Relative activity comparison of aminocyclopyrachlor to pyridine carboxylic acid herbicides

AbstractThe pyridine carboxylic acid (PCA) herbicide family can exhibit differential activity within and among plant species, despite molecular resemblances. Aminocyclopyrachlor (AMCP), a pyrimidine carboxylic acid, is a recently discovered compound with similar use patterns to those of the PCA family; however, relative activity among PCAs and AMCP is not well understood. Therefore, the objective of this study was to quantify relative activity among aminopyralid, picloram, clopyralid, triclopyr, and AMCP in canola, squash, and okra using dose-response whole-plant bioassays. Clopyralid was less active than all other herbicides in all species and did not fit dose-response models. Aminopyralid and picloram performed similarly in squash (ED50 = 21.1 and 23.3 g ae ha−1, respectively). Aminopyralid was 3.8 times and 1.7 times more active than picloram in canola (ED50 = 60.3 and 227.7 g ha−1, respectively) and okra (ED50 = 10.3 and 17.3 g ha−1, respectively). Triclopyr (ED50 = 37.3 g ha−1) was more active than AMCP (ED50 = 112.9 g ha−1) and picloram in canola. Aminocyclopyrachlor (ED50 = 6.6 g ha−1) and triclopyr (ED50 = 7.8 g ha−1) were more active in squash than aminopyralid and picloram. In okra, AMCP (ED50 = 14.6 g ha−1) and aminopyralid (ED50 = 10.3 g ha−1) performed similarly but were more active than triclopyr (ED50 = 88.2 g ha−1). Herbicidal activity among AMCP and PCAs was vastly different despite molecular similarities that could be due to variable target-site sensitivity among species.

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Influence of Diflufenzopyr Addition to Picolinic Acid Herbicides for Russian Knapweed (Acroptilon repens) Control

Weed Technology ◽

10.1614/wt-08-184.1 ◽

2009 ◽

Vol 23 (3) ◽

pp. 450-454 ◽

Cited By ~ 2

Author(s):

Stephen F. Enloe ◽

Andrew R. Kniss

Keyword(s):

Carboxylic Acid ◽

Carboxylic Acids ◽

Picolinic Acid ◽

Weed Species ◽

Pyridine Carboxylic Acid ◽

Russian Knapweed ◽

Pyridine Carboxylic ◽

Acroptilon Repens ◽

Acid Herbicides

Diflufenzopyr is a synergist that has improved the efficacy of certain auxin-type herbicides such as dicamba on many broadleaf weed species. However, little is known regarding the activity of diflufenzopyr with other auxin-type herbicides. Russian knapweed is an invasive creeping perennial that is susceptible to certain pyridine carboxylic acids, which are auxin-type herbicides. The objective of this research was to determine if the addition of diflufenzopyr to three pyridine carboxylic acid herbicides enhances long-term control of Russian knapweed in Wyoming. All treatments were applied in the fall. Treatments included aminopyralid (0, 0.05, 0.09, and 0.12 kg ae/ha), clopyralid (0, 0.16, 0.21, 0.31, and 0.42 kg ae/ha) and picloram (0, 0.14, 0.28, 0.42, and 0.56 kg ae/ha), applied with and without diflufenzopyr (0.06 and 0.11 kg ae/ha). Twelve mo after treatment (MAT), diflufenzopyr had no significant impact on Russian knapweed control with either aminopyralid or picloram, and had significant but inconsistent impacts on knapweed control with clopyralid. At 24 MAT, diflufenzopyr did not enhance Russian knapweed control with either aminopyralid or clopyralid and was slightly antagonistic with picloram. These results indicate that the addition of diflufenzopyr does not improve Russian knapweed control with fall applications of either aminopyralid, clopyralid, or picloram.

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Residual Herbicide Effect on Interseeded Annual Clover in Southern Forage Systems

Weed Technology ◽

10.1017/wet.2018.20 ◽

2018 ◽

Vol 32 (4) ◽

pp. 454-460

Author(s):

Jennifer J. Tucker ◽

M. Kimberly Mullenix ◽

Stephen F. Enloe ◽

Pat L. Burch

Keyword(s):

United States ◽

Carboxylic Acid ◽

Early Summer ◽

Pyridine Carboxylic Acid ◽

Crimson Clover ◽

Herbicide Treatment ◽

Weed Cover ◽

Pyridine Carboxylic ◽

Residual Herbicide ◽

Acid Herbicides

AbstractAcross the southeastern United States, pyridine carboxylic acid herbicides are widely used for broadleaf weed control in permanent grass pastures. This family of herbicides has proved very successful for controlling most broadleaf weeds commonly present in southeastern pastures and hayfields. In the southern United States, producers have expressed concern when overseeding legume species into warm-season perennial sods following application of commonly used pyridine carboxylic acid herbicides, as legumes are generally highly sensitive to this herbicide family. Field experiments were established to evaluate two herbicide treatment programs (residual vs nonresidual) on crimson clover overseeded into bermudagrass sod. The residual herbicide program included aminopyralid plus 2,4-D (0.09 + 0.7 kg ae ha–1), and the nonresidual program included triclopyr plus fluroxypyr (0.63 + 0.21 kg ae ha–1) plus 2,4-D (1.12 kg ae ha–1). Herbicide programs were applied at two key timings: in spring (May) and early summer (June). Spring applications were also evaluated when used in single vs repeated annual application. Our results did not indicate soil residual herbicide issues for crimson clover planted in the fall following spring or early-summer application of aminopyralid + 2,4-D at either location. Additionally, there were no cumulative negative impacts on crimson clover following 2 yr of spring herbicide application. Crimson clover cover, however, strongly decreased as grass and weed cover increased––an event that may be related to greater interspecific competition at higher levels of grass and weed cover. Soil fertility, weather, and competition from resident annual grasses and weeds strongly influenced productivity, suggesting that changes in pasture dynamics had a greater influence on clover productivity than did herbicide treatment or timing of application.

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