Prickly Sida (Sida spinosa L.) and Cotton Response to Pre- and Early Post-Emergence Herbicides

Prickly sida is a troublesome annual weed native to the USA. It was introduced in Greece over two decades ago and has since been infesting cotton crops, where it proved difficult to control. A two-year field study (2021-2022) was conducted in a cotton field (Karditsa, central Greece) heavily infested with prickly sida to evaluate the efficacy of nine treatments against this weed, using pre-emergence (PRE) and early post-emergence (EPOST) herbicides applied at the field rate. At 8 weeks after treatment, prickly sida control was over 90% with pyrithiobac PRE (68.9 g ai ha(-1)) alone or in mixture with s-metolachlor (960 g ai ha(-1)) or with isoxaben (150 g ai ha-1) and with the application of pyrithiobac + s-metolachlor PRE (34.5 + 960 g ai ha(-1)) followed by pyrithiobac EPOST (34.5 g ai ha(-1)). Flurochloridone + fluometuron PRE (375 + 2000 g ai ha(-1)), flumioxazin + s-metolachlor PRE (50 + 960 g ai ha(-1)), or pendimethalin + terbuthylazine PRE (1500 + 750 g ai ha-1) controlled prickly sida by 89-93% in 2021 and 82-90% in 2022. Pyrithiobac EPOST alone or in mixture with trifloxysulfuron did not adequately control prickly sida. Yield was significantly lower in the weedy check and EPOST compared with the PRE treatments. None of the herbicides caused any visual injury to the crop or any reduction in cotton density. Our results can help in the successful management of prickly sida in non-transgenic cotton to maximize cotton yield and quality.