A post-emergence herbicide program for weedy sunflower (Helianthus annuus L.) control in maize

During the last 15 years in Serbia, there has been an invasion of H. annuus across the country. Plants were initially limited to non-cultivated areas near arable fields, while in recent years the species has started to occur and establish populations in crop fields, especially into wide-row crops. We tested eight herbicides in two greenhouse experiments: 1) a dose-response study; 2) an efficacy study with reduced herbicide rates adding an adjuvant. The tested herbicides showed satisfactory weed control, where all estimated effective doses 90 (ED90) were lower than the recommended field rate for each herbicide, except for dicamba. The addition of non-ionic surfactants significantly increased the efficacy of glyphosate, mesotrione, rimsulfuron, and foramsulfuron. Whereas, there was no clear advantage to adding an adjuvant to bentazone and tembotrione, as the H. annuus population was already very sensitive (plants died in 1/8 of recommended rate in a dose-response study). All tested herbicides, except dicamba, can be used for satisfactory H. annuus control in maize, while glyphosate can be used for control of the species in non-agricultural lands.