Effects of photoperiod and temperature on the developmental duration and diapause in Dolycoris baccarum (Heteroptera: Pentatomidae) from Hohhot, Inner Mongolia, China

The shield bug, Dolycoris baccarum (L.) (Heteroptera: Pentatomidae), is widely distributed across Asia and Europe. At high latitudes, it overwinters, as adult in diapause, which then becomes the insect source for the following year. To fully understand the developmental duration and diapause characteristics of D. baccarum, the effects of photoperiod and temperature were studied in a population from Hohhot, Inner Mongolia, China. The results indicated that the developmental duration was significantly prolonged at temperatures of 20 or 25 °C, with a prolonged light period; however, when the light period was prolonged to 16L:8D and 18L:6D, the developmental duration was shortened significantly. Furthermore, the developmental duration was also shortened significantly with increasing temperature, when the photoperiod was 12L:12D for short days and 16L:8D for long days. All individuals entered diapause under short-day conditions of 10L:14D and 12L:12D at a temperature of 20 °C; however, the diapause rate decreased significantly under 14L:10D and 16L:8D photoperiods, and the diapause rate decreased significantly at a temperature of 25 °C with prolonged photoperiod. Interestingly, when the photoperiod was fixed at 12L:12D, the diapause rates at different temperatures (20, 25, 28, and 30 °C) exceeded 95%; while the effect of temperature on diapauses was nonsignificant under this photoperiod, it was still sensitive to the photoperiod; at a photoperiod of 16L:8D, the effect of temperature on the diapause rate was noticeable, and the diapause rate decreased significantly with increasing temperature.

Influence of Temperature, Photoperiod, and Supplementary Nutrition on the Development and Reproduction of Scutellista caerulea Fonscolombe (Hymenoptera: Pteromalidae)

Scutellista ciruela Fonscolombe has a significant controlling effect on the rubber tree pest, Parasaissetia nigra Nietner. To identify the optimal conditions for the population growth of S. caerulea, we assessed how temperature, photoperiod, and supplementary nutrition affected its development and reproduction. The results demonstrated that the number of eggs laid and parasitism rates of S. caerulea were the highest at 33 °C. The developmental rate of S. caerulea was the fastest and the number of emerged adults the highest. The number of eggs laid and the parasitism rates increased when the light duration increased within a day. Females did not lay any eggs when the whole day was dark. At a photoperiod of 14:10 (L:D), the developmental duration was the shortest and the number of emerged adults was the highest. Adult life span was the longest under a 12:12 (L:D) photoperiod. During the adult stage, supplementary nutrition, such as sucrose, fructose, honey, and glucose, increased the life span of S. caerulea. The life span of S. caerulea was longer when provided with a supplementary diet of sucrose or honey, compared to other tested diets. The results suggested that the most suitable conditions for S. caerulea's population growth were the following: 30 to 33 °C, with 12 to 14 h of daylight, and the provision of sucrose or honey as supplemental diet for the adults.

Threonyl-tRNA synthetase gene, a potential target for RNAi-based control of three rice planthoppers

BACKGROUND

RNA interference (RNAi) has potential as a new strategy for pest control. However, the current overemphasis on the control of a single pest increased control costs. The aim of this study was to find a green method of controlling several pests without affecting the natural enemies with a single target gene. One possible RNAi target is the threonyl-tRNA synthetase (ThrRS), which is conserved and plays a significant role in protein biosynthesis.

RESULTS

In this study, one threonyl-tRNA synthetase gene (NlthrS) was identified from the brown planthopper (Nilaparvata lugens). Spatio-temporal expression pattern analysis showed that NlthrS was highly expressed in the ovary, late embryogenesis, nymphs and female adults. In addition, RNAi-mediated knockdown of NlthrS caused 85.6% nymph mortality, 100% female infertility, molting disorder, extended nymph duration and shortened adult longevity. Target-specific results were obtained when dsNlthrS was used to interfere with the whiteback planthopper (Sogatella furcifera), small brown planthopper (Laodelphax striatellus), zig-zag winged leafhopper (Inazuma dorsalis) and their natural enemy (green mirid bug, Cyrtorhinus lividipennis). In addition, dsNlthrS could cause high mortalities of three species of planthoppers (85.6-100%), while only dsNlthrS-1 led to the death (97.3%) of I. dorsalis that was not affected by dsNlthrS-2. Furthermore, neither dsNlthrS-1 nor dsNlthrS-2 could influence the survival of C. lividipennis.

CONCLUSION

The results reveal the biological functions of ThrRS in N. lugens in addtion to its protein synthesis, deepening our understanding of tRNA synthase in insects and providing a new method for the control of several rice pests via one dsRNA design. © 2022 Society of Chemical Industry.

[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.

Impact of Hypnotic Drug Zolpidem Tartrate on the Development of Forensic Fly Sarcophaga ruficornis (Diptera: Sarcophagidae)

The flesh fly Sarcophaga ruficornis (Fabricius) is one of the fly species of significant medical and forensic importance since it is one of the most common flesh flies used in forensic investigations. Zolpidem tartrate is a sedative-hypnotic drug used for the short-term treatment of insomnia in adults and its use has been implicated in many suicide cases worldwide. Fresh chopped liver of buffalo Bubalus bubalis (Artiodactyla: Bovidae) containing different concentrations of Zolpidem tartrate was given to S. ruficornis larvae to evaluate the effect of Zolpidem tartrate on the developmental rate of the different stages, life cycle duration, and the morphological parameters. The findings have shown significant variation in the time required for the different developmental stages and total life cycle duration, which correlated positively with the Zolpidem tartrate concentration in different cultures. Compared to the control, the morphological parameters were negatively correlated with the concentration of Zolpidem tartrate in the treated cultures. The obtained results indicate that the Zolpidem tartrate retards larval development and alters the estimation of the total developmental duration. Thus, when Zolpidem tartrate may be the cause of death, the entomological evidence needs to be analyzed so it takes zolpidem-related changes to the mPMI into account.

Influence of temperature on the development and reproduction of Cinara cedri (Hemiptera: Aphidoidea: Lachninae)

Temperature is one of the main factors affecting insect growth, development and reproduction. The effects of temperatures (10, 15, 20, 25 and 30°C) on the development and reproduction of Cinara cedri Mimeur (Hemiptera: Aphidoidea: Lachnidae) fed on Cedrus deodara (Roxb.) G. Don were evaluated in this study. With the increase of temperature from 10 to 30°C, the development duration at different development stages gradually shortened. There was a significant positive correlation between the developmental rates and temperature, following a quadratic regression model. The lower developmental threshold temperature (C) and effective accumulated temperatures (K) for completing a generation were 4.13°C and 263.4 degree-days, respectively. The highest fecundity was observed at 20°C with 25.74 first-instar nymphs/female. Both the highest intrinsic rate of increase (r, 0.11 ± 0.03) and net reproduction rate (R0, 19.06 ± 2.05) were observed at 20°C, whereas the lowest values of r (0.05 ± 0.01) at 10°C and R0 (5.78 ± 0.88) at 30°C were observed. The results suggest that temperature significantly affects the biology of C. cedri and the optimal temperature for its development is 20°C.

Duration of Low Temperature Exposure Affects Egg Hatching of the Colorado Potato Beetle and Emergence of Overwintering Adults

Simple Summary

The Colorado potato beetle is a pest of Solanaceae in China, more than 30 species of Solanaceae as host plants of the Colorado potato beetle, and this beetle can cause yield losses to potato farms. Temperature is one of the main factors that affect the growth and survival of insects. In recent years, due to global climate change, sudden drops in short-term temperatures are also frequent, which will affect insects. This paper studies the influence of short-term low temperature on the Colorado potato beetle. In laboratory experiments, we evaluated the effect of short-term low temperature on the Colorado potato beetle eggs, and the emerged date, the number of Colorado potato beetles, were analyzed in combination with the low temperature conditions. Our results show that low temperature had adverse effects on the development of Colorado potato beetle eggs and the emerged of adults Colorado potato beetles, and the longer the low temperature treatment time, the greater the impact.

Abstract

The Colorado potato beetle is a serious pest of Solanaceae in China. In early summer, cold spells in later spring may occur for brief periods in the field environmental conditions, and temperatures often deviate far below the normal temperature for short periods, such as sudden short-term low temperature, may affect the development of Colorado potato beetle eggs. This paper studies the effects of low temperature stress at 8 °C for 0 d, 1 d, 3 d, 5 d, 7 d, and 10 d on the development of Colorado potato beetle eggs. Our results show that egg survival is significantly affected by short-term low temperature exposure. The percentage of eggs hatched is significantly affected by different treatment times (p = 0.000)—the percentage of eggs hatched decreases with increased treatment time, and Colorado potato beetles will extend the wintering time of their soil to resist the effects of lower temperatures. Thus, exposure of Colorado potato beetles to a short-term low temperature affects their emergence and population growth; this study could provide information for the occurrence, monitoring, and early warning of Colorado potato beetle during short-term temperature.

[Effects of four aphid species on development and reproduction of Harmonia axyridis]

To examine the suitability of Myzus persicae, Lipaphis erysimi, Semiaphis heraclei and Aphis gossypii to propagation of Harmonia axyridis population, we studied the development and reproduction of this ladybird by constructing two-sex life table in the laboratory with those four aphid species as diet. The results showed that the immature duration of H. axyridis decreased in an order of L. erysimi (18.18 d), A. gossypii (17.48 d), S. heraclei (16.23 d), and M. persicae (15.77 d). The survival rates of preadult period were S. heraclei (88.3%), M. persicae (86.7%), L. ery-simi (55.0%), and A. gossypii (55.0%). The fecundity of those species were S. heraclei (1750.5), M. persicae (1441.5), A. gossypii (1006.3), and L. erysimi (965.2). The longevity of adult ladybird were S. heraclei (78.8 d), M. persicae (63.1 d), A. gossypii (54.3 d), and L. erysimi (48.4 d). The intrinsic rate of increase (r_m) of H. axyridis population decreased in an order of M. persicae (0.19), S. heraclei (0.18), L. erysimi (0.14), and A. gossypii (0.14). The net reproduction rates (R₀) were S. heraclei (895.83), M. persicae (600.62), L. erysimi (273.47), and A. gossypii (268.33). Among those four aphid species, S. heraclei and M. persicae were more suitable for the propagation of H. axyridis population.

Developmental duration and predation rate of the coccidophagous coccinellid Rhyzobius lophanthae (Blaisdell) (Coleoptera: Coccinellidae) on Aspidiotus nerii Bouche

The consumption rate, survival, and developmental duration of the coccidophagous coccinellid Rhyzobius lophanthae (Blaisdell) (Coleoptera: Coccinellidae), a predator of the armored scale insect, Aspidiotus nerii Bouche (Hemiptera: Diaspididae) were studied under laboratory conditions at two temperature regimes of 25 ± 1 and 30 ± 1°C, 50-65% RH, and 16L:8D. Developmental time (egg to adult) significantly decreased with increase in the temperature. It lasted 27.5 days at 25 ± 1°C and 21.3 days at 30 ± 1°C. The development threshold of R. lophanthae immature stages was 7.823°C, while the thermal constant was 472.379 degree-days. No mortality was recorded during the incubation period. The total mortality rate amongst the larval instars was with 3.33% at 25 ± 1°C and 6.77% at 30 ± 1°C. The sex ratio male to female was 1:1.06. The consumption rate significantly increased with increasing temperatures and within the larval instars. The four larval instar consumed 24.3 and 33.5 adults of A. nerii at 25 ± 1 and 30 ± 1°C, respectively. Overall, micro-climate temperature had a significant impact on the biological parameters of R. lophanthae.

Impact of Constant Versus Fluctuating Temperatures on the Development and Life History Parameters of Aldrichina grahami (Diptera: Calliphoridae)

Necrophagous fly species are commonly used as forensic tools to estimate the minimum postmortem interval (PMI_min). Many researchers raised necrophagous flies under constant temperature regimes to collect their developmental data. However, in most forensic cases, the ambient temperature fluctuates. In order to investigate a forensically important fly developmental mode (the Isomegalen diagram, Isomorphen diagram and Thermal summation models) and make comparisons of the developmental rate between constant temperatures and fluctuating temperatures, we used Aldrichina grahami (Diptera: Calliphoridae) to investigate the life history parameters at eight constant temperatures ranging from 8 to 36 °C. We also compared developmental rate of A. grahami in three groups of constant versus fluctuating temperatures: 8 °C vs. 6–12 °C, 12 °C vs. 10–16 °C, and 16 °C vs. 14–20 °C. Our data showed that A. grahami is cold tolerant with a mean (±SE) development threshold temperature (D₀) of 3.41 ± 0.48 °C and a thermal summation constant (K) of 8125.2 ± 288.4-degree hours. The three groups subjected to fluctuating temperatures took longer to develop compared to those developing in constant temperatures when simulated in a model. These results not only provide detailed developmental data for the use of A. grahami in the estimation of the PMI, but also indicate that ambient temperature fluctuation must be taken into consideration for the use of all necrophagous fly species.

[Effects of pomegranate varieties on the development and fecundity of Assara inouei Yamanaka (Lepidoptera: Pyralidae)]

Assara inouei Yanmanaka is an important pest of pomegranate fruits in Yunnan Province. To examine the effects of different pomegranate varieties on the development and reproduction of A. inouei, the biological characteristics, such as the developmental duration, the survival rate and reproduction of this pest feeding on five pomegranate varieties including Tianlvzi, Houpitianshazi, Tianguangyan, Suanlvzi and Suanshazi were observed respectively, and the life table parameters were established under the laboratory conditions of (25±1) ℃, RH (70±10)% and a photoperiod of 15 L:9 D. The results showed that there were no significant differences in the egg stage, larval stage, pupal stage, the longevity of male adults, generation duration form egg to adult and egg hatch rate among the five varieties. There were significant differences in the pre-pupal stage, the longevity of female adults, larval survival, pupation, eclosion and total survival rates, the number of eggs laid per female as well as male and female pupal mass among the five varieties, and all of which except the larval survival were higher on Suanlvzi, followed by Houpitianshazi, but there was no significant difference between these two varieties. The results of life table showed the net reproduction rate, the intrinsic rate of increase and finite rate of increase of the Suanlvzi population were the highest. There were no significant differences in the mean generation time among the five varieties, but significant difference was observed in the population doubling time, which was the shortest on Suanlvzi population. The development and reproduction of A. inouei were better on the Suanlvzi and Houpitianshazi among the five varieties.

[Sublethal effects of spinetoram and azadirachtin on development and reproduction of Frankliniella occidentalis (Pergande).]

To evaluate the sublethal effects of spinetoram and azadirachtin on western flower thrips, Frankliniella occidentalis, leaf dipping method was used to determine their sublethal concentrations (LC₂₅) on the 2^nd instar nymph, and their influences on development and reproduction of F. occidentalis were studied. The results showed exposure of sublethal concentrations of spinetoram and azadirachtin to F. accidentalis had different degrees of effects on this insect pest. Under bisexual reproduction, the LC₂₅ spinetoram had no significant influences on pre-oviposition period, female adult longevity and fecundity, but male adult longevity was significantly shorter than the control. The LC₂₅ azadirachtin significantly reduced fecundity and prolonged pre-oviposition period. Under parthenogenesis, the LC₂₅ spinetoram and azadirachtin extended the pre-oviposition duration, whereas the LC₂₅ azadirachtin shortened the female adult longevity and significantly decreased fecundity. The LC₂₅ spinetoram and azadirachtin had different influences on developmental duration of each stage of next generation. The immature stage in treatment group of the LC₂₅ spinetoram was shorter than that in treatment group of the LC₂₅ azadirachtin, under bisexual reproduction or parthenogenesis. Intrinsic rate of increase (r_m) and finite rate of increase (λ) of population treated by the LC₂₅ spinetoram were higher than those of the control, whereas the r_m, R₀, and λ of population treated by the LC₂₅ azadirachtin were lower than those of the control. The findings indicated that the effects of the LC₂₅ spinetoram and azadirachtin on the development and reproduction of F. accidentalis were different. The LC₂₅ spinetoram had certain stimulating effect, whereas the LC₂₅ azadirach-tinon had significant inhibitory effect. Two biopesticides' influences were related with the reproductive patterns of F. accidentalis.

Slow and fast development in two aphidophagous ladybirds on scarce and abundant prey supply

Developmental rates are highly variable, both within and between genotypes and populations. But the rationale for two differential (slow and fast) developmental rates within same cohort under varying prey supply has yet not been explored. For this purpose, we investigated the effect of scarce and abundant prey supply on slow and fast development at 27°C in two aphidophagous ladybirds, Menochilus sexmaculatus (Fabricius) and Propylea dissecta (Mulsant) and its effect on their body mass and reproductive attributes. The ladybirds were provided with scarce and abundant supply of Aphis craccivora Koch under standardized abiotic conditions in the laboratory. A clear bimodal (two peaks, where the first peak represented the fast developing individuals and the second peak slow developing individuals) pattern of distribution for both prey supplies was obtained, which got skewed with change in prey supply. On abundant prey supply, more fast developing individuals (139 M. sexmaculatus and 123 P. dissecta) were found and less (46 M. sexmaculatus and 36 P. dissecta) on scarce prey supply. Slow developing individuals had female biased sex ratio, higher longevity and lower body mass. Fast developing females laid higher number of eggs with higher egg viability. Results of the study are indicative of occurrence and constancy of the slow and fast developing individuals in the egg batch.

Diapause induction, color change, and cold tolerance physiology of the diapausing larvae of the Chouioia cunea (Hymenoptera: Eulophidae)

The chalcid wasp Chouioia cunea Yang (Hymenoptera: Eulophidae) is one of the most dominant pupal parasitoids of Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), an invasive pest of many forestry trees and agricultural crops. For mass rearing C. cunea for biological control purposes, the pupae of Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Saturniidae) have been widely used as a substitute host in China. In this article, photoperiodic effect on diapause induction in C. cunea within the pupae of A. pernyi was investigated, and the differences in cold tolerance physiology including supercooling point, water content, and activities of three protective enzymes (Peroxidase [POD], Catalase [CAT], and Superoxide dismuase [SOD]) between diapause and nondiapause mature larvae were comparatively determined. Our results revealed that C. cunea possess a short-day induced larval diapause. The critical photoperiods for diapause induction in C. cunea were estimated to be between a photoperiod of 13:11 and 14:10 (L:D) h at 18°C, or between a photoperiod of 12:12 and 13:11 (L:D) h at 21°C or 24°C. We also found that the color of C. cunea diapausing larvae was taupe, while the normally developed (nondiapausing) individuals were light yellow. This body color change can be used as an indicator of diapause entry of C. cunea larave. The average supercooling point of diapausing mature larvae were lower than those of nondiapausing ones. There were significant differences in the activity of three protective enzymes (POD, CAT, and SOD) between diapausing and nondiapausing mature larvae.

The effects of temperature on the development of the moth Athetis lepigone, and a prediction of field occurrence

Athetis lepigone (Möschler) (Lepidoptera: Noctuidae) is an important insect pest of corn crops in China. To determine the effect of temperature on A. lepigone growth, and to provide a forecasting model for this pest, the development and fecundity of A. lepigone under five different temperatures (18, 21, 24, 27, 30 °C) was investigated, and an experimental population life table was constructed based on the obtained results. The results showed that the duration of development of A. lepigone decreased as the temperature increased from 18 to 30 °C. Approximately 95% of mature larvae stopped pupating at 18 °C, and about 70% of mature larvae stopped pupating at 21 °C. When the growth chamber temperature was above 24 °C, no growth arrest was observed. The results indicated that the optimum growth temperature of A. lepigone was about 26.47 °C. In this study, the highest survival rate, fecundity per female, and population index trend were observed when the temperature was set at 27 °C. The percentages of larvae that could spin cocoons after the 5th or 6th instar differed at the different temperatures. The developmental threshold temperatures for A. lepigone eggs, larvae, pre-pupae, pupae, preoviposition females, and the whole generation (i.e., egg to oviposition) were 11.03, 9.04, 15.08, 11.79, 11.63, and 10.84 °C, respectively, and their effective accumulative temperatures were 63.51, 339.42, 30.04, 118.41, 35.06 and 574.08 degree-days, respectively. Based on the effective accumulative temperature law, this pest insect can have four generations in most of the Huang-Huai region of China, and two to three generations annually in some cold regions. Athetis lepigone may have four generations in the mid-southern part of Hebei Province. This prediction matches the field survey results.

Predatory potential of Chrysoperla carnea and Cryptolaemus montrouzieri larvae on different stages of the mealybug, Phenacoccus solenopsis: a threat to cotton in South Asia

The outbreaks of mealybug, Phenacoccus solenopsis Tinsley (Homoptera: Pseudococcidae), have created problems to cotton crops in South Asia in the recent years. To control this menace, predatory potential of Chrysoperla carnea and Cryptolaemus montrouzieri larvae were investigated under laboratory conditions (27 ± 5° C and 65 ± 5% RH). The experiments were conducted in no choice (only first, second, or third instar larvae of mealybug were offered at a time) and choice (first, second, and third instar larvae were offered simultaneously) feeding tests. Both predators had high consumption rates, with C. montrouzeiri being the most voracious feeder. In the no choice feeding tests, third instar larvae of C. montrouzeiri devoured the highest mean number of first instar P. solenopsis (439.38) In the choice feeding tests, a similar number of first instar nymphs (410) were consumed. In both feeding tests, C. carnea devoured relatively fewer numbers of P. solenopsis than C. montrouzeiri. Manly's preference index suggested that the both predators preferred first instar nymphs of P. solenopsis over second or third instar nymphs. Furthermore, studies on developmental rate and fecundity revealed that first instar nymphs of P. solenopsis significantly reduced development time but increased the fecundity of both predators.

The rearing and biology of the desert beetle, Microdera punctipennis, under laboratory conditions

Microdera punctipennis Kasz (Coleoptera: Tenebrionidae) is a unique species that lives in the desert region of Central Asia and has adopted a nocturnal habit to survive the desert environment. Female adults are larger in size than male adults. The female/male ratio was 1.04:1. A rearing method using reused plastic bottles was used. The rearing conditions were 30 ± 0.5 °C, 30 ± 6% relative humidity (RH), and 16:8 L:D photoperiod. Cabbage was provided as food. Cannibalism was avoided by rearing one larva in a bottle. A complete life cycle was obtained under these conditions. The viability of eggs, larvae, prepupae, pupae, and teneral adults was 93.54%, 83.71%, 84.76%, 87.64%, and 93.59%, respectively. Embryogenesis took 7.35 days on average. The larval duration in each instar was 2.25 days. The mean duration of the larvae, prepupae, pupae, and teneral adult was 49.27, 7.05, 9.95, and 10.12 days, respectively. The coloration of each developmental stage gradually changed from creamy white to light brownish or black. Females commenced oviposition when their body color became black. On average, each female produced 568 eggs.