|Neto, Antonio M.|
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/7/2011
Publication Date: 2/7/2011
Citation: Alonso, D., Constantin, J., Oliveira, R., Koskinen, W.C., Neto, A.O., Hugo, D., Guerral, N. 2011. Carryover potential of herbicides used for Conyza spp. control [abstract]. Weed Science Society of America Meeting Abstracts. No. 4. Interpretive Summary:
Technical Abstract: Conyza spp. is one of the most important weeds in southern Brazil, and has imposed a serious threat to agriculture as the selection of tolerant and resistant biotypes to glyphosate increases. This, in turn, has led to continuous efforts by researchers for management alternatives for this species. This weed’s main emergence flux is in winter, therefore, different winter burndown alternatives have been studied for Conyza biotypes using tank mixtures of glyphosate+2,4-D, with or not with residual soil herbicides. Research was conducted to evaluate soil carryover of residual herbicides that can be used for Conyza winter control. Greenhouse experiments were carried out in pots arranged in a complete randomized block design with 6 replications. Herbicides evaluated in this experiment were metsulfuron, amicarbazone, metribuzin, isoxaflutole, and MSMA. Treatments consisted of soybean sowing (six seeds/pot) at 0, 30, 60, 90, and 120 days after herbicide application (DAA), and soil cover with oat straw or no cover. The only herbicide that killed soybean plants was amicarbazone, either when applied to soil with (up to 60 DAA) or without (up to 120 DAA) straw. All other herbicides affected growth to some extent. Metribuzin only caused damage when soybean was sowed just after application on covered soil, and until 30 DAA on noncovered soil. Metsulfuron caused shoot dry biomass reduction when sowing was carried out at 60 DAA for both soil treatments. Isoxaflutole affected growth up to 60 DAA in straw covered soil, and 90 DAA for soil without cover. MSMA did not cause negative effects when applied on soil with cover, but caused shoot dry biomass reduction up to 60 DAA on soil without cover. The results suggest that in most cases soil cover decreases the carryover effect. To avoid soybean injury, it is suggested that sowing should be done 90 DAA for MSMA and metsulfuron, and 120 DAA for isoxaflutole and metribuzin. For amicarbazone, a significant carryover effect was found even when soybean was sown 120 DAA.