Occurrence of herbicide resistant weeds is one of the most challenges faced in the modern agriculture. Spot control with herbicides applied with unmanned aerial vehicle usage (UAV) presents potential as important alternative for rational usage of this input, it can be used for cases which plants are found in specific points in the crop area, for which it is not justified an application in total area. This situation can be common from middle up to end of the crop cycle, principally with escaping plants with resistance and/or difficulties to control, as Amaranthus palmeri. Among principal challenges to develop this kind of application, there is a need regarding low spray volume usage, due low operational capacity of sprayer installed in UAV, maintaining droplet deposition in adequate levels for effective control. Therefore, for spot herbicide applications, there is information demand related to factors that interfere in pesticide application technology. The execution of this research proposal aims to develop UAV usage for spot chemical control of herbicide resistant weeds through nozzle and spray volume selection. The work will be carried out in the Texas A&M University (USA), from 1st September up to 30th November 2021. The experiment will be installed in randomized blocks with 4 replications, in an area with occurrence historic of glyphosate resistant weeds, focusing A. palmeri. The treatments will correspond to UAV spot applications using spraying volumes of 10; 12.5 and 15 L/ha, combined to nozzles with different droplet classes: XR 110015 conventional flat fan (fine droplet), TT 110015 impact flat fan (medium to coarse droplet) and AIXR 110015 air induction flat fan (coarse to very coarse droplet). It will also be installed a treatment with a ground boom sprayer and a control without herbicide application, totaling 11 treatments. Water sensitive cards will be randomized placed on adaxial part of the weed leaves for droplet density and deposit cover determination, through digital image analysis of the cards using DepositScan software. The spraying volume deposits per leaf area unit will be obtained with tracer added in spray solution, extracted from weed leaves and quantified through optical density in a visible UV spectrophotometer. Weed control will be evaluated at 7, 14, 21 and 28 days after application (DAA) by percentage visual scale. Weed density and drought mass of aerial part will be measured at 28 DAA. All data will be submitted to variance analysis and means compared by T test (5%). The result will bring information regarding nozzles and spray volumes effect on droplet deposits and weed control efficacy, through spot herbicide application with UAV.
News published in Agência FAPESP Newsletter about the scholarship: