Over the past 3 years, tall waterhemp (Amaranthus tuberculatus Moq. Sauer) resistance to 4-hydroxyphenyl-pyruvate dioxygenase (HPPD) inhibiting herbicides has been confirmed in Illinois, Iowa, and Nebraska seed corn production fields. Resistance to HPPD-inhibiting herbicides in Palmer amaranth (A. palmeri S. Wats.) has also been reported in Kansas. These populations are also resistant to other herbicides with different mechanisms of action (e.g., atrazine), and can therefore, be considered multiple-herbicide resistant populations. The existence of these HPPD-resistant populations illustrates the propensity of different species within this genus, to evolve resistance to HPPD-inhibitors, in addition to other mechanisms of action. The evolution of HPPD-inhibitor resistance in these seed corn production fields has been attributed to the limited diversity of cultural practices and of mechanisms of action of herbicides used, necessitated by the sensitivity of inbred lines to herbicides that are more widely available for use in field corn production. Nevertheless, this development is an early warning of potentially more widespread occurrences. In common with resistance in other herbicides, the risk of HPPD-resistance development is high if there is reliance on the exclusive use of HPPD-inhibiting herbicides for weed control, particularly in species with high genetic diversity and which are obligate out-crossers, such as A. tuberculatus or A. palmeri, in which resistance to other herbicide mechanisms of action has already evolved. Considerable resources have been employed in research to understand the mechanism of resistance and to assess the probability of evolution of further resistance to HPPD-inhibitors in waterhemp. In addition, research continues to explore the options for managing this issue from both proactive and solution-based approaches, in corn and soybean production systems. A diverse approach, which includes the use of multiple mechanisms of action and other methods of weed management, is critical to the sustainable use of HPPD-inhibiting herbicides.

HPPD-inhibitor herbicide resistance in the USA: A Syngenta perspective

246th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.