Juvenile hormone analogues (JHA) have been tested as growth regulators of Bombyx mori L., aiming to increase the cocoon production. These chemicals, when applied in appropriate doses, promote prolongation of the larval period. The effects of JHA application may vary with the product, strain, and time of application. The objective of this study was to evaluate the topical application in different times of three JHA and their effects on larval growth and silk production of the Brazilian silkworm strain C115xN108. Pyriproxyfen, methoprene and fenoxycarb were applied on silkworm larvae at 24h, 48h, 72h or 96h after the beginning of the fifth instar (HFI) and the effects of the products on larval and adult biological characters and silk production were evaluated. Independently of the time of application, the three products affected all the evaluated parameters. The nutrients stored during the extended period by the treated insects were used for growing the silk glands and were converted in corporal weight, with consequent increments in the silk production. Applications of piryproxyfen, methoprene and fenoxycarb between 48 and 72 HFI promoted, in a general way, the largest increments in the biomass and cocoon production of B. mori. Variations in the time of application between 24 and 96 HFI did not influence adult emergence, oviposition or the egg viability of B. mori.
Fenoxycarb; methoprene; pyriproxyfen; insect growth regulators; cocoon production
