Investigation into interactions of environmental and application time effects on 2,4-D and dicamba-induced phytotoxicity and hydrogen peroxide formation

Abstract

Application timing and environmental factors reportedly influence the efficacy of auxinic herbicides. In resistance-prone weed species such as Palmer amaranth (Amaranthus palmeri S. Watson), efficacy of auxinic herbicides recently adopted for use in resistant crops is of utmost importance to reduce selection pressure for herbicide-resistance traits. Growth chamber experiments were conducted comparing the interaction of different environmental effects with application time to determine the influence of these factors on visible phytotoxicity and hydrogen peroxide (H2O2) formation in A. palmeri. Temperature displayed a high degree of influence on 2,4-D and dicamba efficacy in general, with applications at the low-temperature treatment (31/20 C day/night) resulting in an increase in phytotoxicity compared with high-temperature treatments (41/30 C day/night). Application time across temperature treatments significantly affected 2,4-D–induced phytotoxicity, resulting in a ≥30% increase across rates with treatments at 4:00 PM compared with 8:00 AM. Temperature differential had a significant influence on dicamba efficacy based on visible phytotoxicity data, with a ≥46% increase with a high (37/20 C day/night) compared with a low differential (41/30 C day/night). Concentration of H2O2 in herbicide-treated plants was 34% higher under a high temperature differential compared with the low differential. Humidity treatments and application time interactions displayed undetected or inconsistent effects on visible phytotoxicity and H2O2 production. Overall, temperature-related influences seem to have the largest environmental effect on auxinic herbicides within conditions evaluated in this study. Leaf concentration of H2O2 appears to be generally correlated with phytotoxicity, providing a potentially useful tool in determining efficacy of auxinic herbicides in field settings.

Characterization and inheritance of dicamba resistance in a multiple-resistant waterhemp (Amaranthus tuberculatus) population from Illinois

“…Resistance indexes of 5.6 and 10.6 were obtained for the R parental line relative to WUS in the two runs, respectively. The resistance index differences are potentially an artifact of environmental factors leading to an increase in sensitivity in the WUS population (Table 3), which previously have been shown to have an effect on the resistance level for synthetic auxin herbicides (Johnston et al 2019).…”

“…a multigenic trait. It is important to note that parental F 1 lines also had relatively broad distributions, which can be attributed to lack of homogeneity within parental line, environmental variation in dicamba response (Flasiński and Hąc-Wydro 2014;Johnston et al 2019), and difficulty in quantifying responses to growth-regulator herbicides. The relatively low level of dicamba resistance, coupled with the heretofore mentioned challenges, limits the conclusions that can be drawn about the inheritance of the trait.…”

Investigation of physiological and molecular mechanisms conferring diurnal variation in auxinic herbicide efficacy

“…Variation in auxinic herbicide efficacy across time of application has been observed, displaying the classical trend of reduced phytotoxicity near dawn and/or dusk that has been reported with other herbicides [16,22,23]. This has been specifically observed in A. palmeri under controlled laboratory conditions [24]. Coupled with the aforementioned growth and reproductive characteristics in Amaranthus spp., it can thus be conceived that it is only a matter of time until widespread selection for auxinic herbicideresistant alleles are realized in Amaranthus spp.…”

“…This has been specifically observed in A . palmeri under controlled laboratory conditions [ 24 ]. Coupled with the aforementioned growth and reproductive characteristics in Amaranthus spp., it can thus be conceived that it is only a matter of time until widespread selection for auxinic herbicide-resistant alleles are realized in Amaranthus spp.…”

Design, Synthesis, and Biological Activity Determination of Novel Phenylpyrazole Protoporphyrinogen Oxidase Inhibitor Herbicides Containing Five-Membered Heterocycles

“…There are a wide variety and a large number of weeds worldwide, most of which pose a threat to agricultural production, leading to a significant reduction in food crop yields and becoming one of the important factors affecting agricultural production. , Although the first generation of herbicides promoted the process of agricultural production, the widespread use of herbicides, especially the repeated use of single herbicides or herbicides with the same mechanism of action, has led to a series of difficult to overcome problems, such as phytotoxicity, − pesticide residues, − the emergence of resistant weeds, − and the adverse impact on ecological environments such as water sources and soil, and even posed a threat to human health. − The emergence of a series of problems has posed more severe challenges to the development of chemical herbicides. Therefore, the development of new herbicides requires not only the advantages of target specificity, high efficiency, and strong targeting but also the characteristics of low toxicity, low pollution, low usage rate, and environmental friendliness. − …”