumioxazin was delayed 7 d. Compared to the tolerant soybean variety, flumioxazin at 70 g ha−1 delayed the sensitive variety from reaching 20%, 40%, 60%, and 80% groundcover by 15, 16, 11, and 5 d, respectively. No delay in canopy closure (95% groundcover) was observed with either variety. Consequently, no yield loss occurred for either variety following a flumioxazin application. Flumioxazin did not impact root colonization of Didymella, Fusarium, Macrophomina, or Rhizoctonia. Pythium colonization of the soybean stem was increased by flumioxazin in 2017, but not in 2018. Increased injury, delays in percent groundcover, and an increase in Pythium colonization of soybean following a flumioxazin application may warrant the need for other soil-applied herbicides at soybean planting. Alternatively, soybean injury and delays in percent groundcover following flumioxazin applications can be mitigated through appropriate variety selection; however, comprehensive screening is needed to determine which varieties are most tolerant to flumioxazin.
Highlights
Flumioxazin is a protoporphyrinogen oxidase-(PPO) inhibiting herbicide Group 14 that is used in soybean production for preplant or PRE control of small-seeded broadleaves and annual grass weeds (Taylor-Lovell et al 2001, 2002; Yoshida et al 1991)
The objective of this research was to determine whether flumioxazin resulted in delays in soybean canopy development and affected the incidence of soil-borne pathogens
Flumioxazin applied at 105 g ha−1 to the sensitive and tolerant varieties caused 21% to 30% and 4% to 8% visible injury, respectively, at 21 d after planting (DAP)
Summary
Flumioxazin is a protoporphyrinogen oxidase-(PPO) inhibiting herbicide Group 14 that is used in soybean production for preplant or PRE control of small-seeded broadleaves and annual grass weeds (Taylor-Lovell et al 2001, 2002; Yoshida et al 1991). PPO-inhibiting herbicides were used extensively to control Amaranthus ssp. Before the release of glyphosate-resistant crops (Norsworthy et al 2012). Following the evolution of glyphosate-resistant Amaranthus ssp. The use of PPO-inhibiting herbicides increased (Norsworthy et al 2012). PPO-resistant Palmer amaranth [Amaranthus palmeri (S.) Wats.] was first confirmed in Arkansas in 2015 (Salas et al 2016). PPO resistance has been confirmed in seven states (Heap 2019; Varanasi et al 2018). The evolution and spread of PPO-resistant Palmer amaranth has called into question the utility and importance of these herbicides for weed control in soybean
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