Stress is a widespread phenomenon that all organisms must endure. Common in nature is oxidative stress, which can interrupt cell homeostasis to cause cell damage and may be derived from respiration or from environmental exposure through diet. As a result of the routine exposure from respiration, many organisms can mitigate the effects of oxidative stress, but less is known about responses to oxidative stress from other sources. Helicoverpa armigera is a major agricultural pest moth that causes significant damage to crops worldwide. Here, we examined the effects of oxidative stress on H. armigera by chronically exposing individuals to paraquat—a free radical producer—and measuring changes in development (weight, developmental rate, lifespan), and gene expression. We found that oxidative stress strongly affected development in H. armigera, with stressed samples spending more time as caterpillars than control samples (>24 vs. ~15 days, respectively) and therefore living longer overall. We found 1,618 up‐ and 761 down‐regulated genes, respectively, in stressed versus control samples. In the up‐regulated gene set, was an over‐representation of biological processes related to cuticle and chitin development, glycine metabolism, and oxidation–reduction. Oxidative stress clearly impacts physiology and biochemistry in H. armigera and the interesting finding of an extended lifespan in stressed individuals could demonstrate hormesis, the phenomenon whereby toxic compounds can actually be beneficial at low doses. Collectively, our findings provide new insights into physiological and gene expression responses to oxidative stress in invertebrates.

Since 2016, the fall armyworm (Spodoptera frugiperda, J.E. Smith) has spread from the Americas to invade many regions of the world, including Australia in early 2020. The development of effective pest management strategies for S. frugiperda is a high priority for crop protection. In the invasive range, the degree to which endemic biological control agents can constrain S. frugiperda remains sparsely investigated. This study examines 11 isolates of fungi including six Beauveria isolates and five Metarhizium isolates from Oceania for their potential as S. frugiperda biocontrol. Two Beauveria isolates (B-0571, B-1311) exhibited high virulence toward S. frugiperda caterpillars and adults. The overall mortalities over seven days in 3rd and 6th instar caterpillars and moths (respectively) for B-0571 was 82.81±5.75, 61.46±6.83, and 93.75±3.61, and for B-1311 was 73.72±2.51, 71.88±5.41, and 97.92±2.08%. The majority of deaths in the caterpillars occurred within the first 24 hours (3rd instar control 0.74±0.33%, B-0571 73.96±7.85 and B-1311 62.08±3.67%; 6th instar control 0%, B-0571 66.67±11.02% and B-1311 62.5±9.55%). Infection from both isolates fully prevented reproduction in surviving S. frugiperda females. The two isolates, however, cause a significantly lower mortality in a native noctuidae species: Helicoverpa armigera (3rd instar B-0571 44.79±4.54% and B-1311 19.80±7.51%). The discovery of two fungal isolates with high virulence to S. frugiperda caterpillars and adults opens new avenues for the development of biological control tools for this invasive moth pest. Such tools may also provide additional options for control of native pest lepidoptera, and reduce selection pressure for resistance to Bt and synthetic insecticides.

Stress is a widespread phenomenon that all organisms must endure. Common in nature is oxidative stress, which can interrupt cell homeostasis to cause cell damage and may be derived from respiration or from environmental exposure thought diet. As a result of the routine exposure from respiration, many organisms can mitigate the effects of oxidative stress, but less is known about responses to oxidative stress from other sources. Helicoverpa armigera is a major agricultural pest moth that causes significant damage to crops worldwide.Here, we examined the effects of oxidative stress on H. armigera by chronically exposing individuals to paraquat -a free radical producer -and measuring changes in development (weight, developmental rate, lifespan), and gene expression.We found that oxidative stress strongly affected development in H. armigera, with stressed samples spending more time as caterpillars than control samples (>24 vs. ~15 days, respectively) and living longer overall. We found 1,618 up-and 761 down-regulated genes, respectively, in stressed vs. control samples. In the up-regulated gene set were genes associated with cell senescence and apoptosis and an over-representation of biological processes related to cuticle and chitin development, glycine metabolism, and oxidationreduction.Oxidative stress clearly impacts physiology and biochemistry in H. armigera and the interesting finding of an extended lifespan in stressed individuals could demonstrate hormesis, the process whereby toxic compounds can actually be beneficial at low doses. Collectively, our findings provide new insights into genomic responses to oxidative stress in invertebrates.

Telomeres are repetitive sequences located at the end of chromosomes in eukaryotes that protect against loss of important sequences during the cell replication process. Telomere length (TL) shortens with every round of cell division. When a telomere becomes too short, cells can no longer proliferate and this triggers the cell apoptosis process. Apart from cell replication, the length of telomeres can be affected by factors such as sex, genetics, and stress levels. Oxidative stress in particular can cause damage to telomeres and telomere maintenance processes, resulting in TL shortening. This phenomenon occurs in humans and many vertebrates, especially endothermic species. However, the ways in which various stress types affect the TL of invertebrate species remains ambiguous. Here, we examined the effects of development and oxidative stress on TL in the invertebrate pest moth, Helicoverpa armigera . In the former case, we extracted genomic DNA from three developmental stages (1-day old egg, 4th instar, and first-day emerged moths) and measured TL by qPCR . In the latter, we chronically expos ed individuals to paraquat – an organic herbicide that induces oxidative stress - and then measured TL as per our development methodology . In addition, we examined TL in a subset of published whole genome short-read sequencing data of caterpillars and moths using the software, Computel. In our experimental work, we found that TL in H. armigera was significantly longer at the early stages of development and shortens in later stages. However, oxidative stress does not appear to shorten TL in H. armigera following chronic exposure to paraquat. In our Computel analysis, we found that caterpillars had longer mean TL than moths but this difference was not significant due to the high variation among samples. Collectively, our research provides new data on TL in an underrepresented group, adding new insights into the progression of TL shortening with development and the effects of oxidative stress on TL, while also more generally highlighting the value of applying complementary approaches to TL measurement.