Efeito da aplicação de silicato de cálcio e magnésio no desenvolvimento biológico de Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) em milho (Zea mays) (Poaceae)

Abstract

The study was conducted to evaluate the effect of different doses of silicon, applied to the soil, in biological development of Spodoptera frugiperda (J. E. Smith, 1979) (Lepdoptera: Noctuidae). It was developed in two phases, the first one in a greenhouse and Laboratory of Entomology and the second one in a field, both at the Centre of Agricultural Sciences of Universidade Federal de Alagoas, Rio Largo, AL. The design experiment was completely randomized in blocks at random, for the first and second stages, respectively. Five were used in both treatments, which were represented by different doses of silicon (without application; 500kg.ha-1 of SiO2; 1.000kg.ha-1 of SiO2; 1.500kg.ha-1 of SiO2 and 2.000kg.ha-1 of SiO2) applied to the soil with calcium silicate and magnesium 10.5% silicon, divided into two applications. The first step tests were performed to evaluate resistance (in greenhouse and in the laboratory), with fisrts instar caterpillars from the creation of maintenance, in the first 24hours after the outbreak. The second step was performed in a total area of 128,5m², divided into four blocks, where we evaluated the injuries caused by the plague in four different seasons (15, 30, 45 and 60 days after plants emergence), the infestation and productivity. To evaluate injury, we used a grading scale proposed by CARVALHO (1970). The note data obtained from four evaluations, were transformed in and the medium subjected to the analysis of variance and compared by Tukey test at a significant level of 5%. For the results it is possible to end what to applications of silicate of calcium and magnesium in pots in house of vegetation, did not interfere in the number of instar and not even in the duration of the phase larval and pupal. However, all the treatments that received silicon interfere positively in the weight and length of caterpillars of S. frugiperda in the very development. The applications of silicate of calcium and magnesium, in furrow in the planting and in covering, do not interfere in the productivity and not even in the insults provoked for S. frugiperda in the culture of the corn. However, it was noticed that the percentage of infestation was small when it was used 500 kg.ha-1 of SiO2, to the 15 and 45 DAE.