Effects of an optical brightener on the development, body weight and sex ratio ofSpodoptera frugiperda(Lepidoptera: Noctuidae)

Abstract

The incorporation of stilbene-derived optical brighteners into baculovirus formulations can substantially enhance virus infectivity and persistence of inoculum in the field. We evaluated the effect of the optical brightener Tinopal UNPA-GX (Sigma Chemical Co.) on the weight, development time, adult emergence and sex ratio of the principal pest of maize in the Americas, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Tinopal UNPA-GX was incorporated into semi-synthetic diet at a final concentration of 0.1 or 0.05% (w/v) and larvae of S. frugiperda were individually reared on the Tinopal-treated or an untreated control diet. In both Tinopal treatments, the weights of larvae and pupae were significantly reduced by up to 36 and 13%, respectively. The duration of larval development was increased by up to 30% compared to the controls. Adult emergence was high in all treatments (:/90%) and was not affected by the presence of Tinopal in the diet. Significant differences in the proportion of adult females were observed in the 0.05% Tinopal treatment but not in the control or 0.1% Tinopal treatments. By affecting the integrity of the peritrophic membrane and the rate of sloughing of intestinal epithelial cells, natural pest populations exposed to optical brightener residues from bioinsecticide applications are likely to suffer a reduction in growth rate and other correlates of insect fitness.

Assessment of the suitability of Tinopal as an enhancing adjuvant in formulations of the insect pathogenic fungus Beauveria bassiana (Bals.) Vuillemin

“…Destruction of the peritrophic membrane is also reported to effect physiological functions related to digestion and absorption of nutrients 33. This is reflected in the slowing down of growth and increase in duration of the development cycle of the insect observed in the present study and also reported earlier 21, 33. The increased susceptibility of insects fed on diet with Tinopal may have resulted from the physiological stress experienced by the insects owing to digestional disorders induced by Tinopal.…”

“…Being a stilbene‐derived optical brightener, Tinopal absorbs ultraviolet (UV) radiation and emits visible blue wavelengths 21. Owing to this property, it is reported to bestow photoprotection to microbes when incorporated in the biopesticide formulation.…”

“…Tinopal is reported negatively to affect growth and development of insects and thereby their physiological fitness 21, 34. Destruction of the peritrophic membrane is also reported to effect physiological functions related to digestion and absorption of nutrients 33.…”

“…The effect of three different concentrations of Tinopal (1, 5 and 10 g kg −1 ) on the growth and development of the H. armigera larvae was also investigated to validate its role as a stress‐causing agent. The experiments were done as described by Marti'nez et al 21 The rate of growth was evaluated by measuring larval weight at the end of each instar and the duration of each instar. The long‐term effects of Tinopal were assessed by enumerating the number of adults that emerged, males, females and those with evident malformations.…”

Effect of UV protectants mixed with HaNPV on POBs and larval mortality of Helicoverpa armigera Hübner

“…Optical brighteners such as Tinopal administered in mixtures with occlusion bodies would result in a higher prevalence of covert infection in larvae (Burges and Jones, 1998). Martinez et al (2004) reported that 1 % Tinopal concentration was sufficient to enhance the mortality and hasten the death of Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae. The results revealed that 1 % Tinopal effectively sheltered the POBs from UV degradation and enhanced larval mortality compared to 1 % mango leaf extract 1 % and SNPs.…”