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Published on: September 23, 2021
Beyond the Mortality Effect: Spodoptera frugiperda Multiple Nucleopolyhedrovirus Promotes Changes in Feeding and
Bianca Marina Costa Nascimento1, Anderson Delfino Mauricio Nunes2, Silvio Lisboa de Souza Junior2,3
1Graduate Program in Entomology, Universidade de São Paulo, Campus de Ribeirão Preto, Av. Bandeirantes 3900-Vila Monte Alegre, Ribeirão Preto 14040-900, SP, Brazil.
Abstract:
Infection by Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) profoundly alters the physiology of S. frugiperda (Lepidoptera: Noctuidae), promoting molecular responses that activate genes related to cellular defense. These responses demand substantial energy and lead to feeding dysfunction. Knowledge about the effects of SfMNPV on weight gain and leaf consumption rate is still incipient; in this context, we evaluated the survival rate, weight gain, leaf consumption rate, and body size of S. frugiperda exposed to different concentrations of SfMNPV. A completely randomized design was used in the laboratory. Treatments consisted of SfMNPV from the commercial product Cartugen®, diluted at different concentrations and applied on a Petri dish: 9.00 × 103, 1.80 × 104, 3.75 × 104, 7.50 × 104, 1.35 × 105, 2.25 × 105, and 3.75 × 105 occlusion bodies (OBs)/mL. Fifty first-instar larvae were used per treatment. The median lethal concentration was estimated at 1.32 × 105 OBs/mL (95% confidence interval = 1.22 × 105-1.43 × 105 OBs/mL). Nonlinear regression analysis of sublethal effects showed that the expected weight of the control (W0), the angular parameter (B), and the effective concentration capable of reducing larval weight by 50% (EC50) were 47.40 mg, 1.42, and 1.16 × 104 OBs/mL, respectively. Leaf consumption was inhibited at lower concentrations and increased at higher concentrations among surviving larvae, and larval growth (measured by head diameter, body length, and body width) was lower when larvae were exposed to SfMNPV than in the control. Our data suggest that SfMNPV at low concentrations causes dysfunctions that prevent normal development in surviving individuals, resulting in reduced consumption rate, body growth, and weight gain. Overall, our analysis indicates that the impact of SfMNPV extends beyond mortality; low concentrations can affect larval growth and feeding consumption rate in S. frugiperda.
Insights
Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) infection impacts larval growth and feeding. Even at sublethal concentrations, SfMNPV reduces weight gain and leaf consumption in fall armyworm larvae.
Area of Science:
- Entomology
- Virology
- Insect Pathology
Background:
- Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) infection alters host physiology, inducing cellular defense responses and feeding dysfunction.
- Limited knowledge exists regarding the precise effects of SfMNPV on larval weight gain and consumption rates.
Purpose of the Study:
- To evaluate the impact of varying SfMNPV concentrations on the survival rate, weight gain, leaf consumption rate, and body size of Spodoptera frugiperda larvae.
- To determine the median lethal concentration (LC50) and sublethal effects of SfMNPV on S. frugiperda development.
Main Methods:
- Laboratory experiments using a completely randomized design with S. frugiperda larvae exposed to seven different concentrations of SfMNPV (9.00 × 10³ to 3.75 × 10⁵ OBs/mL).
- Assessment of survival, weight gain, leaf consumption, and body size (head diameter, body length, body width).
- Statistical analysis including median lethal concentration estimation and nonlinear regression for sublethal effects.
Main Results:
- The median lethal concentration (LC50) of SfMNPV was determined to be 1.32 × 10⁵ OBs/mL.
- Sublethal concentrations (EC50) of 1.16 × 10⁴ OBs/mL significantly reduced larval weight.
- Larval growth, including head diameter, body length, and width, was significantly reduced in SfMNPV-exposed larvae compared to controls, even at concentrations below the LC50.
Conclusions:
- SfMNPV infection significantly impacts S. frugiperda survival, with a determined LC50 of 1.32 × 10⁵ OBs/mL.
- Sublethal concentrations of SfMNPV impair larval development, leading to reduced weight gain, body size, and feeding consumption rates in surviving fall armyworm larvae.
- The findings highlight that SfMNPV's detrimental effects extend beyond mortality, influencing the overall fitness and development of S. frugiperda populations.
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