RESPONSE OF MSMA-RESISTANT AND MSMA-SUSCEPTIBLE COMMON COCKLEBUR (XANTHIUM-STRUMARIUM) BIOTYPES TO COTTON (GOSSYPIUM-HIRSUTUM) HERBICIDES AND CROSS-RESISTANCE TO ARSENICALS AND MEMBRANE DISRUPTORS

Experiments were conducted to evaluate PRE and POST cotton herbicides for control of MSMA-resistant (R) and -susceptible (S) common cocklebu r biotypes, and to determine potential cross-resistance of the R bioty pe to other arsenical and membrane disrupter herbicides, Cyanazine and clomazone applied PRE were the most effective herbicides for control of R populations. Lactofen or cyanazine in combination with MSMA contr olled R and S biotypes better than fluometuron or pyrithiobac combined with MSMA. MSMA-resistant common cocklebur was not cross-resistant to other arsenical herbicides. Significant differences in cellular elect rolyte leakage and chlorophyll content of the treated leaf between bio types were not evident for paraquat, acifluorfen, and MSMA.