RESPOSTA DE BIÓTIPOS DE CAPIM-PÉ-DE-GALINHA A HERBICIDAS E SUA DISCRIMINAÇÃO VIA SENSORIAMENTO REMOTO

Abstract

Goosegrass (Eleusine indica) stands out as one of the main weeds in the Cerrado agricultural scenario, with increasing reports of multiple resistance. Conventional methods for identifying resistance are highly time-consuming. This study aimed to evaluate the use of thermographic remote sensing as an indicator of susceptibility and resistance in E. indica biotypes subjected to EPSPs and ACCase-inhibiting herbicides. For this purpose, seeds were collected from populations where growers reported control escapes in the field, as well as seeds from a known susceptible biotype. The experiment was conducted in a completely randomized design (CRD). First, a dose-response curve study was performed to confirm the susceptibility and resistance status of the three evaluated biotypes (Figueiredo: susceptible; Moresco and Barbosa: resistant). Subsequently, the effect of six treatments was evaluated (T1: Control; T2: Glyphosate; T3: Clethodim; T4: Haloxyfop; T5: Glyphosate+Clethodim; T6: Glyphosate+Haloxyfop), with 5 replications. At 17 days after application (DAA), the average leaf temperature was measured using a multispectral camera (Flir C2 thermal camera), determining the thermal contrast (Delta T = Mtreatment - Mcontrol), in addition to visual control and final dry mass. The results demonstrated that, in the resistant biotypes, the leaf temperature resembled that of the control, undergoing little thermal variation. On the other hand, in the susceptible biotype, the plant temperature increased by up to +3.37 °C. The Barbosa biotype showed severe resistance to haloxyfop (8.2% control) and glyphosate (28%), maintaining stomatal thermal stability (Delta T of +0.29 °C and +0.07 °C, respectively). The Figueiredo biotype demonstrated high passive thermal stress under glyphosate and haloxyfop (Delta T of +3.30 °C and +3.37 °C, respectively), evidencing transpirational blockage due to cell death. In turn, the Moresco biotype evidenced intermediate multiple resistance behavior to glyphosate (51% control) and haloxyfop (52%), with moderate thermal stress (Delta T of +1.49 °C and +0.50 °C, respectively). Clethodim expressed a slow and gradual thermal response in all populations (Delta T less than or equal to +0.89 °C), temporarily preserving transpiration. It is concluded that leaf thermal contrast is an early, accurate, and non-destructive indicator, effective for safely discriminating the level of resistance of biotypes in the field before the onset of visual symptoms.