Growth of Soybean Stressed by Nematodes, Herbicides, and Simulated Insect Defoliation

Abstract

Soybean [Glycine max (L.) Merr.] responses to combinations of stress factors generally are unknown. Research was conducted in 1989, 1990, and 1991 to quantify growth responses to stresses from soybean cyst nematode (SCN; Heterodera glycines Ichinohe), acifluorfen {5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoic acid} plus bentazon [3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide] herbicides, and simulated green cloverworm [GCW; Plathypena scabra (F.)] defoliation. Treatments were combinations of at‐planting SCN soil density, acifluorfen plus bentazon rate, and simulated GCW defoliation level. Herbicides were applied at V6 soybean development, and GCW feeding was simulated from R2 to R4 soybean development. Plant growth was quantified at V4, R2, and R4 developmental stages. Herbicide stress was assessed by leaf stomatal conductance and visible foliar injury. Herbicides reduced conductance and caused visible injury each year, and limited growth (plant height, leaf area, pod number, and dry weight of leaf, pod, and stem plus petiole) in 1990 and 1991. Likewise, defoliation reduced leaf area each year, but reduced growth (plant height and leaf dry weight) in 1990 and 1991 only. Uncontrolled environmental factors probably confounded growth responses in 1989. Although no herbicide × defoliation effects on growth were found, defoliation caused greater reductions in canopy quantity and quality for herbicide‐injured plants in 1990 and 1991. Targeted stress from SCN was achieved in 1990, and interaction with herbicides decreased conductance, increased visible herbicide injury, and reduced leaf area, plant height, pod number, and pod dry weight. These data support the potential for stresses from SCN and acifluorfen plus bentazon to cause more‐than‐additive reductions in soybean growth.

Soybean Growth and Development as Affected by Glyphosate and Postemergence Herbicide Tank Mixtures

“…Various studies have reported differential sensitivity between soybean cultivars to herbicides; however, sensitivity was not linked to additional herbicide resistance in the cultivar (Connelly et al, 1988; Dayan et al, 1997; Griffin and Habetz, 1989). Other research has evaluated the application of acifluorfen and bentazon [3‐(1‐methylethyl)‐(1 H )‐2,1,3‐benzothiadiazin‐4(3 H )‐one 2,2‐dioxide] at the V3 (Levene et al, 1998) and V6 (Browde et al, 1994) stage of development and the interaction with nematodes. However, published research evaluating soybean canopy influence as affected by herbicide treatment for weed control and white mold suppression is not available.…”

Absence of Interactive Responses of Early Soybean (Glycine max) Growth to Soybean Cyst Nematode (Heterodera glycines), Postemergence Herbicides, and Soil pH and Texture1

“…In a previous study, the application of acifluorfen plus bentazon reduced leaf area and stomatal conductance, thus decreasing soybean yield (Browde et al 1994a). Importantly, the effect of the herbicide injury was more dramatic when other stresses were present.…”

“…Furthermore, no interactions between herbicides and SCN D were observed for injury (Table 6). It has been observed that acifluorfen plus bentazon applications reduced soybean growth, and this was more evident in the presence of high SCN egg soil densities (Browde et al 1994a). Nevertheless, it cannot be ruled out that the combined effect of acifluorfen and bentazon on soybean growth was more important than the effect of acifluorfen alone, which could explain why we did not observe interactive responses between acifluorfen and SCN D .…”

WebGro: A Web‐Based Soybean Management Decision Support System

“…However, other factors such as diseases, insects, and hail damage can also cause significant yield loss. Although herbicide injury has been shown to not significantly affect yield, it can contribute to yield loss if other stresses are present (Browde et al, 1994). Producers can use management to alter the effect of interactive stresses.…”