Control of Italian ryegrass and Alexandergrass in corn using different corn sowing date, pre- and post-emergent herbicides

Abstract

Glyphosate-resistant (GR) Italian ryegrass (LOLMU) and Alexandergrass (URPLA) are troublesome weeds in corn cropping systems in Southern Brazil. The emergence pattern of those weeds is not uniform and may change according to the season's environmental characteristics. Also, herbicide resistance has been diminishing the success of the weed control programs. The objectives of this study were to evaluate the influence of corn-sowing date on LOLMU and URPLA densities and their control provided by pre-and post-emergent herbicides. Field trials were conducted in two crop seasons in Southern Brazil consisting of three corn sowing date (August, September, and October) and the application of atrazine + S-metolachlor (residual) in corn pre-emergence in different post-emergence weed control programs with glyphosate, ammonium-glufosinate, nicosulfuron, and atrazine. The results indicated that the sowing date had a significant influence on LOLMU and URPLA densities.Corn sown in the earliest period was exposed to a higher LOLMU density, whereas corn sown in the latest period had a higher density of URPLA. Also, the application of residual herbicide at corn pre-emergence reduced both weed species densities and decreased the pressure for the control of glyphosate-resistant LOLMU for the post-emergence herbicides. The use of residual herbicides in corn pre-emergence is an efficient strategy to be considered in the LOLMU and URPLA control programs, followed by post-emergence application of glyphosate, ammonium-glufosinate, atrazine, and nicosulfuron.

Integrated weed management strategies in a long-term crop rotation system

“…Characteristics after glyphosate + atrazine treatment on corn. Important factors about it should be the earlier corn season compared with soybean and pre-emergence herbicide implementation, once atrazine is an essential and an efficient alternative in corn with direct effects on weeds' seed bank species as Lolium (Beckie et al, 2020;Piasecki et al, 2020;Barroso et al, 2021). Besides it, long-term and repeated pre-emergence herbicides could maintain weed density at a low level (Gao et al, 2019).…”

Morphological responses of maize hybrids under competition with hairy beggarticks

“…Among the various factors responsible for the low average productivity of maize, interference caused by weeds, which compete for water, light, nutrients, and may host pests and diseases, is predominant. Weeds may also release allelopathic substances that interfere with the growth and development of the crop, reducing grain yield (FRANDOLOSO et al, 2019;GHENO et al, 2021;PIASECKI et al, 2020;FREITAS et al, 2021a) or even increasing production costs (HELVIG et al, 2020). Losses in maize grain yield caused by weeds can be greater than 80%, if no management is adopted to control these species (PIASECKI et al, 2020;HELVIG et al, 2020;FREITAS et al, 2021a,b).…”