Agrosilício como indutor de resistência: interações entre a cana-de-açúcar, Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) e Cotesia flavipes (Cameron, 1891) (Hymenoptera: Braconidae)

Abstract

The sugar cane plant (Saccharum spp.) spread out by all Brazilian states due to favorable soil and climate conditions of the country and because of its importance to the national economy. However, this culture still faces a number of agronomic issues, including the occurrence of pests and, in particular, the presence of the sugar cane borer Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) that causes reduced production of sugar and alcohol. One of the strategies of Integrated Pest Management (IPM) is the plant's induced resistance to insect pests, and silicon has been shown to induce this resistance. It can also affect the interaction tritrophic natural plant-pest-enemy negatively, demonstrating the incompatibility between the two methods of control, or with positive cumulative effects on reducing pests. The objective of this work was to study the induction of resistance of D. saccharalis in the sugarcane variety of SP791011, from the evaluation of the vegetative growth of the plants fertilized and non-fertilized with different doses of Agrosilício and submitted to artificial infestation of this pest. Another aim of the study was to evaluate the effects of fertilization on the biological and behavioral aspects of D. saccharalis; in addition to observing the effect of silicon on tritrophic interaction D. saccharalis - Cotesia flavipes (Cameron, 1891) (Hymenoptera: Braconidae) - sugarcane. There was an increase in the number of internodes on plants that received the highest doses of Agrosilício while the number of damaged internodes, the Infestation Intensity (% I.I.) and the number of larvae captured decreased on those plants which received highest doses of Agrosilício. The fresh mass of stems and roots and the dry mass of leaves, stems and roots did not differ statistically in relation to doses of Agrosilício. In free choice test and no-choice, for oviposition of D. saccharalis, there was a decrease in the number of eggs as the Agrosilício doses increased. Regarding the parasitism of C. flavipes in larvae of D. saccharalis, the Silicon fertilization did not interfere significantly in the analyzed variables. Parameters of fertility life table showed that the incorporation of powdered stalk of sugarcane fertilized with the highest dose of Agrosilício influenced negatively in the development and reproduction of D. saccharalis. There was no interference in C. flavipes biology reared in sugarcane borer larvae fed on artificial diet containing the powdered stalk of sugarcane fertilized with up to 6.0 t ha-1 Agrosilício.