An integrated weed management strategy for the control of horseweed (Conyza canadensis)

Abstract

Multiple herbicide-resistant populations of horseweed [Conyza canadensis (L.) Cronquist] continue to spread rapidly throughout Ontario, notably in areas where no-till soybean [Glycine max (L.) Merr.] is grown. The occurrence of multiple herbicide resistance within these populations suggests that the future role of herbicide tank mixtures as a means of control will be limited. An integrated weed management strategy utilizing complementary selection pressures is needed to reduce the selection intensity of relying solely on herbicides for control. Field studies were conducted in 2018 and 2019 to test the hypothesis: if fall-seeded cereal rye (Secale cereale L.) can reduce C. canadensis seedling density and suppress seedling growth, then the interaction(s) of complementary selection pressures of tillage, cereal rye, and herbicides would improve the level of C. canadensis control. Laboratory studies were conducted to determine whether the allelopathic compound 2-benzoxazolinone (BOA) affected the root development of C. canadensis seedlings. The interactions observed among multiple selection pressures of tillage, cereal rye, and herbicides were inconsistent between the 2 yr of study. A monoculture of cereal rye seeded in the fall, however, did reduce seedling height and biomass of C. canadensis consistently, but not density. This reduction in seedling height and biomass was likely caused by the allelopathic compound BOA, which reduced seedling root development. Control of C. canadensis seedlings in the spring required the higher registered rates of dicamba or saflufenacil. The addition of shallow fall tillage and the presence of cereal rye did not improve the variability in control observed notably with 2,4-D or the lower rates of saflufenacil or dicamba. With the implementation of complementary weed management strategies, environmental variables in any given year will likely have a direct influence on whether these interactions are additive or synergistic.

Vertical tillage effects on crop production and pest management in Pennsylvania

“…Other studies measuring impact of vertical tillage on crop yield report varying results. In one study, vertical tillage increased soybean yield (Watters & Douridas, 2013), while another study reported increases in corn yield after vertical tillage but not soybean yield (Van Dee, 2005). Several cooperating farms within this study have invested in planter technologies, such as automatic and pneumatic adjustment of row-unit down pressure and closing wheel systems of various types.…”

“…Trends from a small body of research suggest that vertical tillage may improve crop performance, including crop stand establishment and crop yield (Van Dee, 2005;Watters & Douridas, 2013). Many growers use vertical tillage tools to create a warming and drying effect on soil conditions to achieve timelier planting and more even crop emergence and establishment in high-residue environments.…”

“…(2012) reported that control of small, early‐emerging annual weeds with a preplant rotary harrow equipped with non‐concave and non‐angled coulters was comparable to burndown herbicides. Use of shallow tillage implements (<10‐cm working depth) has produced variable levels of Erigeron canadensis L. control (Brown &Whitwell, 1988; Chahal & Jhala, 2019; Vanhie et al., 2021), which is a facultative winter annual with variable emergence patterns (Buhler & Owen, 1997).…”

Sustainable Crop and Weed Management in the Era of the EU Green Deal: A Survival Guide

“…Tillage, though, has a major role in a reduction in seed germination and may be associated with reduced herbicide rates to achieve a high control of weeds. For instance, the application of 350 g ae ha −1 of 2,4-D ester in horseweed (Conyza canadensis) provided equal control in terms of weed biomass and density reduction compared to higher doses of 2,4-D (600 or 850 g ae ha −1 ) in spring sprayings after shallow fall tillage [92]. However, it should be noted that reduced sublethal herbicide rates might cause crop phytotoxicity and yield reductions, as indicated by research regarding the effects of sublethal rates of synthetic auxin herbicides in soybean production [93].…”