Herbicide Presistence in Soil

Herbicides are applied directly to soils or plant foliage. Interaction of a herbicide with various living and non-living components of the environment ultimately determines how quickly it dissipates or degrades. Dissipation can be defined as the disappearance or loss of herbicide from the target site through a number of processes. Herbicide may move from the target site via processes such as runoff or leaching, or gradually degrade to undetectable or insignificant levels. Degradation, or alteration of the herbicide molecule by primarily chemical and biological processes, is thus one component of dissipation. Alternatively, we can distinguish between the transfer of herbicide molecules in soil due to processes such as runoff and leaching, and the transformation of the herbicide molecule, due to various degradation pathways. Degradation usually results in deactivation of the herbicide, while herbicide is not deactivated in transfer processes. Processes involved in herbicide dissipation include adsorption, degradation through chemical reaction, microbial degradation, photodecomposition, leaching, runoff, volatilization, and plant uptake

Determining Herbicide Carryover Risk- How Close Can We Come?

Crop injury resulting from herbicide carryover is a function of four variables: 1) the herbicide residue persisting from one year or crop to the next (or the herbicide concentration in soil at the time of planting); 2) the availability of the herbicide for uptake by the germinating seed, emerging seedling, or young plant; 3) the sensitivity of the follow crop to the herbicide; and 4) the environmental conditions in the early part of the growing season. These four factors interact to determine the potential for or the severity of injury due to carryover

Corn Growth Retardation Resulting from Soybean Herbicide Residues

Author Institution: Department of Agronomy, The Ohio State UniversityImazaquin (trademark Scepter) is a weed control herbicide that was used on 15 and 37% of Ohio's 1987 and 1988 soybean acreage, respectively. Drought conditions in 1987 retarded the microbiological decomposition of imazaquin, resulting in carryover that damaged corn {Zea mays L.) grown in those fields so treated. Ohio's farmers were concerned that the more severe 1988 drought would cause even more herbicide carryover, jeopardizing their 1989 corn corp. In early 1989, imazethapyr (trade name Pursuit), another soybean herbicide chemically similar to imazaquin, received federal registration for use in the 1989 soybean crop

Biology and management of common ragweed

"This publication examines the biological characteristics of common ragweed that make it a troublesome weed, and outlines management practices that will help growers better manage the weed and slow the selection of biotypes with herbicide resistance."--Extension website, viewed October 31, 2022.Reviewed by Kevin Bradley (Division of Plant Sciences), Tom Jordan (Purdue University), Glenn Nice (Purdue University), Reid Smeda (University of Missouri), Christy Sprague (Michigan State University), Mark Loux (Ohio State University), Bill Johnson (Purdue University)Reviewed 10/22Includes bibliographical reference

Biology and management of horseweed

"This publication discusses some of the biological characteristics that make horseweed particularly troublesome to control in agronomic crops. Then it provides management strategies, using technologies now available, that will allow growers to control herbicide-resistant horseweed and hopefully slow the spread of glyphosate resistance."--Extension website, viewed October 31, 2022.Reviewed by Kevin Bradley (Division of Plant Sciences), Mark Loux (Ohio State University), Jeff Stachler (Ohio State University), Bill Johnson (Purdue University), Glenn Nice (Purdue University), Vince Davis (Purdue University), Dawn Nordby (University of Illinois)Reviewed 10/22Includes bibliographical reference

Biology and management of giant ragweed

"This publication discusses the biological characteristics that make giant ragweed troublesome, and provides management guidelines that will minimize yield losses and slow the development of glyphosate-resistant biotypes."--Extension website, viewed October, 31, 2022.Reviewed by Kevin Bradley (Division of Plant Sciences), Bill Johnson (Purdue University), Mark Loux (Ohio State University), Dawn Nordby (University of Illinois), Christy Sprague (Michigan State University), Glenn Nice (Purdue University), Andy Westhoven (Purdue University), Jeff Stachler (Ohio State University)Reviewed 10/22Includes bibliographical reference

Seedbank Persistence of Palmer Amaranth (\u3ci\u3eAmaranthus palmeri\u3c/i\u3e) and Waterhemp (\u3ci\u3eAmaranthus tuberculatus\u3c/i\u3e) across Diverse Geographical Regions in the United States

Knowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeri S. Watson) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems

The silver bullet that wasn’t: Rapid agronomic weed adaptations to glyphosate in North America

The rapid adoption of glyphosate-resistant crops at the end of the 20th century caused a simplification of weed management that relied heavily on glyphosate for weed control. However, the effectiveness of glyphosate has diminished. A greater understanding of trends related to glyphosate use will shed new light on weed adaptation to a product that transformed global agriculture. Objectives were to (1) quantify the change in weed control efficacy from postemergence (POST) glyphosate use on troublesome weeds in corn and soybean and (2) determine the extent to which glyphosate preceded by a preemergence (PRE) improved the efficacy and consistency of weed control compared to glyphosate alone. Herbicide evaluation trials from 24 institutions across the United States of America and Canada from 1996 to 2021 were compiled into a single database. Two subsets were created; one with glyphosate applied POST, and the other with a PRE herbicide followed by glyphosate applied POST. Within each subset, mean and variance of control ratings for seven problem weed species were regressed over time for nine US states and one Canadian province. Mean control with POST glyphosate alone decreased over time while variability in control increased. Glyphosate preceded by a labeled PRE herbicide showed little change in mean control or variability in control over time. These results illustrate the rapid adaptation of agronomically important weed species to the paradigm-shifting product glyphosate. Including more diversity in weed management systems is essential to slowing weed adaptation and prolonging the usefulness of existing and future technologies

Determining Herbicide Carryover Risk- How Close Can We Come?

Crop injury resulting from herbicide carryover is a function of four variables: 1) the herbicide residue persisting from one year or crop to the next (or the herbicide concentration in soil at the time of planting); 2) the availability of the herbicide for uptake by the germinating seed, emerging seedling, or young plant; 3) the sensitivity of the follow crop to the herbicide; and 4) the environmental conditions in the early part of the growing season. These four factors interact to determine the potential for or the severity of injury due to carryover.</p

Herbicide Presistence in Soil

Herbicides are applied directly to soils or plant foliage. Interaction of a herbicide with various living and non-living components of the environment ultimately determines how quickly it dissipates or degrades. Dissipation can be defined as the disappearance or loss of herbicide from the target site through a number of processes. Herbicide may move from the target site via processes such as runoff or leaching, or gradually degrade to undetectable or insignificant levels. Degradation, or alteration of the herbicide molecule by primarily chemical and biological processes, is thus one component of dissipation. Alternatively, we can distinguish between the transfer of herbicide molecules in soil due to processes such as runoff and leaching, and the transformation of the herbicide molecule, due to various degradation pathways. Degradation usually results in deactivation of the herbicide, while herbicide is not deactivated in transfer processes. Processes involved in herbicide dissipation include adsorption, degradation through chemical reaction, microbial degradation, photodecomposition, leaching, runoff, volatilization, and plant uptake.</p