Efficacy of imidazolinone herbicides applied to imidazolinone-resistant maize and their carryover effect on rotational crops

A field study was performed in imidazolinone-resistant maize in order to evaluate the effectiveness and carryover effect on rotational crops of two formulated mixtures of imidazolinone herbicides: imazapyr plus imazapic and imazapyr plus imazethapyr. During the 2003 season the mixtures were applied broadcast to five leaves maize plants at doses of 114 and 228 g ha−1, both tanks mixed with a 31% petroleum hydrocarbon adjuvant at 125 and 250 mL ha−1, respectively. Overall weed control varied from 85%, up to 95%. Weed species controlled were Setaria sp., Chenopodium album, Solanum sp., Amaranthus retroflexus and Digitaria sanguinalis, and Echinochloa cruss-galli whilst Eragrostis sp. was not controlled. Soil activity of the herbicides (carryover) was detected over 10 months after application, imazapyr/imazapic mixture being the most persistent. The sensitivity of rotational crops, from high to low, was the following: Beta vulgaris>Capsicum annum>Lycopersicum esculentum>Cucumis melo>Hordeum vulgare>Medicago sativa>Lolium multiflorum>Avena sativa>Pisum sativum>Allium cepa>Zea mays.