Deriva simulada de dicamba na cultura do eucalipto

Abstract

With the emergence and spread of weeds resistant to different herbicides, agricultural research companies have been looking for new technologies to control these species. One of the alternatives is the introduction of soybean and cotton cultivars with tolerance to the herbicide dicamba. As a result, this herbicide can be used more often as part of a resistant weed management program. However, the higher commercialization and use of this herbicide, tends to increase the drift risks, since the dicamba molecules have high volatility and can cause damage to non-target plants, located in adjacent areas, even in low doses. The study aimed to evaluate the dicamba underdoses effects, on phytotoxicity, biometric, morpho-anatomical and physiological variables of young eucalyptus plants. The experiment was carried out under field conditions and at the Weed Laboratory of the Instituto Federal Goiano, Campus Rio Verde, GO. The treatments used were: 0 (control); 7,5; 15; 30; 60; 120 and 240 g e.a. ha-1 of dicamba applied 45 days after seedlings planting (DAP) in the field. For the phytotoxicity variable, it was observed that treatment 120 and 240g e.a ha-1 caused bigger damage to eucalyptus plants in all periods of evaluation. The predominant symptoms were: epinasty, increased number of shoots, necrosis and senescence of young branches and leaves. Regarding the variables of height, diameter, branches number and leaves, stem and root dry mass, the herbicide dicamba significantly compromised these variables in the doses of 120 and 240g and ha-1, interfering in the eucalyptus crop growth and development. However, the plants recovered over time. The plant material showed changes in the mesophyll structures at 7 and 14 days after application (DAA) and in the palisade parenchyma at 14 DAA. For abaxial and adaxial epidermis and spongy parenchyma structures, there was no significant difference. The physiological variables underwent changes at 1 and 7 DAA for transpiratory rate, and for the internal and external CO2 concentration and stomatal conductance only at 7 DAA. The levels of Chlorophyll a and b also changed in the evaluation period. There was no statistical difference for the photosynthetic rate. The results indicate that the simulated drift effect of the herbicide dicamba can interfere in the correct development of young eucalyptus plants, which may cause losses in the initial planting phase, causing future losses for producers.