Radiação UV-C no controle de Tetranychus Urticae (Ácaro rajado) na cultura do morangueiro

Abstract

The culture of strawberry (fragaria x ananassa) has conquered much space in the Brazilian market, this occurs by the high acceptance of the Brazilian and world population, by the consumption of this pseudofruit is in natura, in short majority. The market trend has been the production in protected environments, a condition that allows increased productivity, however, with some disadvantages. Among them, due to high temperature and low humidity, the incidence of Tetranychus urticae (spider mite) is favored in this type of cultivation, being considered the main pest of the strawberry crop. The main form of control, currently, is the application of pesticides, a management with high persistence and high risk of environmental contamination. UVC radiation (254 nm) has proven to be an efficient alternative to the use of pesticides because it has a germicidal effect. Therefore, by being able to kill several phytopathogenic organisms, such as fungi, bacteria, protozoa and arthropods, it shows itself as a possibility to control Tetranychus urticae. This technology has the advantage of not leaving residues in the environment, therefore being a good alternative for systems that limit or prohibit the use of pesticides. Thus, we sought to evaluate the field efficiency of UV-C radiation in the control of T. urticae in strawberry crop, emitted by a 55 watt UV lamp. The experiment was carried out in a commercial strawberry production and consisted of making applications of UV-C radiation, through an equipment developed for the research. Four treatments were used: T0 - did not receive radiation; T1 - applications every 24h, cumulative dose: 1.925 kJ m²; T2 - applications every 48h, cumulative dose: 1.1 kJ m²; T3 - applications every 72h, cumulative dose: 0.825 kJ m². Based on the treatments, the spider mite populations were evaluated, as well as the coloration of the trifoliants as a function of the cumulative effect of UV-C radiation. The results point out that there were significant differences among treatments regarding the control of T. urticae populations, proportionally to the cumulative effect of the highest dose applied. Also, the cumulative effect of UV-C radiation had an effect on the coloration of the trifolium, and the highest cumulative dose was the one that presented darker shades of green, a result that may be somehow related to the resistance of the plant to pathogens. Thus, it is possible to infer that UV-C light reduces the populations of spider mite and triggers the increase of pigmenting compounds in the leaves. Treatment 1 (daily applications), equivalent to 1.925 kJ m² of accumulated radiation, showed a 68.9% reduction in the number of mites than the control, as well as promoting the darkening of the trifolium.