Curvas de dose-resposta de herbicidas aplicados em pré-emergência de Euphorbia hyssopifolia L.

Abstract

The species Euphorbia hyssopifolia L. belongs to the genus Euphorbia and the familyEuphorbiaceae, occurring in pasture areas, roadsides, and sugarcane fields. Consequently, it can interfere with agricultural production and thus needs to be managed. Herbicides' mechanism of action is based on a series of events triggered by the initial action of the herbicide, which eliminates the weed. Chemical control with herbicides is the most commonly used tool in various crops, but information on the susceptibility of all species in a particular area is lacking. The key to solving this problem lies in constructing dose-response curves with herbicides commonly registered for crops. Therefore, this study aims to use dose-response curves with herbicides widely used in sugarcane culture belonging to the mechanisms of action of ALS inhibitors (acetolactate synthase enzyme), carotenoid biosynthesis inhibitors, photosystem II inhibitors (PS II), cellulose biosynthesis inhibitors, and protox inhibitors (protoporphyrinogen Oxidase enzyme) for E. hyssopifolia control. The experiments were conducted in the greenhouse of the Engineering and Agricultural Sciences Campus of the Federal University of Alagoas, with pre-emergence application of diclosulam, imazapic, metsulfuron-methyl, clomazone, isoxaflutole, indaziflam, hexazinone, tebuthiuron, amicarbazone, flumioxazin, oxyfluorfen, and sulfentrazone herbicides at increasing doses of: 0; 12.5; 25; 50; 100; 200; and 400% of the recommended dose for sugarcane cultivation. Seeds were sown in 500 mL capacity cups, and then herbicide treatments were applied. The application of the pre- emergence treatments of E. hyssopifolia were using a CO2 backpack sprayer equipped with bars containing two Adia 110 flat jet spray nozzles, with a constant pressure of 200 KPa, to provide a spray volume corresponding to 120 L.ha-1 . Visual control assessment was performed, where 0% represented total absence of symptoms and 100% represented the plant death, and at the end of the experiments, plant samples were collected for aerial dry mass. As a result of the study, E. hyssopifolia showed greater sensitivity to diclosulam, imazapic, metsulfuron-methyl, clomazone, hexazinone, indaziflam, flumioxazin, and oxyfluorfen herbicides, as lethality occurred at doses below 20% of the commercial indicated dose for sugarcane cultivation. For isoxaflutole, tebuthiuron, amicarbazone, and sulfentrazone herbicides, the species exhibited lower sensitivity, with a lethal dose recorded above 50% of the respective recommended commercial dose. Keywords: chemical control, hyssopleaf sandmat, susceptibility, mechanism of action.