Control of barnyardgrass susceptible and resistant to imidazolinones at different temperature regimes before and after imazethapyr application

ABSTRACT Environmental conditions can influence herbicide metabolism and interfere with the evolution of weed resistance. This study aimed to evaluate effect thermal regimes on control barnyardgrass (Echinochloa crus-galli) susceptible resistant herbicides imidazolinones chemical group. Factor A (biotypes) consisted one biotype that is imazethapyr; factor B (dose) comprised six imazethapyr doses between 0 800 g ha-1 for 100 biotype; C (temperature) four (16/16 ºC, 25/25 16/25 ºC 25/16 ºC) which plants were submitted before after application. Concerning biotype, highest levels observed in temperature fuctuation, especially at ºC. At recommended dose (100 ha-1), resulted a level over 90 % less than 50 16/16 biotype. The shoot dry mass was reduced by more 80 30 are subjected pre- post-application period resistance barnyardgrass.