Salt and temperature effects on sethoxydim spray deposit and efficacy

Certain salts in the spray carrier can antagonize sethoxydim, while other s alts overcome the antagonism or increase the herbicide's efficacy. Sethoxyd im responses to salts have not been consistent, and the inconsistency is no t completely understood. Experiments were conducted in the greenhouse to de termine sethoxydim phytotoxicity to oat as influenced by salts in the spray carrier and by air temperature at and immediately after application as the y alter the spray deposit characteristics. Thick amorphous spray deposits w ere related to ineffective sethoxydim-petroleum oil adjuvant treatments app lied alone at 10 C or with bentazon at 10 or 25 C. Also, thin deposits with salt residues were related to ineffective sethoxydim treatments, as when s odium bicarbonate was present. Ammonium sulfate reduced or overcame antagon ism of sethoxydim phytotoxicity caused by low temperature, bentazon, and so dium bicarbonate and gave thin deposits having close contact with the leaf epicuticular surface but without obvious salt deposits. UV light antagonism of sethoxydim phytotoxicity was different depending on temperature at and shortly after application and depending on salts in the spray mixture. The results indicate that salts in a bentazon spray carrier are in part antagon istic because of their effect on final spray deposit.