Fitotoxicidade causada por deriva simulada dos herbicidas chlorimuron ethyl e tembotrione na cultura da batata

Abstract

Potato development (Solanum tuberosum subs. tuberosum) is affected by a large number of factors, both biotic and abiotic, that can influence its growth, development and productivity. Considering that many potato production areas are located close to other crops, such as maize and soybeans, the use of herbicides in these crops can affect potatoes through drift. Therefore, this study determined phytotoxicity symptoms and quantified losses in yield and quality of potato tubers in response to sub-doses of herbicides chlorimuron ethyl and tembotrione, simulating drift. Planting of cultivar Asterix was done on April 15, 2013, in the region of Perdizes-MG. Independent experiments were done for each herbicide, chlorimuron ethyl and tembotrione. in randomized blocks design with four replications. Treatments included three sub-doses of each herbicide under (2.5%, 5.0%, or 10.0% of the maximum recommended dose), a control treatment, which was considered 100% of this dose, applied in two different times at 37 and 60 days after planting, and an untreated treatment without herbicide. In each experiment, herbicide solution with chlorimuron ethyl or tembotrione was directly sprayed. Plant injury in shoots was evaluated at 3, 13, 17 and 24 DAA (days after application) according to plant vigor with symptoms and characterization through a rating scale of 0 to 10, where 0 was vigorous plant and absence of symptoms and 10 indicated plant death. The average stem length was determined at 24 DAA. At 17 DAA, chlorophyll content, rate of CO2 assimilation, stomatal conductance, transpiration rate and internal carbon from the plant were determined. Harvest was done on August 9, 2013, when productivity, soluble solids content were determined and tubers ranked in diameter and for possible defects and physiological disorders. In the experiment with the herbicide chlorimuron ethyl, the sub-doses of the product caused visual symptoms of phytotoxicity. Also, reduced plant growth of the full spray control treatment was observed in comparison with the untreated treatment. The physiological characteristics were not affected. The herbicide affected productivity and caused cracks in tubers at greater dose when sprayed in early plant development. Spraying plants with the herbicide tembotrione also induced visual symptoms of phytotoxicity, which were different from the full spray control. The full spray control treatment resulted in shorter stems in comparison with the untreated control and 2.5% sub-dose. Rates of CO2 assimilation and transpiration were greater for the untreated control and sub-doses when compared to the full spray control treatment, while internal carbon content was greater in the full spray control. Productivity was affected by doses of 10% and 100% of the recommended dose. The herbicides were toxic on the vegetative growth and tuber yield at greater concentrations.