Lower Developmental Threshold Research Articles

Occurrences of White Prunicola Scale, <i>Pseudaulacaspis prunicola</i>, and Mulberry Scale, <i>Pseudaulacaspis pentagona</i>（Hemiptera: Diaspididae）, in Peaches in Yamanashi Prefecture, Japan, and the Control Effects of Various Insecticides on White Prunicola Scale

In peach cultivation in Yamanashi Prefecture, fruit growers used insecticides to control Pseudaulacaspis prunicola（Maskell）（Hemiptera: Diaspididae）, but serious damage occurred. Therefore, we investigated the dominant species of scale insects on peaches. P. prunicola has a closely related species, P. pentagona（Targioni-Tozetii）, and the occurrence period of P. pentagona larvae of the 1st generation has been observed 9–13 days later than that of P. prunicola. However, the dominant species observed was P. prunicola. We suspected a time lag due to climate change between the occurrence of the 1st generation of P. prunicola larvae and the spraying of insecticides. However, the peak time of larval occurrence calculated from the effective accumulated temperature（144.1 degree-days; lower development threshold temperature 10.0°C; calculated from January 1）matched the timing of spraying. Furthermore, we observed the highly control effects of buprofezin at variously timed applications on P. prunicola larvae collected from Japanese plums cultivated under low pest control pressure. Buprofezin has been used as a principal insecticide for P. prunicola in Yamanashi Prefecture. However, the effect of buprofezin on P. prunicola, collected from five peach orchards cultivated by the practice method, was low. This suggests that low sensitivity to buprofezin is one of the causes of the frequent occurrence of P. prunicola.

Biological traits of the predatory mirid Macrolophus praeclarus, a candidate biocontrol agent for the Neotropical region.

The predatory mirid Macrolophus praeclarus is widely distributed throughout the Americas, and is reported to prey upon several horticultural pest species. However, little is known about its biology, thermal requirements, crop odour preferences, phytophagy, and capability to induce defensive responses in plants. When five temperatures studied (20, 25, 30, 33 and 35°C) were tested and Ephestia kuehniella was used as prey, the developmental time from egg to adult on tomato, was longest at 20°C (56.3 d) and shortest at 33°C (22.7 d). The ability of nymphs to develop to adults decreased as the temperature increased, with the highest number of nymphs reaching the adult stage at 20°C (78.0%) and lowest at 35°C (0%). The lower and upper developmental thresholds were estimated at 11.2° and 35.3°C, respectively. The maximum developmental rate occurred at 31.7°C and the thermal constant was 454.0 ± 8.1 degree days. The highest predation rate of E. kuehniella eggs was obtained at 30°C. In Y-tube olfactory choice tests, M. praeclarus selected tomato, sweet pepper and eggplant odours more frequently than no plant control treatment. Macrolophus praeclarus feeding did not damage tomato plants compared to another zoophytophagous mirid, Nesidiocoris tenuis, which caused necrotic rings. The phytophagy of M. praeclarus induced defensive responses in tomato plants through the upregulation of the jasmonic acid metabolic pathway. The implications of the findings for using M. praeclarus in tomato biological control programmes in the Americas are discussed.

Spatial analysis of changes in Plodia interpunctella (Lepidoptera: Pyralidae) distribution depending on diets

Plodia interpunctella is a globally important insect pest that infests stored food products. Infestation may cause a substantial increase in economic costs for pest control and entails quality loss and dissatisfaction of consumers. The aim of this study was to predict the potential distribution of P. interpunctella feeding on four different diets (rice bran, vegetables, wheat bran, or walnuts) using a CLIMEX model and provide basic data for the storage and management of processed food products. To estimate the CLIMEX parameter of P. interpunctella feeding on rice bran, the developmental rate at different temperatures was tested, resulting in a lower developmental threshold and the degree days of 12.5 °C and 461 DD, respectively. In the spatial analysis, the climatic suitability of P. interpunctella feeding on rice bran was the highest when compared to other diets and particularly higher than that of walnuts in 23.3% of the total area. Our results are expected to provide basic data for the management of P. interpunctella based on species distribution modeling, which, in our study, produced different predicted distribution patterns based on diet and climate.

Impact of Constant and Fluctuating Temperatures on Population Characteristics of Tetranychus pacificus (Acari: Tetranychidae).

To understand the effect of fluctuating temperature on the population characteristics of Tetranychus pacificus, we determined their life tables under constant temperatures between 10 and 35°C and fluctuating temperatures (12 h per day at each of 5°C above and 5°C below the corresponding constant temperature). Tetranychus pacificus eggs did not hatch when held at a constant temperature of 10°C, whereas 77.6% of the T. pacificus eggs reached an adult life stage at fluctuating temperature 10°C ± 5°C. Female preadult development was faster under fluctuating temperatures 12.5, 15, and 20°C than under constant temperatures, whereas it was not significantly different at temperatures ≥ 22.5°C. The lower developmental thresholds (T0) for female preadult development were 10.24 and 5.73°C for the constant and fluctuating temperatures, respectively, while the thermal summations (K) were 215.10 and 265.64 degree days, respectively. The net reproductive rates (R0) at constant temperatures 15 and 35°C were significantly higher than those at the corresponding fluctuating temperatures. However, for 20, 25, and 30°C, the R0 values were not significantly different between constant and fluctuating temperatures. The intrinsic rate of increase (r) and finite rate of increase (λ) at fluctuating temperatures 10, 20, and 30°C were higher compared to the corresponding constant temperature. However, the values of r and λ at constant 25 and 35°C were higher than those at fluctuating temperature. The differential responses of life history between constant and fluctuating temperatures help to understand the population dynamics of T. pacificus under natural conditions.

Temperature impact on the phenology of Nesidiocoris tenuis feeding on Tetranychus urticae: simulation through life cycle modelling

Climatic factors especially temperature has direct impact on the survival of insects. The mirid bug Nesidiocoris tenuis Reuter is an important predator of whiteflies, leafminers, thrips, mites, and various lepidopterans. The impact of temperature on population parameters of N. tenuis was studied by developing model. The rearing temperature had significant impact on the development of N. tenuis. The development time of each nymphal stage decreased with the increase in rearing temperature. The rate of development for each stage increased linearly with the increase in temperature. The optimum temperature, lower and upper developmental thresholds for immature development of the bug varied from 29.9–33.28, 10.1 to 12.25 and 38.82 to 41.1 °C, respectively. The fertility statistics generated for N. tenuis reared on Tetranychus urticae Koch at different temperatures indicate that temperature between 20 and 35 °C is suitable for population growth and multiplication of the bug, whereas, low temperature (15 °C or below) is not suitable for the same. The present study, however, provides useful information on the impact of temperature on the development, survival, reproduction and life-fertility parameters of N. tenuis which could be used for spatial mapping of the distribution and abundance of the bug, and its possible utilization as bio-control agent under expected climate change.

A degree-day model for predicting adult emergence of the citrus gall wasp, Bruchophagus fellis (Hymenoptera: Eurytomidae), in southern Australia

The citrus gall wasp, Bruchophagus fellis, is a serious pest of citrus in southeast Australia and the ability to accurately predict its highly synchronised adult emergence periods is critical for its effective management. We monitored emergence of the citrus gall wasp for six years during 2010–2017 in southern Australia, yielding a total of 22 site-by-year datasets from two citrus production regions and multiple citrus varieties. For each dataset, the proportions of emerged wasps on different monitoring dates were related to the corresponding degree-days using a 2-parameter Weibull function. The two degree-day parameters, the lower development threshold temperature and biofix date, were estimated at 8 °C and August 1 respectively by cross-validation of a series of candidate values using the sum of squared differences between the predicted and observed median emergence dates as the performance indicator. According to the final fitted Weibull function, 5, 50, and 95% emergence occur when 560, 723 and 835 degree-days above 8 °C have accumulated after August 1. The predicted median emergence dates differed from the corresponding observed median emergence dates by an average of 2.8 days across the 22 datasets. The average deviations for 5 and 95% emergence were slightly larger, at five and four days, respectively. Observed degree-days for median emergence did not differ significantly between the two citrus production regions, indicating there is no need for separate degree-day models for different regions. Based on the degree-day model, an interactive, online timing tool has been developed, allowing growers to use local weather station data to predict when the gall wasp is likely to emerge in average, warm, and cool years.

Development and survival of brinjal shoot and fruit borer Leucinodes orbonalis Guenee (Crambidae: Lepidoptera) at constant and alternating temperatures

Brinjal shoot and fruit borer (BSFB) Leucinodes orbonalis Guenee is a key pest of brinjal and a major constraint to its production in the Indian subcontinent. The influence of constant as well as alternating temperatures on the development and survival of the pest is not known. Also, no information is available on the thermal constant, development thresholds, and phenology for the insect. So, the development and survival of Leucinodes orbonalis were studied under laboratory conditions at five constant (15 ± 1, 20 ± 1, 25 ± 1, 30 ± 1 and 35 ± 1 °C) and six alternating temperatures (25:15, 30:15, 35:15, 25:20, 30:20 and 35:20 °C) with 70 ± 5% R.H. and photoperiod of 14:10 (L:D) h. Under the alternating temperature regimes, maximum and minimum temperatures were maintained in a cycle of 14 and 10 h, respectively. Transition from maximum to minimum temperature followed square waveform and was complete within 10 min. The rate of development of the egg, larval, pupal, and adult stages accelerated with increases in the levels of temperature. Survival of BSFB was highest at intermediate temperature levels (25-30 °C), and it started declining outside this range. The favourable range of constant temperature for the development from egg to adult stage was 20 ± 1–35 ± 1 °C, while all six alternating temperatures were conducive for complete development of the pest. The thermal constant (K) and lower developmental threshold (Tmin) determined from a linear regression analysis for the total development period were 435.39–530.66 DD and 5.69–14.63 °C, respectively. The non-linear models did not fit the data obtained from constant temperature studies, as they overestimated the temperature threshold for the pest. In the case of alternating temperatures, Tmin, Topt, and Tmax for the different developmental stages were in the range of 6.87–10.47 °C, 30.3–30.4 °C, and 41.96–42.31 °C, under Briere-1, Briere-2 and Kontodimas models. Our results provide a framework for forecasting the pest incidence in the field, thus helping in modulating management schedules and techniques to target the weak link in the life cycle of the pest.

Effects of Temperature on Development and Survival of Nymphal Lycorma delicatula (Hemiptera: Fulgoridae).

Lycorma delicatula (White), an invasive planthopper originally from Asia, is an emerging pest in North America. It is important to understand its phenology in order to determine its potential range in the United States. Lycorma delicatula nymphs were reared on Ailanthus altissima (Miller) (Sapindales: Simaroubaceae) at each of the following constant temperatures: 5, 10, 15, 20, 25, 30, 35, and 40°C. The time spent in each instar and survival was recorded. Developmental rate increased with temperature from 15 to 30°C for all instars, then declined again at higher temperatures. Nymphal survival was lower at 35°C than between 15 and 30°C for all instars, and first instars placed at 5, 10, and 40°C all died without molting. This suggests that L. delicatula survival and development may be affected in the Southern United States by high temperatures and developmental delays will occur under cool spring conditions. The lower developmental threshold was found to be 13.00 ± 0.42°C for first instars, 12.43 ± 2.09°C for second instars, 8.48 ± 2.99°C for third instars, and 6.29 ± 2.12°C for fourth instars. The degree-day (DD) requirement for nymphs in the previous instar to complete development to reach the second instar, third instar, fourth instar, and adult was 166.61, 208.75, 410.49, and 620.07 DD (base varied), respectively. These results provide key data to support the development of phenology models and help identify the potential range of L. delicatula in North America.

Effects of temperature on life histories of three endangered Japanese diving beetle species

AbstractTo elucidate population‐increasing factors in the diving beetle Cybister tripunctatus lateralis (Fabricius) (Coleoptera: Dytiscidae) in Japan in recent years, life histories and oviposition patterns were compared among three endangered diving beetle species, Cybister brevis Aubé (qualified by the Japanese Red Data List as ‘near threatened’), Cybister chinensis Motschulsky (vulnerable), and C. tripunctatus lateralis (vulnerable). Oviposition in C. brevis, C. chinensis, and C. tripunctatus lateralis was observed from late April to mid‐June, from late April to early July, and from late May to mid‐August, respectively, under semi‐outdoor conditions. There were no interspecies differences in total hatchling production during the reproductive season. In rearing experiments at various temperatures (20, 23, 25, 28, and 30 °C), the mortality of C. tripunctatus lateralis larvae was higher at 20 °C, and gradually lower with increasing temperature up to 30 °C. Adult body size of females in C. tripunctatus lateralis is larger than that of males but there were no significant differences among temperatures (25–30 °C). Cybister brevis had a higher emergence rate at 23–28 °C than at 20 and 30 °C. In C. brevis, the body size of adults reared at 25 or 28 °C was significantly larger than at other temperatures. Cybister chinensis did not differ in emergence rate and adult body size among the five temperature conditions. The developmental zero (i.e., the lower developmental threshold) from the first instar to adult emergence was 11.1 °C for C. brevis, 8.7 °C for C. chinensis, and 16.8 °C for C. tripunctatus lateralis. We speculate how the influence of global warming may have a positive impact on the growth and survival of C. tripunctatus lateralis.

Thermal biology of Tuta absoluta: demographic parameters and facultative diapause

The South American tomato pinworm, Tuta absoluta, (SATP) is now a devastating pest worldwide of crops in the family Solanaceae. Most prior studies of SATP’s thermal biology were based on populations from tropical regions, and proved unsuitable for explaining its invasion of large areas of the Palearctic. A more holistic approach to the analysis of its thermal biology is essential background for developing models to assess its invasive potential. Our studies found that SATP has lower and upper thermal thresholds (θL = 5.37 °C and θU = 35.69 °C, respectively) than South American populations used in prior studies (θL = 7.38 °C and θU = 33.82 °C). Age-specific life tables were used to estimate the effects of temperature on its demographic parameters. Diapause in SATP had not been characterized prior to our study. We found facultative diapause in pupae developing from larvae exposed to relatively low temperatures (i.e., 2 and 5 °C) and short-day length for different exposure periods. The strength of diapause was measured as an increase in post-treatment developmental times of pupae (i.e., degree days) that on average were 2.45–3-fold greater than of pupae reared at favorable temperatures. A lower developmental threshold and a facultative diapause increase the invasive potential of SATP in temperate areas. Knowledge of this thermal biology is essential for predicting the potential geographic spread of this pest and to develop management and control strategies.

Deciphering the effect of climate warming on an emerging poplar pest using spatial extrapolation of population parameters

Abstract The woolly poplar aphid Phloeomyzus passerinii Signoret (Aphididae: Phloeomyzinae) is a major pest of poplar plantations. We hypothesized that recent temperature increases may have contributed to the emergence and subsequent northward expansion of outbreaks in France. We reared P. passerinii at four temperatures to estimate its thermal requirements. We used experimental data to parametrize a mechanistic and temperature‐driven physiologically‐based demographic model. The model was used to simulate the effect of temperature on aphid dynamics and to assess the role of climate warming on the spatiotemporal dynamics of outbreaks. The lower developmental threshold was estimated at 6.4 °C and the development degree‐days at 171. Our model supports the hypothesis that recent warming may have promoted outbreaks in northern France. During recent exceptionally warm years, more than 70% of the northern poplar area was favourable for outbreaks. Our model suggests that climate warming is not the sole factor involved. The dominance of resistant poplar genotypes such as ‘Robusta’ or ‘Beaupré’ may have preserved plantations from outbreaks before 1996 in southern France and until 2000 in the central part. Other factors, including biological characteristics, biotic interactions, or precipitation should be investigated.

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.

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.

Egg Hatching and First Instar Falling Models of Metcalfa pruinosa (Hemiptera: Flatidae).

Since the citrus flatid planthopper, Metcalfa pruinosa (Say), was introduced in Korea and many European countries, it has caused serious damage to various agricultural crops and landscape plants. Metcalfa pruinosa hibernates as eggs beneath the bark and in cracks of tree branches, and then substantial numbers of the first instar nymphs fall from the trees and move to other host plants. Knowing the timing of egg hatching and falling of the first instar nymphs would be key for controlling M. pruinosa. In this study, the hatching of overwintered M. pruinosa eggs and falling of the first instar nymphs from trees were monitored in several areas of Korea. These data were modeled with two starting points for degree-day accumulation, 1 January and 18 March, with a lower development threshold of 10.1 °C. The egg hatching and first instar falling models both used 1 January because the starting point performed better. The 50% appearance and falling times of the first instar nymphs were predicted to be 360.50 DD and 452.23 DD from 1 January, respectively, indicating that newly hatched nymphs stayed on the trees for about a week (i.e., 91.74 DD). Using these models, changes in the population density of the first instar nymphs of M. pruinosa on the trees were simulated, and the optimal control time range targeting the nymphs on the trees was deduced. The control time for nymphs on ground plants bordering the trees was suggested by the first instar falling model, along with observations of population density on the ground plants.

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.

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.

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.