Pre-adult Survival Research Articles

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.

The Effects of Alternative Foods on Life History and Cannibalism of Amblyseius herbicolus (Acari: Phytoseiidae).

The development, survivorship, fecundity, and cannibalism of the predatory phytoseiid mite, Amblyseius herbicolus (Chant), fed six different alternative foods (Oulenziella bakeri, Tyrophagus putrescentiae, Aleuroglyphus ovatus, almond pollen (Prunus armeniaca), apple pollen (Malus pumila), maize pollen (Zea mays)), and natural prey (Tetranychus urticae) were determined in the laboratory. Our findings indicated that A. herbicolus that fed on all six alternative foods could normally complete its developmental and reproductive cycles. The shortest pre-adult developmental duration was observed when A. herbicolus fed on almond pollen (4.91 d) as well as T. urticae (4.90 d), and the longest when it fed on maize pollen (6.24 d). Pre-adult survival rates were higher when the predator fed on almond pollen (0.99), maize pollen (0.96), and O. bakeri (0.93). The highest fecundity was observed when A. herbicolus fed on apple pollen (28.55 eggs/female), almond pollen (26.06 eggs/female), and O. bakeri (26.02 eggs/female) in addition to T. urticae (48.95 eggs/female), and the lowest when it fed on maize pollen (7.84 eggs/female). The highest value of the intrinsic rate of increase (r) was obtained when A. herbicolus fed on O. bakeri (0.202 d-1) in addition to T. urticae (0.210 d-1), followed by almond pollen (0.163 d-1), and the lowest was when it fed on maize pollen (0.064 d-1). Cannibalism of conspecific eggs by adults of A. herbicolus did not occur when O. bakeri and T. urticae were provided. The cannibalism rate of the predatory mite was the lowest when fed on almond pollen, T. putrescentiae, and A. ovatus and the highest on apple pollen. Above all, when fed on O. bakeri and almond pollen, and with no or low cannibalism rate, A. herbicolus had the best development, survivorship, fecundity, and population parameters. Therefore, O. bakeri and almond pollen could be potential alternative foods for mass rearing programs of A. herbicolus or to support its population in the fields.

Demographics and host-kill parameters of Diglyphus horticola Khan against Chromatomyia horticola (Goureau).

The pea leafminer, Chromatomyia horticola (Goureau) (Diptera: Agromyzidae) is a polyphagous and serious pest of peas. In India, this pest is attacked by many parasitoids and among them Diglyphus horticola Khan (Hymenoptera: Eulophidae) is an important one, however, demographics and pest-kill potential of this parasitoid has not been studied so far. This study presents the first report on its demographics and pest-kill potential on C. horticola. The parasitoid showed three modes of host-killing behaviour viz. host-feeding, parasitism and host-stinging. The parasitoid females killed more number of hosts by parasitism than host-feeding or host-stinging. The pre-adult survival, net reproductive rate, intrinsic rate of increase (rm) and finite rate of increase (λ) were higher on the 5-days old host larvae than those reared on the 3-days old larvae. Demographics and pest-kill parameters of D. horticola were also better on 5-days old host larvae than on 3-days old host larvae. Based on the study, D. horticola appeared to be a promising biocontrol agent for the suppression of C. horticola in peas and could be promoted through conservation biological control. Further studies are required to standardize the mass production protocol and release rates to use the parasitoid by augmentation.

Evaluating the Effects of Cu2+ on the Development and Reproduction of Spodoptera litura (Lepidoptera: Noctuidae) Based on the Age-Stage, Two-Sex Life Table.

Copper (Cu2+) is a micronutrient that promotes the development and reproduction of organisms. However, with the rapid expansion of modern industry and agriculture, Cu2+ concentrations are increasing, which might have negative impacts on biological and ecological safety. Spodoptera litura is not only an intermittent outbreak pest but also can be used as a model organism to assess environmental and ecological risks. Therefore, the effects of the life history and population parameters of S. litura fed on artificial diets with different Cu2+ concentrations were analyzed using the age-stage, two-sex life table. Our results showed that not only the preadult survival rate but also the intrinsic rate of increase (r) and the finite rate of increase (λ) were significantly increased under exposure to low Cu2+ concentrations (2, 4, and 8 mg/kg). In addition, the population growth of S. litura was significantly faster, indicating that S. litura can adapt well to low concentrations and is likely to undergo outbreaks of damage. Whereas, in addition to a significant reduction in preadult survival rate, population growth rate, pupal weight, pupal length, adult body weight, and oviposition were also significantly reduced under exposure to high Cu2+ concentration (32 mg/kg). And when the concentration reached 64 mg/kg, the survival rate of adults was extremely low, suggesting a decrease in the adaptation of S. litura. These results can help to understand the population dynamics of S. litura and predict potential ecological risks.

Influence of temperature on the development and reproduction of Habrobracon hebetor (Say), as parasitoid of Opisina arenosella Walker

Opisina arenosella Walker is a coconut leaf-eating caterpillar that invaded the Hainan Province of China in 2013. Habrobracon hebetor Say is an ectoparasitoid used as a control agent of various lepidopteran pests. Laboratory experiments were conducted to determine the effects of constant temperatures (16, 20, 24, 28, and 32 °C) on the parasitism, development, survival, and reproduction of H. hebetor on O. arenosella. The results showed that developmental duration and adult longevity shortened with the increase in temperature. The preadult survival rates were higher at 20 to 32 °C (55 to 72%) than at other temperatures. The parasitism rate and the fecundity increased with the increase in temperature, and reached the highest value at 28 °C (82.03% and 325.17 eggs), then decreased at 32 °C (76.96% and 152.57 eggs). The developmental threshold (T0 ) and effective accumulated temperature (k) for completing a generation of H. hebetor were 13.71 °C and 143.28 degree days, respectively. At 28 °C, net reproductive rate (R0 ) and intrinsic rate of increase (r) were 65.03 and 0.229 d−1, respectively. These results can provide a reference for mass rearing and field release of H. hebetor on O. arenosella.

Oviposition preference, population growth and digestive enzymatic function of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) on six legume grains

The cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is one of the most pernicious pests of stored legume grains in tropical and subtropical areas. Population performance and digestive enzymatic function of C. maculatus can be affected by nutritional quality and antinutritional compounds of legume grains on which it was fed. We reared C. maculatus on six legume grains (cowpea, chickpea, mung bean, soybean, faba bean, and peanut) to investigate the effects of the insect feeding on free-choice oviposition preference, population growth and digestive enzyme activity. The laboratory experiments were conducted at 28 ± 1 °C, relative humidity of 65 ± 5% and 24 h darkness. In a free-choice situation with other legume grains present, females laid the highest number of eggs on cowpea, and avoided laying eggs on peanut. Pre-adult survival of the weevil was the lowest on peanut and highest on mung bean. The developmental period on soybean and faba bean was longer than on mung bean and cowpea. Fecundity (number of eggs laid per female) of C. maculatus on cowpea grains was about 3.7-fold more than on peanut. The intrinsic rate of increase (r) and finite rate of increase (λ) on cowpea, mung bean and chickpea were higher than on soybean, faba bean and peanut. Amylolytic activity of fourth instar larvae fed with peanut, soybean and cowpea was higher than faba bean. Total proteolytic activity of these larvae fed with cowpea was higher than chickpea and mung bean. Our results indicate that cowpea, mung bean and chickpea are the most vulnerable hosts to C. maculatus infestation. The grain coat thickness and phenolic content of tested legumes play an important role in the development and population growth of C. maculatus, and these features could be used to develop effective management of this pest by the production of genetically engineered cultivars.

Evolution of a novel female reproductive strategy in Drosophila melanogaster populations subjected to long-term protein restriction.

Reproductive output is often constrained by availability of macronutrients, especially protein. Long-term protein restriction, therefore, is expected to select for traits maximizing reproduction even under nutritional challenge. We subjected four replicate populations of Drosophila melanogaster to a complete deprivation of yeast supplement, thereby mimicking a protein-restricted ecology. Following 24 generations, compared to their matched controls, females from experimental populations showed increased reproductive output early in life, both in presence and absence of yeast supplement. The observed increase in reproductive output was without associated alterations in egg size, development time, preadult survivorship, body mass at eclosion, and life span of the females. Further, selection was ineffective on lifelong cumulative fecundity. However, females from experiment regime were found to have a significantly faster rate of reproductive senescence following the attainment of the reproductive peak early in life. Therefore, adaptation to yeast deprivation ecology in our study involved a novel reproductive strategy whereby females attained higher reproductive output early in life followed by faster reproductive aging. To the best of our knowledge, this is one of the cleanest demonstrations of optimization of fitness by fine-tuning of reproductive schedule during adaptation to a prolonged nutritional deprivation.

A sublethal concentration of afidopyropen suppresses the population growth of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae)

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is an important insect pest of cotton crops worldwide. The objectives of this study were to determine the acute toxicity of afidopyropen and whether there are any effects of sublethal concentrations of afidopyropen on the biological characteristics of A. gossypii. The results showed that afidopyropen possesses high acute toxicity to adult A. gossypii with a 72 h LC50 value of 1.062 mg L–1. A sublethal concentration (LC10) of afidopyropen significantly decreased adult longevity, fecundity and oviposition days of female adults in both F0 and F1 generations. The total pre-adult survival of F1 progeny was also significantly reduced by 30% at the LC10 of afidopyropen. In addition, the nymph developmental time, pre-adult period, adult pre-reproductive period (APRP), and total pre-reproductive period (TPRP) of the F1 progeny were significantly prolonged compared with the control. Several population parameters, including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) of F1 progeny were significantly decreased by a sublethal afidopyropen concentration exposure. These results indicated that sublethal concentration of afidopyropen can significantly suppress A. gossypii population growth. It would be useful for assessing the overall effects of afidopyropen on A. gossypii.

Evaluation of the Toxicity and Sublethal Effects of Acetamiprid and Dinotefuran on the Predator Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae).

Neonicotinoid insecticides affect the physiology or behavior of insects, posing risks to non-target organisms. In this study, the effects of sublethal doses of two neonicotinoid insecticides, acetamiprid and dinotefuran, against Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae) were determined and compared. The results showed that acetamiprid and dinotefuran at LD10 (8.18 ng a.i. per insect and 9.36 ng a.i. per insect, respectively) and LD30 (16.84 ng a.i. per insect and 15.01 ng a.i. per insect, respectively) significantly prolonged the larval stages and pupal stages (except acetamiprid LD10), compared to control. In addition, acetamiprid and dinotefuran at LD30 significantly prolonged the adult preoviposition period (APOP) and total preoviposition period (TPOP). In contrast, the two insecticides at LD10 and LD30 had no significant effect on the longevity, fecundity, reproductive days, preadult survival rate (%), intrinsic rate of increase (r), net reproductive rate (R0), and finite rate of increase (λ). These results provide a theoretical basis for the rational use of these two insecticides and the utilization and protection of C. pallens.

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.

Cascading effects of pre-adult survival on sexual selection.

Sexual selection influences broad-scale patterns of biodiversity. While a large body of research has investigated the effect of mate competition on sexual selection, less work has examined how pre-adult life history influences sexual selection. We used a mathematical framework to explore the influence of pre-adult survival on sexual selection. Our model suggests that pre-adult male mortality will affect the strength of sexual selection when a fixed number of adult males have an advantageous mate-acquisition trait. When a fixed number of males have an advantageous mate-acquisition trait, sexual selection is expected to increase when pre-adult mortality is relatively low. By contrast, if a fixed proportion (rather than number) of adult males have a mate-acquisition trait, pre-adult male mortality is not expected to affect the strength of sexual selection. Further, if the advantageous mating trait affects pre-adult survival, natural and sexual selection can interact to influence the overall selection on the mating trait. Given that pre-adult mortality is often shaped by natural selection, our results highlight conditions under which natural selection can have cascading effects on sexual selection.

Impact of Rice and Potato Host Plants Is Higher on the Reproduction than Growth of Corn Strain Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae).

Simple SummarySince 2016, the fall armyworm (FAW), an invasive pest native to tropical and subtropical regions of the Americas, has invaded Africa and further spread into Asian countries. FAW is a polyphagous species, although the invaded strain mostly damages corn rather than any other host plants. Studies on the biology of corn strain FAW reared on three different host plants: corn, rice, and potato, using the age-stage, two-sex life table, showed that growth, development, survival, and reproduction rate of the corn strain FAW were differentially affected by rice and potato host plants. The reproduction rate was highly affected than other parameters such as growth, development, survival rates. Our results provide important information for the understanding of the population dynamics of FAW and an appropriate management strategy in the newly FAW-invaded agricultural ecosystems.The fall armyworm (FAW), Spodoptera frugiperda, is an invasive pest species that has recently increased its range in most African and Asian countries, causing significant losses to crop yields, especially corn. To develop effective management strategies, it is particularly important to study the biology of FAW in various crops. Here, we utilized the age-stage, two-sex life table to examine the development, survival, and reproduction rate of the corn strain FAW on three different host plants: corn, rice, and potato. The corn strain FAW successfully completed its life cycle in rice and potato, as well as corn plants. However, the growth, developmental time, survival, and reproduction rate differed among the three host plants. The preadult survival rates in corn, rice, and potato were 92%, 81%, and 77%, respectively. Similarly, mean generation time was significantly shorter in corn (35 days), followed by rice (41 days) and potato (42 days), indicating more generations in corn. Interestingly, the net reproduction rate varied greatly among the three host plants. In corn-fed FAW, the net reproduction rate was 472 offspring per individual, whereas, in rice and potato crops, the rates were only 213 and 86 offspring per individual, respectively. Our results suggest that alternative host plants, such as potato and rice, have more effect on reproduction than the growth of corn strain FAW. These results may be useful in predicting the population dynamics of FAW and understanding the potential damage to crops, thus contributing to an appropriate management strategy in the newly FAW-invaded agricultural ecosystems.

Population Parameters and Growth of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) under Fluctuating Temperature.

Simple SummaryThe bean bug, Riptortus pedestris, is a polyphagous species that is an important pest of soybean fields in Asian countries. In this study, we examined the effects of constant and fluctuating temperatures on the development and reproduction of R. pedestris. The effects of thermal conditions were assessed by constructing age-stage, two-sex life tables from a constant temperature of 24 °C and simulated fluctuating temperatures of 24 ± 4 °C, 24 ± 6 °C, and 24 ± 8 °C. At a constant temperature, a number of R. pedestris life table parameters differed from those under fluctuating temperatures. Although similar pre-adult development periods were recorded under constant and fluctuating temperatures, the periods of female longevity and oviposition periods under fluctuating temperatures were significantly longer than those at a constant temperature. Given that temperature is an important abiotic factor for forecasting the population dynamics of arthropods in nature, determining the effects of fluctuating temperatures will make a valuable contribution to predicting R. pedestris population growth.In this study, we determined the influence of fluctuating temperatures on the development and fecundity of the bean bug Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) by collecting life table data for individuals exposed at a constant temperature (24 °C) and three fluctuating temperatures (24 ± 4 °C, 24 ± 6 °C, and 24 ± 8 °C). The raw life history data were analyzed using an age-stage, two-sex life table to take into account the viable development rate among individuals. Based on these analyses, the population projections enabled us to determine the stage structure and variability of population growth under different temperature treatments. Our results revealed shorter periods of immature development and a higher pre-adult survival rate at 24 ± 6 °C than under the other assessed temperature conditions. Furthermore, significant reductions in female longevity were recorded at 24 °C, whereas the fecundity, net reproductive rate, and intrinsic and finite rates of increase were highest at 24 ± 6 °C. These findings reveal that fluctuating temperatures have a positive influence on the life history traits of R. pedestris and indicate that observations made under constant temperatures may not explain sufficiently enough the temperature dependent biological performances of pests in the field.

Visualising the nutritional performance landscapes for the black soldier fly,Hermetia illucens (Diptera: Stratiomyidae)

The black soldier fly (BSF),Hermetia illucens (Diptera: Stratiomyidae), has become one of the most economically important insects that can be a sustainable replacement for traditional feed for swine, poultry, and aquaculture. Despite its emerging importance, studies examining the nutritional requirement of BSF have been scarce. Here we used nutritional geometry approach to determine the separate and combined effects of dietary protein and carbohydrate content on multiple life-history traits and body composition linked to fitness in BSF. BSF larvae were reared on one of 32 chemically defined diets that varied in protein-to-carbohydrate ratio (P:C=1:16, 1:8, 1:4, 1:2, 1:1, 2:1, 4:1, or 8:1) and in protein plus carbohydrate concentration (P+C=60, 120, 180, or 240 g/l). Females developed more slowly into larger adults than males, but two sexes responded to dietary variation in protein and carbohydrate in a similar manner. The topography of the nutritional performance landscapes mapped for all measured traits differed significantly from one another, with the optimal P:C ratio being 1:1.71 for preadult survivorship, 1:1.56 – 1:1.11 for development time, 1:3.36 – 1:3.16 for body weight at adult emergence, and 1:1.83 – 1:1.40 for growth rate. Significant divergence in nutritional optima among these components of fitness indicates that the occurrence of fundamental life-history trade-off can be mediated by macronutrient intake. The index representing the preadult performance of BSF had a nonlinear relationship with dietary protein, with the peak centred at the intermediate P:C ratios of 1:1.43 – 1:1.37. The optimal P:C ratio was 1:2.12 – 1:1.70 for lean body weight and 1:14.14 – 1:10.82 for lipid content. Our results highlight the importance of the balanced composition of dietary protein and carbohydrate for optimising BSF performance and have implications for enhancing the mass production of this beneficial species.

Host Plant Species Mediates Impact of Neonicotinoid Exposure to Monarch Butterflies.

Simple SummaryNeonicotinoids are the most widely used insecticides in North America and many studies document the negative effects of neonicotinoids on bees. Monarch butterflies are famous for their long-distance migrations, and for their ability to sequester toxins from their milkweed host plants. The neonicotinoids imidacloprid and clothianidin were suggested to correlate with declines in North American monarchs. We examined how monarch development, survival, and flight were affected by exposure to neonicotinoids, and how these effects depend on milkweed host plant species that differ in their cardenolide toxins. Monarch survival and flight were unaffected by low and intermediate neonicotinoid doses. At the highest dose, neonicotinoids negatively affected monarch pupation and survival, for caterpillars that fed on the least toxic milkweed. Monarchs fed milkweed of intermediate toxicity experienced moderate negative effects of high insecticide doses. Monarchs fed the most toxic milkweed species had no negative consequences associated with neonicotinoid treatment. Our work shows that monarchs tolerate low neonicotinoid doses, but experience detrimental effects at higher doses, depending on milkweed species. To our knowledge, this is the first study to show that host plant species potentially reduce the residue of neonicotinoid insecticides on the leaf surface, and this phenomenon warrants further investigation.Neonicotinoids are the most widely used insecticides in North America. Numerous studies document the negative effects of neonicotinoids on bees, and it remains crucial to demonstrate if neonicotinoids affect other non-target insects, such as butterflies. Here we examine how two neonicotinoids (imidacloprid and clothianidin) affect the development, survival, and flight of monarch butterflies, and how these chemicals interact with the monarch’s milkweed host plant. We first fed caterpillars field-relevant low doses (0.075 and 0.225 ng/g) of neonicotinoids applied to milkweed leaves (Asclepias incarnata), and found no significant reductions in larval development rate, pre-adult survival, or adult flight performance. We next fed larvae higher neonicotinoid doses (4–70 ng/g) and reared them on milkweed species known to produce low, moderate, or high levels of secondary toxins (cardenolides). Monarchs exposed to the highest dose of clothianidin (51–70 ng/g) experienced pupal deformity, low survival to eclosion, smaller body size, and weaker adult grip strength. This effect was most evident for monarchs reared on the lowest cardenolide milkweed (A. incarnata), whereas monarchs reared on the high-cardenolide A. curassavica showed no significant reductions in any variable measured. Our results indicate that monarchs are tolerant to low doses of neonicotinoid, and that negative impacts of neonicotinoids depend on host plant type. Plant toxins may confer protective effects or leaf physical properties may affect chemical retention. Although neonicotinoid residues are ubiquitous on milkweeds in agricultural and ornamental settings, commonly encountered doses below 50 ng/g are unlikely to cause substantial declines in monarch survival or migratory performance.

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.

Semi-field demographic performance of the invasive planthopper, Orosanga japonica (Hemiptera: Ricaniidae) on two host plants

Development of Orosanga japonica on two host plants. a: clip-caged adults, b: egg mass, c: emerged nymphs, d: third instar nymph. • Orosanga japonica successfully developed on Rubus ulmifolius and Melia azedarach . • Total immature stage on R. ulmifolius was significantly longer than M. azedarach. • Survival rate was 53.2% and 51.7% on R. ulmifolius and M. azedarach , respectively . • Fecundity on M. azedarach was significantly higher than on R. ulmifolius . • Two host plants had insignificant effects on demographic parameters of O. japonica. Orosanga japonica Melichar (Hemiptera: Ricaniidae) is an invasive polyphagous pest in Iran. The planthopper damaged host plants by sap-sucking and egg laying on new twigs. This study aimed to determine the life table parameters of O. japonica on Rubus ulmifolius Schoot (elm leaf blackberry) and Melia azedarach L. (chinaberry) under field conditions in Rudsar (North of Iran) during 2019–2020. The collected life history data were analyzed based on age-stage, two-sex life table theory. The results showed that the incubation period of O. japonica was too long (≈ 270 days) on both host plants. The nymphs emerged from mid-May 2020. The planthopper had five nymphal stages under field conditions. The nymphal duration was 41.39 ± 0.56 days and 38.13 ± 0.62 days on R. ulmifolius and M. azedarach, respectively. The total preadult survival rates were 53.2% and 51.7% on R. ulmifolius and M. azedarach, respectively. Based on the results, a significant shorter total developmental time was observed on M. azedarach . When adults emerged in late July, they laid eggs after 26.05 days and 26.75 days on R. ulmifolius and M. azedarach, respectively. The fecundity on M. azedarach (131.69 egg/female) was significantly higher than that on R. ulmifolius. However , the life table parameters were all not significantly different on the two host plants. The intrinsic rate of increase ( r ) were 0.0097 ± 0.0005 day −1 and 0.0105 ± 0.0006 day −1 on R. ulmifolius and M. azedarach , respectively. Generally, these findings could be helpful to establish an efficient management strategy for this exotic pest.

Artificial diet significantly enhance fitness and be applicable in mass-rearing of Ephestia elutella (Hübner) (Lepidoptera: Pyralidae)

Ephestia elutella (Lepidoptera: Pyralidae) is a cosmopolitan and polyphagous pest attack a wide variety of stored products. To better understand the effect of an artificial diet and tobacco leaves on mass-rearing performance of E. elutella, the developmental times of preadult and adult stages, total longevity, reproduction, and life table parameters were analyzed from the data gathered from individual and group reared E. elutella under laboratory conditions according to age–stage, two-sex life table theory. The intrinsic rate of increase (r) and finite rate of increase (λ) of group-reared data were found significantly lower than individual-reared data on same rearing medium. Both of these parameters of E. elutella reared on artificial diet were significantly higher than tobacco leaves regardless of whether they were reared individual or group-reared. Moreover, high preadult survival rates and fecundity values were recorded from E. elutella reared on artificial diet. In addition, the mass-rearing system of late instar larvae of E. elutella, which are suitable for mass-rearing an effective parasitoid, Habrobracon hebetor (Say) (Hymenoptera: Braconidae), demonstrate that rearing 10,000 daily E. elutella 5th instar larvae on artificial diet is cheaper than rearing 5th and/or 6th instar larvae on tobacco leaves. Overall, artificial diet used in present study can be used for continuous mass rearing E. elutella.

Demographic modeling to fine-tune conservation targets: importance of pre-adults for the decline of an endangered raptor.

Large, long-lived species with slow life histories and protracted pre-breeding stages are particularly susceptible to declines and extinction, often for unknown causes. Here, we show how demographic modeling of a medium-sized raptor, the Red Kite Milvus milvus, can aid to refocus conservation research and attention on the most likely mechanisms driving its decline. Red Kites' survival and reproduction increased through three sequential stages for 1-2, 3-6, and 7-30yr of age, mainly corresponding to individuals that are dispersing, attempting to gain a territory, and breeding. As typical of long-lived species, elasticities were highest for adult (≥7yr old) survival, but this was high, with little scope for improvement. Instead, the declines were driven by an extremely low survival of pre-adults in their first years of life, which weakened the whole demographic system by nullifying the offspring contribution of adults and curtailing their replacement by recruits. For example, 27 pairs were necessary to generate a single prime age adult. Simulation of management scenarios suggested that the decline could be halted most parsimoniously by increasing pre-adult survival to the mean levels recorded for other areas, while only the synergistic, simultaneous improvement of breeding success, adult and pre-adult survival could generate a recovery. We propose three actions to attain such goals through selective supplementary feeding of both breeding and non-breeding individuals, and through mortality improvement by GPS remote-sensing devices employed as surveillance monitoring tools. Our results show how improving demographic models by using real, local vital rates rather than "best guess" vital rates can dramatically improve model realism by refocusing attention on the actual stages and mortality causes in need of manipulation, thus building precious time and resources for conservation management. These results also highlight the frequent key role of pre-adult survival for the management of long-lived species, coherent with the idea of demographic systems as integrated chains only as strong as their weakest link.

EFFECTS OF CARBOSULFAN ON THE BIOLOGY OF BIRD CHERRY OAT APHID

Aphids are the most commonly occurring, destructive, sap sucking and serious threat to cereal crops especially wheat (Triticum aestivum). Bird Cherry Oat aphid Rhopalosiphum padi (L.), is one of the most important aphids on T. aestivum which is one of the most consumed food and a source of nutrition in Pakistan. It causes considerable yield loss in wheat. Carbosulfan, a carbamate, is of the most commonly used pesticide against R. padi. The effects of Carbosulfan on generations of R. padi were performed under standard lab conditions by exposing adult aphids to three different concentrations (1.4×10-7 ppm, 1.4×10-10 ppm, 1.4×10-13 ppm) of Carbosulfan (Advantage® EC). Based on the results, all three concentrations noticeably reduced the pre-adult survival rate. 1.4×10-13 significantly extended the development duration of 1st instar, 2nd instar and 3rd instar nymphs. 1.4×10-13 ppm also extended the total pre-adult period and female longevity of R. padi. The total longevity was increased by 1.4×10-10 ppm. However, the fecundity decreased the most at 1.4×10-10 ppm. While the TPRP and APRP increased the most at 1.4×10-13 ppm. In the life table parameters, both the intrinsic rate of increase (r) and the finite rate of increase (ƛ) decreased at 1.4×10-7 ppm and 1.4×10-10 ppm, as well as the net reproductive rate (R0) also decreased at 1.4×10-7 ppm and 1.4×10-10 ppm, while mean generation time (T) showed increase at 1.4×10-13 ppm. Thus, at the concentrations of Carbosulfan tested here, there were negative impacts on R. padi fitness and biology by decreased pre-adult survival rate, λ, r, and R0. The concentrations also slowed down the development of some stages and extended T. My results would be helpful in assessing the overall effects of Carbosulfan on R. padi and should be taken into consideration when use Carbosulfan as a seed dressing insecticide for management of R. padi in wheat crop.