Two-sex Life Table Theory Research Articles

Sublethal effects of nanoformulated Mentha pulegium L. essential oil on the biological and population growth parameters of the greenhouse whitefly, Trialeurodes vaporariorum, (Hemiptera: Aleyrodidae)

We evaluated the toxicity and sublethal effects of essential oil (Mentha pulegium L.) and its nanoformulation against greenhouse whitefly, Trialeurodes vaporariorum, which is one of the most destructive pests of a wide range of crops. The essential oil was extracted from the plant by steam distillation using a Clevenger apparatus, and 14 chemical components of M. pulegium were identified using gas chromatography-mass spectrometry. The results illustrated that monoterpenoids were main characterized components including pulegone (%66), menthofren (%10.54), 1, 8 Cineole (%8.36), betapenin (%3.49) and limonene (%2.01). The nanoformulation was characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), revealing that the particles were spherical in shape with an average size of 156.40 nm. The leaf dipping was used for the bioassays. The obtained LC50 and LC25 values of treatments indicated that the nanoformulation of essential oil (LC50: 2418.96 and LC25: 1724. 25 ppm) was more toxic than the pure of M. pulegium oil (LC50: 3223.083 and LC25: 779.439 ppm ppm) against greenhouse whitefly adults after 24 h. The life table data were analyzed based on the age-stage, two-sex life table theory using computer program of TWOSEX–MSChart. Also, the sublethal concentration (LC25) of its nanoformulation led to delaying in preadult stage and decreased the adult longevity, and fecundity compared to treatments. Moreover, the sublethal concentration of either M. pulegium oil or its nanoformulation affected the population growth parameters of T.vaporariorum compared to the control. However, the net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), of adults who exposed to the nanoformulation was lower than the pure form of M. pulegium. The overall results demonstrated that the nanoformulation of M. pulegium has the most lethal and sublethal effects on greenhouse whitefly compared with the pure form of essential oil which can be consider in integrated pest management program (IPM) of this pest.

Antibiosis in small grain cereals against the rose-grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae)

Resistance against aphids is an integrated pest management tactic that enhances the economic and environmental sustainability of cereal production. The aim of our study was to assess the degree of antibiosis against Metopolophium dirhodum (Walker) (Hemiptera: Aphididae), one of the most important cereal aphids in temperate regions, in two lines of small grain cereals bred in the Crop Research Institute (CRI) of Prague: spring wheat, Triticum aestivum L. cv. ‘Rufia’, and germplasm of durum wheat, Triticum turgidum ssp. durum (Desf.) van Slageren ‘TTD40363’, under controlled laboratory conditions. Resistant spring wheat cultivar (‘Libertina’) and highly susceptible spring barley (Hordeum vulgare L. cv. ‘Sebastian’) were used for reference. The responses of M. dirhodum to each line and population growth projections were determined according to the age-stage, two-sex life table theory. We found that Rufia was susceptible and TTD40363 was rather resistant to M. dirhodum. The projected population sizes after 35 days were ~ 41,000 individuals in spring wheat Rufia and ~ 12,000 in durum wheat TTD40363, which is within the range delimited by the reference cultivars (4,000 in the highly resistant spring wheat Libertina and 77,500 in highly susceptible spring barley Sebastian). This study provides new data on small grain cereal resistance to aphids. An age-stage, two-sex life table approach was used to assess resistance to aphids on durum wheat and barley for the first time.

Feeding Appropriate Nutrients during the Adult Stage to Promote the Growth and Development of Carposina sasakii Offspring.

Nutrients consumed during the adult stage are a key factor affecting the growth, development, and reproduction of insect offspring and thus could play an important role in insect population research. However, there is absence of conclusive evidence regarding the direct effects of parental (F0) nutritional status on offspring (F1) fitness in insects. Carposina sasakii Matsumura is a serious, widespread fruit-boring pest that negatively impacts orchards and the agricultural economy across East Asia. In this study, life history data of F1 directly descended from F0C. sasakii fed with seven different nutrients (water as control, 5 g·L-1 honey solution, 10 g·L-1 honey solution, 5 g·L-1 sucrose solution, 10 g·L-1 sucrose solution, 15 g·L-1 sucrose solution, and 20 g·L-1 sucrose solution) were collected under laboratory conditions. The growth and development indices, age-stage specific survival rate, age-stage specific fecundity, age-stage specific life expectancy, age-stage specific reproductive value, and population parameters of these offspring were analyzed according to the age-stage, two-sex life table theory. The results showed that the nutritional status of F0 differentially affects the growth, development, and reproduction of F1. The F1 offspring of F0 adult C. sasakii fed with 10 g·L-1 sucrose had significantly higher life table parameters than those of other treatments (intrinsic rate of increase, r = 0.0615 ± 0.0076; finite rate of increase, λ = 1.0634 ± 0.0081; net reproductive rate, R0 = 12.61 ± 3.57); thus, 10 g·L-1 sucrose was more suitable for raising C. sasakii in the laboratory than other treatments. This study not only provides clear evidence for the implications of altering F0 nutritional conditions on the fitness of F1 in insects, but also lays the foundation for the implementation of feeding technologies within the context of a well-conceived laboratory rearing strategy for C. sasakii.

Population-level responses of aphids to pulsed drought stress

The first aim of this study was to test the pulsed stress hypothesis on a system consisting of young spring wheat (Triticum aestivum L.) and the rose-grain aphid Metopolophium dirhodum (Walker) by following the age-stage, two-sex life table theory. This hypothesis predicts that fluid-feeding insects benefit from feeding on plants intermittently stressed by drought due to the increased nutrient availability and restored cell turgor. Our second aim was to illustrate the risk of drawing different conclusions if based on a single or a small subset of parameters or if the entire lifespan of a generation is not covered compared to if the study was conducted at the population level. We applied periods of drought stress (soil water capacity, SWC = 40%) on four occasions relative to the population development of the aphids and compared those treatments with well-watered (SWC = 70%) and continuous stress conditions (SWC = 40%). The timing of the stresses appeared to be important in determining the effect on aphid performance. Although we found some improvement in fecundity when the stress occurred before the aphids were placed on the plants, the overall effect of the early-timed pulsed stress treatments on the rate of increase was negative compared to the well-watered control, which was mainly due to prolonged nymph development. The drought pulse that was timed late (the second week of aphid reproduction) did not show any effect relative to the well-watered control. This study therefore provides no clear support for the validity of the pulsed stress hypothesis.

Demography and Population Projection of Tetranychus urticae (Tetranychidae) on Phaseolus vulgaris (Fabaceae) Colonized by Entomopathogenic Fungal Endophytes.

Tetranychus urticae is a highly polyphagous and global pest. Spider mites primarily feed on the underside of leaves, resulting in decreased photosynthesis, nutritional loss, and the development of chlorotic patches. We investigated the life tables of the two-spotted spider mite T. urticae on fungal endophyte Beauveria bassiana colonized and untreated plants of the common Phaseolus vulgaris L., a bean plant. Based on the age-stage, two-sex life table theory, data were evaluated. The mites raised on untreated plants had protonymphs, deutonymphs, and total pre-adult stage durations that were considerably shorter (1.76, 2.14, and 9.77 d, respectively) than the mites raised on plants that had been colonized (2.02, 2.45, and 10.49 d, respectively). The fecundity (F) varied from 28.01 eggs per female of colonized plants to 57.67 eggs per female of endophyte-untreated plants. The net reproductive rate (R0) in the plants with and without endophytes was 19.26 and 42.53 brood, respectively. The untreated plants had an intrinsic rate of increase (rm) of 0.245 days as opposed to the colonized plants, which had an r of 0.196 days and a finite rate of increase (λ) (1.27 and 1.21, respectively). Population forecasts based on a two-sex, age-stage life table demonstrated the dynamism and variability of the stage structure. Furthermore, the colonization of B. bassiana had a negative impact on the growth and development of T. urticae. It lowered the adult mite life span, female fecundity, net reproduction rate, and intrinsic growth rate. We propose that future research should better use entomopathogenic fungal endophytes to understand host plant resistance strategies in integrated pest management.

Lethal and Sublethal Effects of Cyromazine on the Biology of Musca domestica Based on the Age-Stage, Two-Sex Life Table Theory.

Cyromazine is a triazine insect growth regulator insecticide that is recommended for control of Musca domestica worldwide. Cyromazine is highly effective in causing mortality of M. domestica; however, some aspects of its lethal and sublethal effects on the biology of M. domestica are still unknown. The present study explored lethal and sublethal effects on several biological traits and population parameters of M. domestica. Concentration-response bioassays of cyromazine against third-instar larvae of M. domestica exhibited sublethal and lethal effects from concentrations of 0.03 (LC10), 0.06 (LC25), and 0.14 (LC50) μg/g of a larval medium. Exposure of M. domestica larvae to these concentrations resulted in reduced fecundity, survival, longevity and oviposition period, and delayed development of immature stages (i.e., egg hatch time and larval and pupal durations) in the upcoming generation of M. domestica. The values of population parameters such as intrinsic rate of increase, finite rate of increase, net reproductive rate, age-specific survival rate and fecundity, and age-stage life expectancy and reproductive value, analyzed using the age-stage and two-sex life table theory, were significantly reduced in a concentration-dependent manner in comparison with the control group. In conclusion, the study highlights the significant effects of cyromazine on the biology of M. domestica that could help suppress its population in cases of severe infestations.

The life table parameters of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) reared on nine rainfed barley cultivars

The lesser grain borer, Rhyzopertha dominica (F.) attacks various cereals and causes serious damage during storage periods in many parts of the world including Iran. In this study, the impacts of nine rainfed barley cultivars namely Abidar, Ansar, Izeh, Fardan, Khoram, Mahoor, Nader, Nimroz, and Sararod were determined on the life table parameters of R. dominica in the laboratory, at 25 ± 2 °C, 60 ± 5% RH, and darkness, using the age-stage, two-sex life table theory. The different life table parameters of R. dominica were significantly influenced by tested cultivars. The incubation period of R. dominica was longest on Ansar (7.55 d) and shortest on Izeh (6.53 d). Among tested cultivars, developmental time of R. dominica immature stages was longest on Ansar (47.94 d) and shortest on Fardan (45.43 d). The total female life span for insects reared on Ansar (115.82 d) was significantly longer than other cultivars. The highest and lowest fecundities observed fed on Ansar (148.21 eggs) and Nader (81.78 eggs), respectively. Life expectancy (exj) for all stages of individuals reared on Ansar was highest compared to other cultivars. The intrinsic rate of increase (r) differed among tested cultivars and was significantly lowest on Mahoor (0.052 day−1) in comparison to other cultivars. The cluster analysis results indicated that Sararod, Nader, Nimroz, and Mahoor are relatively resistant cultivars for R. dominica performance and can be used in the integrated pest management program for this pest.

How host plants influence the life history and population growth of Myzus persicae (Hemiptera: Aphididae) and its parasitoid, Aphidius platensis (Hymenoptera: Braconidae)

ABSTRACT The effect of three host plants, sweet pepper, cucumber and eggplant, on the survival and fecundity of Myzus persicae (Sulzer) (Hem.: Aphididae) and population growth parameters of Aphidius platensis as a solitary endoparasitoid of green peach aphid were studied. The raw data were analysed using the age-stage, two-sex life table theory. The results showed that sweet pepper is the most suitable host plant for green peach aphid development and reproduction. The intrinsic rates of increase (r) of M. persicae reared on eggplant, sweet pepper and cucumber were 0.32 ± 0.01, 0.33 ± 0.01 and – 0.071 ± 0.06 d− 1, respectively. Furthermore, other population parameters of aphids raised on sweet pepper and eggplant were significantly higher than corresponding parameter values of aphids fed on cucumber plant. The intrinsic rate of increase (r) of A. platensis reared on sweet pepper was 0.29 ± 0.01 d− 1. The life expectancy (exj ) of A. platensis parasitised pepper raised green peach aphids was 21.08 days on the first day of emergence, and the maximum reproductive value of A. platensis females occurred on the 14th day. Our results showed that sweet pepper could serve as a suitable host plant for rearing M. persicae as a host for A. platensis within a biological control programme context according to the pre-adult period, survival, adult longevity and fecundity of M. persicae. This information could be useful for mass rearing of A. platensis in insectariums where the faster growth and development of aphids are desirable.

Biological Fitness Cost, Demographic Growth Characteristics, and Resistance Mechanism in Alpha-Cypermethrin-Resistant Musca domestica (Diptera: Muscidae).

Musca domestica L., a pest of animals and humans, has developed resistance to alpha-cypermethrin, a pyrethroid insecticide commonly used to control medically important pests in many countries, including Saudi Arabia. We investigated the mechanism underlying the development of alpha-cypermethrin resistance and life history characteristics of alpha-cypermethrin-susceptible (Alpha-SS) and alpha-cypermethrin-resistant (Alpha-RS) M. domestica using the age-stage, two-sex life table theory, which is crucial for developing a future rational management strategy and minimizing the negative effects of alpha-cypermethrin on the environment. Our results showed that Alpha-RS M. domestica had a 405.93-fold increase in resistance to alpha-cypermethrin relative to Alpha-SS M. domestica. This increase in the resistance toward insecticide was attributed to metabolic enzymes, such as glutathione S-transferases, specific esterases, and cytochrome P450 monooxygenases. Furthermore, Alpha-RS M. domestica exhibited lower relative fitness (0.50), longevity, survival rate, life expectancy, reproductive values, intrinsic rate of increase, net reproductive rate, fecundity, maternity, and finite rate of increase, along with shorter larval, female preadult, and adult durations than Alpha-SS M. domestica, indicating fitness costs associated with most parameters. However, no significant differences were found between the strains in the following parameters: egg, pupa, and male preadult durations; adult preoviposition, total preoviposition, and oviposition periods; female ratio; and total generation time. Additionally, Alpha-RS M. domestica had a markedly lower intrinsic rate of increase, net reproductive rate, and finite rate of increase than Alpha-SS M. domestica. The results of this study suggest that alpha-cypermethrin resistance may lead to dominant fitness costs in M. domestica. Overall, these findings will aid in the development of rational control strategies for M. domestica as well as help to reduce pesticide pollution.

The effects of the abamectin and spirodiclofen mixture on life history and population parameters of Amblyseius swirskii

In this study, three sublethal concentrations (LC5, LC15, and LC25) of Envidor®speed (Abamectin and Spirodiclofen mixture, 24% SC, Bayer co.) on the biological parameters of the predatory mite Amblyseius swirskii Athias-Heneroit (Acari: Phytoseiidae) fed on Tetranychus urticae Koch (Acari: Tetranychidae) was assessed based on the Two-sex life table theory under laboratory conditions (25 ± 1°C, 70 ± 5% RH and 16:8 (L: D) hours). The data were analyzed based on a two-sex life table procedure. Increasing the sublethal concentration did have a significant effect on some life table parameters. The total lifespan of both males and females treated mites had a decreasing trend, for the females, it increased from 22.10 days in LC25 treatment to 42.67 days in control. The oviposition days of the predatory mite had the most differences between the LC15 and LC25 treatments compared to LC5 and control. Based on our results, the total fecundity is also affected by the acaricidal doses, which changed from 19.10 eggs per individual in LC25 to 37.17 eggs per individual in control. The net reproductive rate (R0), as well as the gross reproductive rate (GRR), were all significantly reduced with increasing the acaricide concentration. The control treatment had the maximum value, and the higher concentration treatment (LC25) had the slowest value of R0 and GRR. On the contrary, the intrinsic rate of increase (r) and finite rate of increase (λ) showed no significant differences with the increasing concentration of acaricide from the control to LC25 treatments. Eventually, with due attention to the large range value of each LCs for predatory mites concerning recommended concentration for T. urticae based on the active ingredient, the recommended concentration of Envidorspeed in IPM programs is unobstructed.

Temperature-Dependent Biology and Population Performances of the Coffee Berry Borer Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae) on Artificial Diet

At different observation intervals of 1, 5, and 10 days during a trial period of 30 days, the mortality rates of Hypothenemus hampei were 100, 95, and 55%, and the fecundity rates were 0.55, 8.45, and 19.35 eggs/female, respectively. At temperatures of 18, 21, 24, and 27 °C, the development time of the immature stage of H. hampei was significantly shortened with increasing temperature. Furthermore, the lower developmental threshold (T0) and thermal summation (K) of the immature stage were 8.91 °C and 485.44 degree-days, respectively. The greatest longevity of female and male adults reached 115.77 and 26.50 days, respectively, at 18 °C. The highest fecundity was 29.00 eggs/female at 24 °C. The population parameters of H. hampei were analyzed on the basis of the age–stage, two-sex life table theory. According to the data, the parameters were significantly affected by temperature. The highest net reproductive rate (R0) was 13.32 eggs/individual at 24 °C. The highest intrinsic rate of increase (r) and finite rate of increase (λ) were calculated as 0.0401 and 1.0409 day−1, respectively, at a temperature of 27 °C. The shortest mean generation time (T) was 51.34 days at 27 °C. Overall, we provide a discussion on comprehensive biological information regarding H. hampei, thus providing basic knowledge for further research on this pest.

Asymmetric sex body size and reproductive fitness relation and offspring population parameters of Habrobracon hebetor (Say) (Hymenoptera: Braconidae)

Parasitoids show a strong relationship between body size and fitness, but it is unclear whether the relationship is asymmetric or symmetric in males and females of Habrobracon hebetor (Say) (Hymenoptera: Braconidae). This study investigated the effects of male and female body sizes on the reproductive fitness (e.g., longevity and fecundity) of the F0 generation and the population fitness (e.g., survival rate, body size, longevity, and fecundity) of the F1 generation at 28 ± 1 °C, 75 ± 5% relative humidity and 16:8 h light:dark period based on the age-stage two-sex life table theory. The results showed that the body size of F0 generation males and females significantly affected their reproductive fitness, but not the body size of the F1 generation. Larger females had longer lifetimes and oviposition days, and higher reproductive rates than smaller females. Moreover, only small ♀ × small ♂, but not large ♀ × small ♂, small ♀ × large ♂, and large ♀ × large ♂, had a significant impact on the life history parameters, population parameters, paralysis rate, and parasitism rate of the F1 offspring population. Interestingly, the population size, paralysis rate, and variability of the F1 offspring with different body sizes increased to a stable status after 50 days. The study also found that the Weibull function could not fit the survival rate of the parasitoid wasp well. These findings deepen our understanding of the ecology of H. hebetor population and provide important technical parameters for mass-rearing and application of these parasitoid wasps.

Ecophysiological responses of individually and group reared Cydalima perspectalis (Lepidoptera: Crambidae) to alkaloid-containing host plants.

The box tree moth, Cydalima perspectalis (Walker), is an invasive pest of Hyrcanian forests in Iran. In the current study, the effects of two boxwood species, Buxus hyrcana Pojark and B. microphylla Sieb. and Zucc. (Buxales: Buxaceae), were examined on ecophysiology of the pest. The demographic parameters were evaluated based on the age-stage, two-sex life table theory. The physiological characteristics of C. perspectalis were considered through fresh/dry weights and individually/group rearing methods. The results showed that C. perspectalis larvae were able to develop, survive and reproduce on both boxwood species. The developmental times were 41.62 and 41.46 days on B. hyrcana and B. microphylla, respectively. The total lifespan did not differ on boxwood species. However, the difference of fecundity on B. hyrcana (412.82 eggs/female) and B. microphylla (286.06 eggs/female) was significant. The intrinsic rate of increase (r) and finite rate of increase (λ) were significantly higher on B. hyrcana than B. microphylla. The nutritional indices showed that the consumption index (CI) on B. hyrcana were significantly lower than on B. microphylla based on fresh/dry weights in both rearing methods. Conversely, the efficiency of conversion of digested food (ECD) and the efficiency of conversion of ingested food (ECI) on B. hyrcana were significantly higher than on B. microphylla. Despite nonsignificant differences in leaf nutrient contents (except calcium), total protein, triglyceride, and alkaline phosphatase activity were inversely different in larvae compared to adult stage on boxwood species. These findings could help to comprehensively understand the performance of the pest on boxwood species.

Assessment of sublethal and transgenerational effects of spirotetramat, on population growth of cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae).

The cabbage aphid (Brevicoryne brassicae L.) is a devastating pest of cruciferous crops causing economic damage worldwide and notably owing to its increasing resistance to commonly used pesticides. Such resistance prompts the development of integrated pest management (IPM) programs that include novel pesticides being effective against the aphids. Spirotetramat is a novel insecticide used against sap-sucking insect pests, particularly aphids. This study evaluated the toxicity of spirotetramat to adult apterous B. brassicae after 72h using the leaf dipping method. According to the toxicity bioassay results, the LC50 value of spirotetramat to B. brassicae was 1.304mgL-1. However, the sublethal concentrations (LC5 and LC15) and transgenerational effects of this novel insecticide on population growth parameters were estimated using the age-stage, two-sex life table theory method. The sublethal concentrations (LC5; 0.125mgL-1 and LC15; 0.298mgL-1) of spirotetramat reduced the adult longevity and fecundity of the parent generation (F0). These concentrations prolonged the preadult developmental duration while decreasing preadult survival, adult longevity and reproduction of the F1 generation. The adult pre-reproductive period was also extended by spirotetramat treatment groups. Subsequently, the population growth parameters such as the intrinsic rate of increase r, finite rate of increase λ and net reproductive rate R 0 of the F1 generation were decreased in spirotetramat treatment groups whereas, the mean generation time T of the F1 generation was not affected when compared to the control. These results indicated the negative effect of sublethal concentrations of spirotetramat on the performance of B. brassicae by reducing its nymphal survival, extending the duration of some immature stages and suppressing the population growth of B. brassicae. Overall, we demonstrated that spirotetramat is a pesticide showing both sublethal activities, and transgenerational effects on cabbage aphid; it may be useful for implementation in IPM programs against this aphid pest.

Function of yeast extract in greater wax moth farming: does yeast extract always improve the development and reproduction of insects?

TheGalleria mellonella L. (Lepidoptera: Pyralidae) has great nutritional potential for humans and animals and is currently used as a model organism in many biological studies, despite its damage to the apicultural industry and wild honeybee colonies. Yeast extract that promotes insect development and reproduction by containing many necessary nutrients has always been an important yet expensive ingredient in the majority of artificial diets forG. mellonella. To better understand the influence of yeast extract content onG. mellonella mass-rearing, the life table parameters fromG. mellonella mass-reared on increasing amounts of yeast (0% in control, 2, 4, 6, 7, and 9% of the total diet, respectively) under laboratory conditions were analysed according to age-stage, two-sex life table theory. Harvest rate and recruitment cost to produce 10,000 pupae were also assessed to help identify an economically sustainable rearing system. The intrinsic rate of increase (r) and finite rate of increase (λ) varied among diets. Highest values found in theG. mellonella population reared on a 9% yeast extract diet did not differ significantly from those of diets consisting of 4, 6, and 7% yeast extract, whereas these parameters were lowest in yeast-free artificial diets. The cheapest daily cost of rearing a population was 3,966.57 CNY (Chinese Yuan), and the heaviest pupal weight for both females and males (398.10±9.26 and 316.00±7.92 mg, respectively) were found with an artificial diet of 4% yeast extract. This study demonstrates that excessive dietary yeast extract is not always beneficial toG. mellonella. The most effective yeast extract percentage inG. mellonella mass-rearing diets is about 4% based on life table parameters, computer projection, and harvesting costs.

Demographic Characteristics and Population Simulation of Newly Invasive Fall Armyworm on Arachis hypogaea (Fabales: Fabaceae) and Dominant Green Manure Plant in Taiwan.

Spodoptera frugiperda (J.E. Smith) is a severe and fast-spreading pest of numerous agro-economic crops, including miscellaneous, vegetables, and green manure crops. Understanding pest ecology represents a core component in integrated pest management decision-making. In Taiwan, peanut (Arachis hypogaea L.) is an important miscellaneous crop, whereas sesbania (Sesbania roxburghii Merr.) is the most frequently used green manure crop. To improve the S. frugiperda management in Taiwan, the demographic characteristics and population simulation of this pest reared on peanut and sesbania leaves were analyzed using the age-stage, two-sex life table theory. The intrinsic rate of increase, finite rate of increase, and net reproductive rate of S. frugiperda were higher when reared on peanut (0.1625 d-1, 1.1764 d-1, 264.9 offspring) than on sesbania (0.0951 d-1, 1.0997 d-1, and 30.3 offspring). Population projection of S. frugiperda on peanut demonstrated that this crop is a more suitable host plant than sesbania. Yet, this suboptimal host still assures an increasing trend of more than 357-fold individuals in 75 d, from the initial cohort of 10 eggs. Our data suggest that green manure plants in fallowing fields may support the pest's survival all year round, and may be responsible for a successful establishment and unexpected outbreaks of this invasive pest on the neighboring crops in Taiwan. Our study thus highlights the importance of assessing the population dynamics and areawide pest management of an invasive polyphagous pest on a noneconomic crop to mitigate the potential risk of reinfestation and thus outbreaks.

Effects of temperature on growth, survival, and reproduction of Conogethes punctiferalis feeding on corn kernels

In order to examine the effects of temperature on the growth, survival, and reproduction of Conogethes punctiferalis (Lepidoptera: Crambidae) feeding on corn kernels, the life table parameters of C. punctiferalis at 21, 24, 27, 30 ℃ were calculated based on the age-stage two-sex life table theory, and then population dynamics of C. punctiferalis was projected based on these parameters. The results showed that the life cycles of the pest could be finished at all the four temperature treatments. The developmental duration of each stage shortened with increasing temperature, and there were significant differences among treatments. The highest fecundity (116.7 eggs per female), preadult survival rate (84.7%), and proportion of female (0.46) were observed at 24 ℃. The intrinsic rates of increase at 24, 27, 30 ℃ were 0.1059, 0.1101, and 0.1045 d-1, respectively. The finite rates of increase were 1.1117, 1.1164, and 1.1102 d-1, respectively. There was no significant difference among the three treatments, but the r and λ values were significantly higher than those at 21 ℃. The net reproductive rates (R0) at 21, 24, 27, 30 ℃ were 17.3, 53.7, 36.9, and 19.8, respectively. R0 at 24 ℃ was the highest. It suggested that survival rates, fecundities and female proportions of C. punctiferalis population were high at 24-27 ℃, which was the suitable temperature range for its growth, survival, and reproduction.

English

Earias vittella (F) is an important insect pest of cotton (Gossypium hirsutum) and okra (Abelmoschus esculentus) in Pakistan. The current study was carried out to explore the effects of sub-lethal concentrations of novaluron on the life table parameters of the pest. Bioassays were performed to assess the sub-lethal concentrations (LC20 and LC50) of the novaluron and its effects on the demographic parameters of the E. vittella. Age-stage, two-sex life table theory was applied to interpret the data for population parameters of E. vitella. In the current study, the LC20 and LC50 were calculated as 2.224 ppm and 9.837 ppm, respectively. The results showed that in novaluron treated samples rates of all biological parameters decreased whereas the larval, pupal period and mean generation time were increased. The intrinsic rate of increase remained high in control as 0.166 d-1 in comparison with LC50 as 0.128 d-1. The net reproductive rate ranged from 94.542 offsprings per individual (control) to 61.228 offsprings per individual (LC50). Fecundity was dropped in insects treated with sub-lethal concentrations from 330.9 eggs per female (control) to 238.11 eggs per female (LC50). This study revealed that the sub-lethal concentrations of novaluron significantly decreased the biological rate of E. vitella under laboratory conditions and suggests that such doses should be practiced in the fields for proper integrated pest management strategies. © 2022 Friends Science Publishers

ZnO nanoparticles produced in the culture supernatant of Bacillus thuringiensis ser. israelensis affect the demographic parameters of Musca domestica using the age-stage, two-sex life table.

Indiscriminate use of broad-spectrum insecticides can have deleterious effects on insects and the environment. The use of nanoparticles synthesized from microbes has recently gained importance as a safe alternative to conventional insecticides. Recently, zinc oxide (ZnO) nanoparticles synthesized using Bacillus thuringiensis have shown insecticidal potential; however, in addition to its acute toxicity, it is necessary to determine possible sublethal effects at the organismal level to understand the toxicity of a new insecticide. Bt-derived enzymes such as nitrate reductase and other biomolecules play a vital role in the reduction of metal ions to metal nanoparticles. Here, we assessed the acute toxicity and sublethal effects of ZnO nanoparticles produced in the culture supernatant of B. thuringiensis ser. israelensis (Bti) as a reducing agent on the biological traits of Musca domestica. Concentration-response larval bioassays using different concentrations of ZnO-Bti-supernatant nanoparticles revealed LC10 , LC20 , LC50 and LC90 values of 4.17, 6.11, 12.73 and 38.90 μg g-1 of larval diet, respectively. Exposure of M. domestica larvae to two concentrations (LC10 and LC20 ) resulted in a lengthened developmental time (egg to adult) and preoviposition period, and reduced fecundity, survival, longevity and oviposition period. Furthermore, population parameters including net reproductive rate, mean generation time, age-specific survival rate, fecundity, life expectancy and reproductive values, analyzed following age-stage and two-sex life table theory, were significantly decreased after exposure to these concentrations of ZnO-Bti-supernatant nanoparticles compared with the control. ZnO-Bti-supernatant nanoparticles were shown to be toxic to M. domestica. Exposure of M. domestica to low concentrations of ZnO-Bti-supernatant nanoparticles resulted in negative transgenerational effects on progeny production in this fly. © 2022 Society of Chemical Industry.

Sublethal and transgenerational effects of afidopyropen on biological traits of the green peach aphid Myzus persicae (Sluzer)

The green peach aphid, Myzus persicae (Sulzer), is a cosmopolitan agricultural pest and causes great damages each year. Afidopyropen is a novel insecticide with high efficacy against even the insecticides resistant M. persicae. However, the sublethal and transgenerational effects of afidopyropen on M. persicae is not clear. In the present paper, sublethal and transgenerational effects of afidopyropen on biological traits of M. persicae were determined based on the age-stage, two-sex life table theory. The afidopyropen was more toxic against M. persicae than other widely used insecticides, with LC50 of 0.086 mg/L. The treatment with LC5, LC15 and LC25 concentrations of afidopyropen remarkably reduced the longevity and fecundity of F0M. persicae by 15.9–64.4% and 24.3–76.7%, respectively, compared with those of the control. The life history traits of F1 generation including the pre-adult development time, mean total longevity, pre-adult survival rate, total pre-oviposition period and fecundity were significantly affected after treatment of the F0 with afidopyropen, and the population parameters, including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) were also remarkably decreased, while the mean generation time (T) was extended by 6.94%. Among four development and reproduction related genes investigated, JHEH was downregulated by 31.8–38.0% in the afidopyropen treated F0 generation, while the EcR and JHAMT were overexpressed and the Vg was significantly downregulated in F1 generation compared to the control group. All these data indicated that the afidopyropen had significant sublethal and transgenerational effects on M. persicae. These results provide insights into comprehensively understanding of the insecticidal effects of afidopyropen on M. persicae as well as the management of resistant M. persicae.