Distribution of glyphosate‐resistant Amaranthus spp. in Nebraska

Abstract

The intensive glyphosate selection pressure exerted in soybean (Glycine max) fields in eastern Nebraska is one of the major factors causing widespread occurrence of glyphosate resistance in common waterhemp in the state. The relatively low frequency of glyphosate-resistant Palmer amaranth in the state highlights the importance of the application timing and the adoption of multiple modes of action in weed management practices to delay the evolution of glyphosate resistance. © 2017 Society of Chemical Industry.

Herbicide drift exposure leads to reduced herbicide sensitivity in Amaranthus spp.

“…Both are obligate outcrossing dioecious weed species with a fast growth habitat, extended emergence window, and prolific seed production with high genetic plasticity which pose a challenge to their management 37-44 . Numerous Palmer amaranth and waterhemp populations have evolved resistance to herbicides that target 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), 4-hydroxyphenylpyruvate dioxygenase (HPPD), photosystem II, protoporphyrinogen oxidase (PPO), auxin receptors, microtubule assembly, and acetolacte synthase (ALS) in the US 15,17,[45][46][47][48][49][50][51][52][53][54] . Moreover, pollen mediated gene flow has been reported as a major contributor to herbicide resistance dissemination in Palmer amaranth and waterhemp in the US Midwest 55,56 .Although controlling weed populations on field margins and ditches is considered a best management practice to delay herbicide resistance evolution, these weed populations are often neglected in agricultural landscapes [15][16][17]29 .…”

“…Although controlling weed populations on field margins and ditches is considered a best management practice to delay herbicide resistance evolution, these weed populations are often neglected in agricultural landscapes [15][16][17]29 . The hypothesis of this study is that repeated herbicide drift in field borders and ditches can select weed biotypes with reduced herbicide sensitivity.…”

“…Wats.) are often abundant in field margins and ditches throughout the US [15][16][17] . Herbicide drift exposure could be detrimental to long-term weed management as numerous weed species have evolved herbicide resistance following recurrent applications of low herbicide rates [18][19][20][21][22][23][24][25][26][27][28] , and we reported in a previous study that spray drift can expose weeds to herbicide doses associated with herbicide resistance selection 14 .…”

“…Herbicide drift exposure could be detrimental to long-term weed management as numerous weed species have evolved herbicide resistance following recurrent applications of low herbicide rates [18][19][20][21][22][23][24][25][26][27][28] , and we reported in a previous study that spray drift can expose weeds to herbicide doses associated with herbicide resistance selection 14 . In addition, herbicide resistance has been widely reported in weed populations inhabiting field margins and ditches surrounding agricultural landscapes 15,17,29 .…”

Introduction to Pest Management Science special issue for GHRC 2017

“…This Special Issue also includes articles related to improving our understanding of herbicide resistance frequency, management, and education. Resistance is considered at regional scales for surveys, modeling and management, and farmer perspectives . The role of ecological weed management in addressing herbicide resistance is reviewed .…”