Use of strobilurin in mulberry crop to improve silkworm coccon production

• Grant number: 14/25673-0
• Support type: Regular Research Grants
• Duration: April 01, 2015 - March 31, 2017
• Field of knowledge: Agronomical Sciences - Animal Husbandry
• Principal Investigator: Daniel Nicodemo
• Grantee: Daniel Nicodemo
• Home Institution: Faculdade de Ciências Agrárias e Tecnológicas. Universidade Estadual Paulista (UNESP). Campus de Dracena. Dracena, SP, Brazil

Abstract

Coccon production by silkworm (Bombyx mori) is highly influenced for the quantity and quality of mulberry leaves (Morus spp.) offered to the caterpillars. However, the amount of leaves produced by each plant is inversely proporcional to its nutritrional quality. Therefore, it is preconized that mulberry branches must be offered to the caterpillars 90 days after the last cutting of the branch, even with significant decrease of nutritional quality of the leaves on the last weeks of plants development. The pyraclostrobin is a fungicide which has been used to delay senescence and oxidative stress of many crops, contributing also to virus attack resistance. The aim of this work is to verify whether the treatment of mulberry plants with pyraclostrobin contributes to the retardation in quality decline of mulberry leaves and to improve cocoon production and silk thread quality. In three seasons (summer, autumn and spring), during 2015 and 2016, we will use a mulberry crop (IZ56/4 variety) treated with pyraclostrobin (0, 100, 200 and 300 g / ha of active ingredient), applied on a solution of 1000 L / ha, after 60 and 75 days of each pruning of mulberry branches. It will be verified the chlorophyll content of mulberry leaves, leaf production and its levels of macro and micronutrients.Regarding silkworm caterpillars on fifth instar fed on mulberry leaves of plants treated with pyraclostrobin, it will be evaluated the leaf consumption, mortality of caterpillars, fungal contamination in the rearing bed, susceptibility to BmNPV and mitochondrial bioenergetics "in vivo" and "in vitro" of the head and midgut of silkworm caterpillars. With the obtained cocoons, it will be verified the percentage of defective coccons and the raw and net silk contents. For silk threads, it will be evalueted its mechanical characteristics, including analysis of X-ray diffraction and Energy Dispersive Spectroscopy. The data will be submitted to analysis of variance and for multiple comparisons will be applied the 5% Tukey test, except to the mitochondrial bioenergetics data, for which will be analyzed the contrasts to evaluate the polynomial effect of the doses on the variable studied, followed by Dunnett's test. (AU)