Developmental Threshold Research Articles

Development of Sarcophaga dux (diptera: Sarcophagidae) at constant temperatures and differential gene expression for age estimation of the pupae.

Sarcophaga dux (Diptera: Sarcophagidae) is a necrophagous flesh fly species with potential forensic value for estimating minimum postmortem interval (PMImin). The basic developmental data and precise age estimates of the pupae are significant for PMImin estimation in forensic investigations. In the present study, we investigated the development data of that species at seven constant temperatures varying from 16°C to 34°C, including body length changes of the larve, developmental duration and accumulated degree hours of the preadults. Several reference genes for relative quantification of the differentially expressed genes (DEGs) were firstly selected and evaluated in the pupae of different ages under different temperatures. The DEGs of the insects during the pupal period at different constant temperatures (34, 25 and 16°C) were further analyzed for more precise age estimation. The results showed that the developmental durations of the preadults at 16, 19, 22, 25, 28, 31 and 34°C were 1478.6±18.3h, 726.1±15.8h, 538.5±0.9h, 394.1±9.5h, 375.6±10.8h, 284.1±7.3h, and 252.5±6.1h, respectively. The developmental threshold temperature the flies was 12.27±0.35°C, and the thermal summation constant was 5341.71±249.29° hours. The most reliable reference genes during the pupal period at different temperatures were found: GST1 and 18S rRNA for the 34°C group, GST1 and RPL49 for 25°C, and 18S rRNA and 28S rRNA for 16°C. The four differential expression genes (Hsp60, A-alpha, ARP, and RPL8) have the potential to be used for more precise age estimation of pupal S. dux. This work provides important basic developmental data and a more precise age estimation method for pupal S. dux, and improves the value of this species for PMImin estimation in forensic investigations.

Effects of Temperature on the Development and Fecundity of Atractomorpha Sinensis (Orthoptera: Pyrgomorphidae)

Over the recent years, Atractomorpha sinensis I. Bolivar, has emerged as an important agricultural pest in China. However, the biological characteristics of A. sinensis remain largely unknown, which can hinder the prediction of its population dynamics. Thus, understanding the impact of temperature on the developmental period of A. sinensis is crucial to predict its population dynamics. The biological characteristics of A. sinensis were systematically observed at five different temperatures (16, 20, 24, 28, and 32°C) using the age-stage, two-sex life table method. The results demonstrated that the developmental period, preadult time, adult longevity, adult preoviposition period, and total preoviposition period were significantly reduced when the temperature was elevated from 16 to 32°C. The developmental threshold temperatures of egg, nymph, preoviposition period, female adult, male adult, and generation were 9.14, 10.44, 12.53, 10.97, 12.47, and 10.58°C, respectively, with the corresponding effective accumulated temperatures of 452.31, 575.99, 169.58, 528.13, 340.81, and 1447.95 degree-days. With an increase in temperature, the intrinsic rate of increase (r) and finite rate of increase (λ) were increased, while the mean generation time (T) was shortened. The optimal values of net reproductive rate (R0= 73.00 offspring) and fecundity (244.55 eggs) were determined at 24°C. Similarly, the population trend index (I) of A. sinensis was found to be highest at 24°C. Our findings indicate that A. sinensis has the greatest rate of population growth at 24°C, which can provide a scientific basis for predicting the in-field population dynamics of A. sinensis.

Development of Hydrotaea spinigera (Diptera: Muscidae) at Constant Temperatures and Its Significance for Estimating Postmortem Interval.

Hydrotaea spinigera Stein is a necrophagous species, widely distributed in Oriental and Australasian regions. Considering that the postfeeding larvae or puparia of this species can still be found in abundance at the advanced decomposition stage or even the skeleton stage of remains, it can serve as a good supplementary indicator for estimating the minimum postmortem interval (PMImin). This could also extend the range of PMImin when the primary colonizers are no longer associated with the corpse or have emerged as adults. This study investigated the development duration, accumulated degree hours, and larval body length changes of H. spinigera at seven constant temperatures ranging from 16 to 34°C, and established three development models for estimating PMImin, including isomorphen diagram, isomegalen diagram, and thermal summation model. At 16, 19, 22, 25, 28, 31, and 34°C, the development durations of H. spinigera from egg to adult stage were 1,412.6 ± 62.9, 867.4 ± 14.9, 657.1 ± 22.9, 532.3 ± 10.1, 418.8 ± 21.3, 379.8 ± 16.6, and 340.0 ± 20.3 h, respectively. The lower developmental threshold L0 was estimated as 10.50 ± 0.20°C, and the thermal summation constant K was 7,648.83 ± 146.74 degree hours. Using regression analysis, equations were obtained modeling the change of larval body length with time after hatching at different temperatures. This study provided basic data based on the growth and development of H. spinigera for the estimation of PMImin in forensic science.

Mind the gap: the delayed recovery of a population of the biological control agent Megamelus scutellaris Berg. (Hemiptera: Delphacidae) on water hyacinth after winter.

Cold winter temperatures significantly affect the biological control effort against water hyacinth, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), in more temperate regions around the world. The population dynamics of the planthopper Megamelus scutellaris Berg. (Hemiptera: Delphacidae), a newly released biological control agent of water hyacinth, were recorded on the Kubusi River in the Eastern Cape Province (South Africa) over 15 months to determine the population recovery post-winter. Megamelus scutellaris incurred a severe population decline at the onset of winter when the water hyacinth plants became frost damaged. The combined effect of a population bottleneck and low minimum winter temperatures (6.12°C) below the agent's lower developmental threshold (11.46°C) caused a post-winter lag in agent density increase. Subsequently, the maximum agent population density was only reached at the end of the following summer growing season which allowed the water hyacinth population to recover in the absence of any significant biological control immediately post-winter. Supplementary releases of agents from mass-reared cultures at the beginning of the growing season (spring) is suggested as a potential method of reducing the lag-period in field populations in colder areas where natural population recovery of agents is slower.

Developmental Biology of Forensically Important Beetle, Necrophila (Calosilpha) brunnicollis (Coleoptera: Silphidae).

The postmortem interval (PMI) estimation, in cases where the body was discovered in an advanced stage of decomposition, is predominantly based on entomological evidence. However, very few forensically important species are sufficiently known in detail to allow a practical application. One of them is the carrion beetle, Necrophila (Calosilpha) brunnicollis (Kraatz, 1877). Its development from egg to adulthood was studied under a range of ecologically relevant constant temperatures to find parameters of thermal summation models. Developmental sexual dimorphism and the presence of developmental rate isomorphy were investigated. Herein we present the lower developmental thresholds and sum of effective temperatures for all developmental stages of N. brunnicollis (egg, first-third larval instar, postfeeding stage, and pupae). We did not find any evidence of developmental sexual dimorphism nor was the presence of developmental rate isomorphy confirmed. Our results present the first thermal summation model of the East Asian carrion beetle that can be used for the PMI estimation.

Estimation of physiological age at emergence based on traits of the forensically useful adult carrion beetle Necrodes littoralis L. (Silphidae)

The main entomological method for post-mortem interval involves estimation of age for immature insects found on a cadaver. Forensic entomologists frequently use the thermal summation value for the total immature development (K), which is a measure of physiological time needed to complete development of a species (age at emergence). K is highly variable within the species. Its true value for an adult insect may be estimated based on insect traits such as size and sex at maturity. Here, we have tested, if size and sex of adult beetles of Necrodes littoralis may be useful for the estimation of the true K. Necrodes littoralis is a Palearctic carrion beetle that frequently colonizes human cadavers in forest and agricultural environments.General and sex-specific thermal summation models for the emergence and models for the relationship between size of adult beetles and their age at emergence were developed for N. littoralis. The models were subsequently tested in the validation study. The general K for N. littoralis was about 469 (+/-25 SE) accumulated degree-days above the developmental threshold of about 8.5 (+/-0.45 SE) °C. Thermal summation parameters of the sex-specific models revealed minor differences compared to the general model. A true K was negatively related to the beetle size. Methods for the estimation of K represented its true value with different accuracy. The highest accuracy was obtained when K was estimated using beetle weight as a predictor variable and the sex-specific models for the relationship between K and size, although sex contributed slightly to this improvement. Using this method the estimated K represented the true K with the error of 6.3%, while the error for K from the general thermal summation model was about 9.7%.In conclusion, the findings demonstrate that physiological age at emergence of N. littoralis may be accurately predicted based on the adult beetle size. Necrodes littoralis is a second beetle species in which the age at maturity was more accurately represented by size-based estimates of K than K from the general thermal summation model. Therefore, we encourage testing the relationship between K and size in all insect species that are used in forensic entomology; particularly blow flies and flesh flies.

Effect of Temperature on the Survival and Developmental Rate of Immature Ooencyrtus mirus (Hymenoptera: Encyrtidae).

Bagrada hilaris (Burmeister) is an invasive pest of cole crops in the southwestern United States. To find potential biocontrol agents of B. hilaris, three egg parasitoids were imported from Pakistan, including Ooencyrtus mirus, a recently described uniparental species. We investigated the effect of temperature on survival and developmental rate in O. mirus from egg to adult. At 14 and 16°C, no adults emerged unless the immatures were transferred later to a warmer temperature. At constant 18°C, a low percentage emerged, but again more emerged if the immatures were transferred to a warmer temperature. Survival ranged from 80 to 96% at 20-37°C and did not differ significantly among these temperatures. No adults emerged at 38°C. Regardless of the amount of time the parasitized eggs were held at 14 and 16°C, the developmental times after returning the eggs to 26°C were similar, suggesting a quiescence process rather than simply slow development. At higher temperatures, the developmental rate increased linearly from 18 to 36°C and then declined at 37°C. The Wang model provided the best fit of the data and estimated a lower developmental threshold at 13.0°C, an optimal temperature at 35.6°C, and an upper developmental threshold of 38.3°C. The thermal constant for total immature development is 168.4 degree-days. The results show 36°C to be the best temperature for rearing O. mirus, and that O. mirus-parasitized eggs can be stored at 14°C for months without losing viability. These are crucial data to consider when mass rearing this biological control agent.

The use of human induced pluripotent stem cells to screen for developmental toxicity potential indicates reduced potential for non-combusted products, when compared to cigarettes

devTOX quickPredict (devTOXqP) is a metabolomics biomarker-based assay that utilises human induced pluripotent stem (iPS) cells to screen for potential early stage embryonic developmental toxicity in vitro. Developmental toxicity potential is assessed based on the assay endpoint of the alteration in the ratio of key unrelated biomarkers, ornithine and cystine (o/c).This work aimed to compare the developmental toxicity potential of tobacco-containing and tobacco-free non-combustible nicotine products to cigarette smoke. Smoke and aerosol from test articles were produced using a Vitrocell VC10 smoke/aerosol exposure system and bubbled into phosphate buffered saline (bPBS). iPS cells were exposed to concentrations of up to 10% bPBS. Assay sensitivity was assessed through a spiking study with a known developmental toxicant, all-trans-retinoic acid (ATRA), in combination with cigarette smoke extract.The bPBS extracts of reference cigarettes (1R6F and 3R4F) and a heated tobacco product (HTP) were predicted to have the potential to induce developmental toxicity, in this screening assay. The bPBS concentration at which these extracts exceeded the developmental toxicity threshold was 0.6% (1R6F), 1.3% (3R4F), and 4.3% (HTP) added to the cell media. Effects from cigarette smoke and HTP aerosol were driven largely by cytotoxicity, with the cell viability and o/c ratio dose–response curves crossing the developmental toxicity thresholds at very similar concentrations of added bPBS. The hybrid product and all the electronic cigarette (e-cigarette) aerosols were not predicted to be potential early developmental toxicants, under the conditions of this screening assay.

Sensitivity analysis, calibration and validation of a phenology model for Pityogenes chalcographus (CHAPY)

The purpose of the study was to develop, calibrate and validate a comprehensive phenological model for the spatiotemporal simulation of the seasonal development of the six-toothed spruce bark beetle, Pityogenes chalcographus (CHAPY). The validation dataset was acquired through monitoring of the bark beetle's phenology at eight sites in Slovenia in 2017 and 2018, along with air and bark temperature measurements. The predictions were made using air temperature from the INCA system (Integrated Nowcasting through Comprehensive Analysis), which is used to calculate the effective bark temperature for beetle development. Since the biology of P. chalcographus is poorly studied, a sensitivity analysis was used to pinpoint the most important model parameters. The first order (main) effect was the highest for the lower developmental threshold (DTL), while the second order (interaction, total) effect was the highest for the optimum temperature (TO). DTL was calibrated with an iterative procedure, and the best result with the lowest mean absolute error (MAE) was achieved at 7.4°C. Effective temperatures in the range between TO and the upper developmental threshold were calculated with a nonlinear function whose parameters were appropriately calibrated. The spring date threshold when the model calculation starts was calibrated with an iterative procedure and set at 9th March, which had the minimum MAE. The onset of Norway spruce infestation in spring was estimated using a lower threshold of 15.6°C for flight activity and a mean thermal sum of 216.5 degree-days (dd) from 9th March onward. The observed mean thermal sum required for total development of filial beetles was 652.8 ± 22.7°C, while the predicted mean thermal sum was 635.4 ± 31.4°C. Re-emergence of parental beetles occurred when 52.7% of the minimum thermal sum for total development was reached. The relative duration of the egg, larval and combination of the pupal and teneral adult developmental stages was 9.4%, 58.2% and 32.4%, respectively. Mass swarming concluded in the end of August when daylength was lower than 13.6 h, which was determined with the independent dataset of 1,017 pheromone traps. The diapause initiation at a daylength < 13.6 h is included in the model as an assumption. Successful hibernation of established broods is predicted by assessing the developmental stage of initiated generations at the 31st December. For validation, we compared the timing of phenological events in the field with predicted events using both 30-minute recorded data at study sites in the field and hourly data from the INCA. The time of spring swarming was estimated with a MAE of 5.6 days. The onset of infestation was predicted with a MAE of 6.0 days. The predicted onset of emergence of filial beetles was estimated with a MAE of 2.1 days. Additionally, CHAPY simulates the number of generations. CHAPY was successfully incorporated into two publicly available web applications. Development of the model revealed several knowledge gaps in P. chalcographus phenology, thus providing opportunities for further research of the second most damaging bark beetle of Norway spruce in Central Europe and for further improvement of the CHAPY model. Potential applications of the model for monitoring and management of P. chalcographus are discussed.

Effects of three constant temperature ranges to control Callosobruchus chinensis (Coleoptera: Bruchidae): a serious pest of pulses in Egypt

The current study was conducted to evaluate the effects of constant temperature (16, 24 and 32 °C) on the biology of Callosobruchus chinensis L. (Coleoptera: Bruchidae). The study revealed that all the biological parameters C. chinensis were affected by the three temperatures tested. The results showed that the duration of egg, larval, pupal and adult longevity were decreased as the temperature increased. The longest duration needed for the insect to complete its life cycle was 76.8 days at 16 °C. Increasing temperature from 16 to 32 °C reduced the period duration needed for the insect to complete its life cycle to 24.7 days at 32 °C. The most favorable temperature for the development of egg, larva and pupa of C. chinensis was 32 °C. The developmental thresholds were 10.62, 7.80, 10.23 and 8.98 °C and the corresponding thermal units were 83.57, 359.45, 137.40 and 579.52 day-degree for egg, larval, pupal and from egg to adult, respectively. Also, analysis of variance showed significant effect of temperature on the pre-oviposition, oviposition and post-oviposition periods. It was clear that survival period of the adult decreased considerably with the increase in temperature from 16 to 32 °C. Also, the data showed that the adult females lived longer than males at all tested temperatures.

Effects of temperature on the development and fecundity of Microplitis similis (Hymenoptera: Braconidae), a parasitoid of Spodoptera litura (Lepidoptera: Noctuidae)

AbstractMicroplitis similis (Hymenoptera: Braconidae) is a solitary endoparasitoid of Spodoptera litura larvae (Lepidoptera: Noctuidae). Here, the effects of constant temperature (18, 21, 24, 27, 30, 33 and 36 °C) on the development and fecundity of M. similis developing in S. litura were studied in the laboratory to clarify the range of its potential distribution and better understand its potential as a biological control agent. The developmental duration of M. similis varied from 10.6 (33 °C) to 27.9 days (18 °C). The developmental threshold temperature and effective accumulative temperature of M. similis were 9.96 °C and 231.14 Degree‐days, respectively. The average adult longevity of M. similis ranged from 5.1 (33 °C) to 26.8 days (18 °C). The maximum fecundity of the parasitoid was observed at 27 and 30 °C, which were 43.07 and 39.73 eggs, respectively. The minimum fecundity of the parasitoid was observed at 18 °C, which was 8.27 eggs. The intrinsic rate of increase (rm) and finite rate of increase (λ) of M. similis were the highest at 30 °C. The net reproduction rate (R0) was the highest at 27 °C and 30 °C, which were 44.34 and 40.39, respectively. We concluded that temperatures in the range 27–30 °C are the most suitable for development and reproduction of M. similis. Our study provides detailed basic information for development and reproduction of M. similis under different temperature conditions.

Age-Stage, Two-Sex Life Table of Chrysodeixis chalcites (Lepidoptera: Noctuidae) at Constant Temperatures on Semi-Synthetic Diet.

The golden twin-spot moth or tomato looper, Chrysodeixis chalcites (Esper), is a polyphagous and worldwide pest that causes important aesthetic damages to banana fruits in the Canary Islands. The life history parameters of C. chalcites were determined under laboratory conditions in base on the age-stage, two-sex life table at 15, 20, 25, 30, and 35°C, 65% relative humidity (RH), and a photoperiod of 16:8 (L:D) h, when it was reared on a semi-synthetic diet. The results show that C. chalcites was able to develop and survive from 15 to 30°C, but no development occurred at 35°C. Developmental threshold temperatures of the egg, larval, pupal, and total preoviposition stages were 10.42, 11.73, 11.22, and 9.42°C, respectively, and their effective accumulated temperatures were 58.31, 265.96, 118.57, and 562.39 degree-days, respectively. The adult longevity was reduced with increasing temperature, which ranged between 16.27 and 34.85 d for females and between 14.27 and 35.21 d for males. The highest values of net reproductive rate (R0) and fecundity were observed at 25°C, with 232.70 offspring and 1,224.74 eggs, respectively. Both the intrinsic rate of increase (r) and finite rate of increase (λ) increased significantly and mean generation time (T) decreased significantly with increasing temperature. These results provide useful information that will allow predicting the impact of climate change on the distribution and population dynamics of C. chalcites and developing successful integrated management programs.

Development, Reproduction, and Life Table Parameters of the Foxglove Aphid, Aulacorthum solani Kaltenbach (Hemiptera: Aphididae), on Soybean at Constant Temperatures

We investigated several characteristics of the development and reproduction of the aphid Aulacorthum solani raised on soybean (Glycine max) at 10 constant temperatures between 2.5 and 30 °C, and described the relationship between temperature and several critical biological characteristics using mathematical models. We found that A. solani could survive and reproduce on soybean at temperatures ranging from 5 to 27.5 °C. High fecundity was observed at temperatures from 12.5 to 20 °C. The lower developmental threshold and thermal constant for this species’ nymphal stages were estimated to be 5.02 °C and 131.2 degree-days, respectively, using a linear model. The upper developmental threshold was estimated to be 33.9 °C using the Lactin-2 model. The optimum temperature for nymphal development was estimated to be 26.9 °C. The maximum total fecundity was estimated as ca. 76.9 nymphs per adult at 18.1 °C. The daily fecundity sharply increased at earlier adult ages, and slowly decreased thereafter until final parthenogenesis occurred, over a range of temperatures from 12.5 to 25 °C. The maximum daily fecundity was estimated to be ca. 6.1 nymphs per adult per day for a 5.2 day old of adult at 21.3 °C using an age- and temperature-dependent model of adult fecundity. In terms of life table statistics, the intrinsic rates of increase and the finite rate of increase were both highest at 25 °C, while the net reproductive rate was highest at 20 °C.

Temperature-dependent development and survival of small hive beetle, Aethina tumida (Coleoptera: Nitidulidae)

The small hive beetle (SHB) Aethina tumida Murray, (Coleoptera: Nitidulidae) is an invasive pest of honey bees recently found in Korea. We investigated the influence of temperature on the development and survival of immature SHBs. The beetle’s immature stages were exposed to different constant temperatures (15, 20, 25, 30, 35, 37 and 39 °C) under stable and continuous dark conditions and a relative humidity of 75 ± 5%. All immature stages successfully developed to the next stage at the temperature range from 15 to 39 °C, except for the egg at 15 °C and wandering larvae and pupae, which suffered 100% mortalities at 39 °C. Total immature developmental period at 18.6 and 35 °C ranged from 53.9 days to 20, respectively. Lower developmental thresholds were determined according to a linear model as 16.0, 11.6, 9.6, 12.6, and 11.8 °C for eggs, feeding larvae, wandering larvae, pupae and total immatures, respectively. Among the non-linear models, Analytis-3/Briere-1 was selected as the best to describe the temperature-dependent developmental rate of all immature stages of SHBs based on Akaike information criterion corrected (AICc) values and biological adequacy. According to this model, optimum and high developmental threshold temperatures for eggs, feeding larvae, wandering larvae, pupae and total immatures were 39.1, 36.5, 33.2, 35.5, and 34.8 °C and 46.5, 44, 40.4, 42.5 and 41.5 °C, respectively. According to the polynomial regression model, maximum survival was estimated at temperatures of 28.2, 28.7, 26.7 and 26.5 °C, of eggs, feeding larvae, wandering larvae and pupae, respectively. This study can be used to predict the potential distribution of SHB in non-native locations.

Thermal requirements of Tuta absoluta (Meyrick) and influence of temperature on its population growth on tomato

The present study deals with the impact of temperature on development, survival, reproduction and population growth of a recently invaded and the most destructive pest of tomato, Tuta absoluta (Meyrick) with the aim to understand its possible expansion in different agro-climatic zones. Though T. absoluta was able to develop between 15° and 35°C, temperature around 25°-30°C was more suitable. Survival and fecundity were highest at 25°C and lowest at 35°C. Developmental threshold for different developmental stages of the pest varied from 6.2 to 9.5°C, while the thermal constant required by the insect to complete the development from egg to adult emergence was 500 degree-days. Population growth parameters were also influenced significantly by the rearing temperature. Intrinsic rate of increase, net reproductive rate and finite rate of increase was higher at 25° and 30°C as compared to other temperature regimes. The study concludes that T. absoluta can be a serious pest of tomato in mid-hills of north-western Himalayan region and the southern plains of India where temperatures varies between 15-35°C. Furthermore, the developmental threshold values indicate that the pest can develop and survive at temperatures as low as 6-9°C without entering the diapause as long as the food is available.

Temperature-dependent development of Omosita colon at constant temperature and its implication for PMImin estimation

Omosita colon (Linnaeus, 1758) (Coleoptera: Nitidulidae) is a species widely distributed in the Holarctic that usually appears during more advanced stages of decay. It is one of the species found on highly decomposed remains. Although O. colon may be a promising indicator of post-mortem interval (PMI) in cases with longer PMI, there is currently no existing research on its growth and development. Therefore, we studied the development of O. colon at seven constant temperatures between 16 and 34 °C and found that O. colon can complete its entire life cycle between 16 and 31 °C, but failed to complete development at 34 °C. At 16, 19, 22, 25, 28, and 31 °C, the developmental duration of O. colon from egg to adult is 95.3 ± 11.4, 62.4 ± 8.5, 45.9 ± 2.8, 34.9 ± 3.4, 30.0 ± 2.6, and 25.2 ± 2.6 d, respectively. Based on the results of development time and accumulated degree days, an isomorphen diagram was plotted and a thermal summation model was established. The mean (±SE) developmental threshold temperature D0 and the thermal summation constant K calculated using the thermal summation model were 10.65 ± 0.16 °C and 514.1 ± 8.7° days, respectively. The results of this study provide fundamental developmental data for the use of O. colon in minimum post-mortem interval (PMImin) estimations.

Temperature-dependent life history of Eutetranychus africanus (Acari: Tetranychidae) on papaya

This study was conducted to further understand the biology of Eutetranychus africanus Tucker, a newly invasive pest mite in Taiwan that can cause serious damage to papaya. We report the life history of E. africanus on papaya in laboratory conditions at 12, 17, 22, 27 and 32 ± 0.5 °C, with 70 ± 5 % relative humidity and a photoperiod of L12: D12. Eggs did not hatch at 12 °C. Both developmental duration and longevity were significantly shortened with the increase of temperature. The longest and shortest developmental durations of the immature stage were 37.28 days at 17 °C and 8.70 days at 32 °C, respectively. The longevity of both sexes varied similarly with the change in temperature, with shorter lifespan in males: Females survived for 3.64 days (shortest) at 32 °C to 17.50 days (longest) at 17 °C, whereas males survived for 11.00 days (longest) at 17 °C to 2.57 days (shortest) at 32 °C. The differences in fecundity were significant among all tested temperatures, with 17.61 eggs/female at 27 °C being the highest. The low developmental threshold and thermal summation of the full immature stage were 11.48 °C and 163.93 degree-days, respectively. In two-sex life table analysis, population parameters were significantly affected by temperature except the net reproduction rate. The highest intrinsic rate of increase was 0.1221 day−1 at 27 °C; the average generation time was the shortest (12.61 days) at 32 °C and the longest (48.70 days) at 17 °C. The highest net reproduction rate was 5.06 eggs/female at 27 °C. This report contributes background knowledge to the management of the damage caused by E. africanuson papaya.This study was conducted to further understand the biology of Eutetranychus africanus Tucker, a newly invasive pest mite in Taiwan that can cause serious damage to papaya. We report the life history of E. africanus on papaya in laboratory conditions at 12, 17, 22, 27 and 32 ± 0.5 °C, with 70 ± 5 % relative humidity and a photoperiod of L12: D12. Eggs did not hatch at 12 °C. Both developmental duration and longevity were significantly shortened with the increase of temperature. The longest and shortest developmental durations of the immature stage were 37.28 days at 17 °C and 8.70 days at 32 °C, respectively. The longevity of both sexes varied similarly with the change in temperature, with shorter lifespan in males: Females survived for 3.64 days (shortest) at 32 °C to 17.50 days (longest) at 17 °C, whereas males survived for 11.00 days (longest) at 17 °C to 2.57 days (shortest) at 32 °C. The differences in fecundity were significant among all tested temperatures, with 17.61 eggs/female at 27 °C being the highest. The low developmental threshold and thermal summation of the full immature stage were 11.48 °C and 163.93 degree-days, respectively. In two-sex life table analysis, population parameters were significantly affected by temperature except the net reproduction rate. The highest intrinsic rate of increase was 0.1221 day−1 at 27 °C; the average generation time was the shortest (12.61 days) at 32 °C and the longest (48.70 days) at 17 °C. The highest net reproduction rate was 5.06 eggs/female at 27 °C. This report contributes background knowledge to the management of the damage caused by E. africanus on papaya.

Validation of degree-day models for predicting the emergence of two fruit flies (Diptera: Tephritidae) in northeast Egypt.

We estimated thermal developmental thresholds (T0 ) and degree-day (DD) constants for the immature stages of two tephritid pests, Bactrocera zonata (Saunders) and Ceratitis capitata (Weidenmann). Males of both species were trapped in an Egyptian guava orchard during the fruiting seasons of 2016 and 2017 and trap catches were compared with peak flights predicted by the DD model based on local weather data. Ceratitis capitata had faster development than B. zonata at 20 and 25 °C, but their overall developmental rate was similar at 30 and 35 °C. The thermal threshold of development (T0 ) of B. zonata was higher than that of C. capitata, indicating greater sensitivity to cold. Although 35 °C yielded the fastest development of both species, survival was higher at 30 °C, with B. zonata experiencing a slight advantage, suggesting better tropical adaptation. Immature development of B. zonata and C. capitata was estimated to require 338 and 373 d, respectively, and 616 and 424 DD for a complete generation. Trap catches over both seasons showed good correspondence to peaks of fly activity predicted by the DD models; deviations from expectation ranged from 0 to 7 d for both fly species. Both species had four overlapping generations per season, with B. zonata abundance peaking in the first generation in both years, but only in 2016 for C. capitata. The models predict about eight and 12 generations per year in northeast Egypt for B. zonata and C. capitata, respectively. These models should be useful for timing pest control measures to coincide with periods of peak fly activity in fruit orchards.

The growth and development characteristics of Spodoptera frugipetda under different temperature conditions

In order to study the main biological characteristics of Spodoptera frugipetda,the developmental duration,fecundity,developmental threshold temperature and effective accumulated temperature of different stages were measured on maize seedlings were used as feed under five temperature conditions:20℃,25℃,28℃,32℃and 35℃,in laboratory.The results showed that the development duration of S.frugipetda(egg,larvae,pupae and adult)was gradually decreased with the increase of temperature within the range from 20℃to 35℃,and the generation development duration was 23.0~48.3 d.The developmental threshold temperatures of egg,larvae,pupa,adult and whole generation were 12.70℃,11.11℃,11.01℃,5.65℃and 9.21℃,respectively.And the effective accumulate temperatures were 39.4 d·℃、201.25 d·℃、134.12 d·℃、171.06 d·℃and 636.53 d·℃.The optimum temperature for eggs,larvae,pupa developing and adults oviposition was 20~32℃.However,the temperature of 15℃and 35℃were not conducive to S.frugiperda growth and development.Base on the tested developmental threshold temperature and effective accumulative temperature,the paper speculated that the generation numbers of S.frugipetda in the middle regions,west,south,southeast,southwest,northeast and northwest were 2.18~8.59,2.28~10.15,3.43~12.13,3.15~8.46,2.75~9.39,1.38~6.87 and 1.11~6.72 respectively in Yunnan Province.

Thermal resilience of Prostephanus truncatus (Horn): Can we derive optimum temperature-time combinations for commodity treatment?

Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is a wood-boring, destructive quarantine insect pest of stored cereal grains and tuber crops. Current disinfestation methods against this pest mainly include fumigants, whose usage in some countries has been contested and discontinued owing to increasing pesticide resistance, public health risks and environmental hazards. Grain temperature treatments thus, offer a sustainable non-chemical and near universally acceptable form of disinfestation for international commodity movement. Currently, blanket temperature treatments are applied regardless of as-yet-unknown P. truncatus developmental stage thermal mortality thresholds that simultaneously optimise grain quality. Here, we used established static and dynamic protocols to determine the low and high thermal profile of P. truncatus larvae and adults measured as critical thermal minima (CTmin), lower lethal temperatures (LLT0), chill coma recovery time (CCRT), supercooling points (SCPs), critical thermal maxima (CTmax), upper lethal temperatures (ULT0) and heat knock-down time (HKDT). We tested the adult ULT-time matrices on maize and sorghum grain quality (germination %) to determine the most effective temperature-time combination(s) retaining optimum grain germination quality. Our results showed adults had higher basal heat (CTmax and HKDT), cold (CTmin, CCRT and SCP) and potential thermal plasticity than larvae (P < 0.05). The LLTs and ULTs ranged −1 to −15 °C and 41–49 °C respectively. Using LLT0 and ULT0, our results showed that for heat treatment, moderate temperature × long duration matrix; i.e. either 45.5 °C × 4 h or 47 °C × 2 h were more efficacious while retaining commodity quality. Similarly, for cold treatment; −9 °C × 4 h, −11 °C × 2 h, −13 °C × 1 h and −15 °C × 0.5 h were effective for complete mortality. These temperature-time combinations may be a sustainable alternative to fumigants in phytosanitary grain disinfestation against P. truncatus or related pests. Such pest- and commodity -specific thermal profiling is critical for development of effective standardised grain disinfestation protocols.