Lower Developmental Threshold Research Articles

Thermal effects on the development, fecundity and life table parameters of Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) on barley

The bird cherry-oat aphid Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) is a polyphagous species with a worldwide distribution. We investigated the development periods of R. padi nymphs, and the longevity and fecundity of apterous females. The study was conducted at six constant temperatures of 10.0, 15.0, 20.0, 25, 30.0, and 32.5°C. R. padi developed successfully from nymph to adult stage at all temperatures tested. The developmental rate of R. padi increased as temperature increased from 10.0 to 25.0°C and declined thereafter. The lower developmental threshold (LDT) and thermal constant (K) of the R. padi nymph stage were estimated by linear regression. Higher and lower temperature thresholds (TH and TL, respectively) were calculated by the Sharpe_Schoolfield_Ikemoto (SSI) model. The LDT and K of the R. padi nymph stage were 5.6°C and 100.6degree-days (DD). The temperature range of the R. padi nymph stage from TL to TH was 26.3°C using the SSI model. Developmental completion of the nymph stages was described using a two-parameter Weibull distribution model. The adult emergence frequency of R. padi over the full range of constant temperatures was simulated using developmental rate functions and the Weibull function. Daily nymph production of R. padi was estimated in relation to adult age and temperature. The biological characteristics of R. padi in relation to temperature were presented by a life table analysis. Life table parameters were estimated with the jackknife method. Biological characteristics of R. padi populations from different geographic areas were discussed.

Temperature-Dependent Biological and Demographic Parameters of Coleomegilla maculata (Coleoptera: Coccinellidae).

Knowledge of the most suitable environmental conditions for an organism growth and development is a prerequisite for developing mass rearing technology. The temperature requirements for development and the optimal range of temperatures for growth and reproduction of Coleomegilla maculata De Geer were studied. The development time of individual C. maculata larvae was determined at 18, 21, 24, 27, 30, 33, and 36 °C. Development times were converted to development rates and fitted to a nonlinear temperature-dependent model and to the linear day-degree model. Life and fertility table analysis was used to determine the optimal temperature for population growth within a range of favorable temperatures including 24, 25, 26, 27, and 28 °C. Nonlinear estimates of thermal maximum (TM) for the postembryonic development of C. maculata was 35.09 ± 10.35 °C. Estimation of TM based on pupal development was much lower at 27.23 ± 1.52 °C. Linear and nonlinear estimates of low temperature development threshold were 13.13 ± and 4.77 ± 3.03 °C for the whole postembryonic development and 10.95 and 9.18 ± 1.36 °C for the pupal stage alone, respectively. The most favorable temperature for population growth was 25 °C, where C. maculata showed significantly higher intrinsic rate of increase (rm = 0.066) and significantly lower doubling time (10.57 d) than the other favorable temperatures tested. A negative value of rm was obtained at 28 °C, indicating population decline occurring at this temperature making it unfavorable for C. maculata.

Temperature-dependent development and oviposition models of Halyomorpha halys (Hemiptera: Pentatomidae)

The brown marmorated stink bug, Halyomorpha halys (Stål), is a polyphagous pest affecting agricultural and forest ecosystems. Despite valuable results from the previous studies, the survival and developmental variation models of the immature development of H. halys and major component models describing reproduction of female adults have not been developed yet. This study was conducted to investigate the stage-specific development and survival of H. halys immatures by combining the results of previous studies and this study. An adult development rate model and three major oviposition component models of H. halys were also developed. Development rates were fitted with a nonlinear Briére model, which estimated optimal temperatures as 32.0 and 30.8°C, lower development thresholds as 10.0 and 13.1°C, and upper development thresholds as 33.6 and 33.5°C for egg and nymph, respectively. In a linear model, the lower development thresholds were 12.5 and 12.8°C for egg and nymph, respectively. Survivorship was the highest at 24.2 and 24.5°C for egg and nymph, respectively. Mean fecundity ranged from 8.3 eggs at 18.8°C to 64.3 eggs at 30.3°C, and was fitted to the Lactin function. Adult survival and the cumulative oviposition rate of H. halys were fitted to a sigmoid function and a two-parameter Weibull function, respectively. Findings in this study provide basic information for the ecology of H. halys, which can be used to optimize environmental conditions for rearing, forecast its phenology and population dynamics in the fields, and predict future distribution of H. halys.

Thermal tolerance of Liothrips tractabilis, a biological control agent of Campuloclinium macrocephalum recently established in South Africa

AbstractThe South American herb Campuloclinium macrocephalum (Less.) DC. (Asteraceae; pompom weed), which invades grasslands, savannas, and wetlands in South Africa, is a recent target for biological control. A foliage‐deforming thrips, Liothrips tractabilis Mound & Pereyra (Thysanoptera: Phlaeothripidae), was released in South Africa in 2013, following confirmation of its host specificity and damage potential in quarantine. However, weed biocontrol agents sometimes fail to establish or have the desired impact because they are poorly suited to the climate of the new range. Thermal tolerance trials, within the range of 15–32.5 °C, were conducted prior to the thrips’ release to determine its developmental threshold and to generate a degree‐day model to highlight areas best suited for its establishment in South Africa. These laboratory data were validated by outdoor trials. The thrips completed development from egg to adulthood at all except the lowest and highest laboratory test temperatures, with developmental duration decreasing with increasing temperature. The lower developmental threshold was estimated at 9.6 °C with 546.9 degree days required to complete development. Within the regions invaded by C. macrocephalum in South Africa, the thrips was predicted to complete 3–9 annual generations. Developmental times in the outdoor trials were largely consistent with those in the laboratory. Liothrips tractabilis is largely compatible with the broader South African climate and seems likely to establish and proliferate on C. macrocephalum populations throughout the country. These predictions have partially been verified in that L. tractabilis has become established at several sites in South Africa, many of these in colder, high‐altitude areas which were predicted to support fewer annual generations.

Temperature-dependent development of the great European spruce bark beetle Dendroctonus micans (Kug.) (Coleoptera: Curculionidae: Scolytinae) and its predator Rhizophagus grandis Gyll. (Coleoptera: Monotomidae: Rhizophaginae)

Dendroctonus micans is an invasive species that has spread throughout Britain, which prompts the question: how is the voltinism of this pest and its biocontrol agent Rhizophagus grandis affected by climate? Dendroctonus micans and R. grandis were reared at a range of constant temperatures. Lower developmental threshold temperature (LDT) and day degree (DD) requirements for the egg, larval and pupal stage of D. micans were estimated to be 7.4 °C 153 DD, 6.6 °C 527 DD and 7.2 °C 126 DD, respectively. At 12.5, 15 and 17.5 °C, prior to prepupal cell formation, fifth-instar larvae underwent a diapause, which has not been observed previously in this species. Prepupal development rate also did not increase linearly with temperature. For R. grandis, the LDT and DD requirements for the egg, larval, prepupal and pupal stages were 5.7 °C 84 DD, 6.2 °C 263 DD, 8.1 °C 90 DD and 6.8 °C 178 DD, respectively. At 12.5 and 15 °C, most prepupae failed to pupate, which is indicative of a facultative diapause. The key developmental parameters reported in the present study may be used to model the phenology of the beetles throughout their range, providing better-timed control strategies or to predict outbreak risk under climate change as a result of reduced biocontrol effectiveness.

Effect of temperature on rate of development, survival and adult longevity of Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), is a major pest of potato, Solanum tuberosum L. (Solanales: Solanaceae), both in the field and storehouses. The rate of development and survival of P. operculella, reared on potato tubers cv. Spunta at eight constant temperatures (17.5, 20, 22.5, 25, 27.5, 30, 32.5 and 35°C), were studied in the laboratory. The duration of development of the immature stages was recorded. Adult longevity was also recorded under the same conditions. Developmental time decreased significantly with increase in temperature within the range 17.5-32.5°C. No development occurred at 35°C. Survival (%) from egg to adult was higher at temperatures within the range 17.5-27.5°C than at either 30 or 32.5°C. Linear and a non-linear (Logan I) models were fitted to our data in order to describe the developmental rate of the immature stages of P. operculella as a function of temperature and estimate the thermal constant (K) and critical temperatures (i.e., lower developmental threshold, optimum temperature for development, upper developmental threshold). Lower developmental threshold and optimum temperature for development ranged between 12.5-16.2 and 31.7-33.8°C, respectively. The estimated upper developmental threshold for total immature development was 35.0°C. Thermal constant for total development was 294.0 degree-days. Adult longevity was significantly shorter at high (30 and 32.5°C) than at low temperatures (17.5-27.5°C). Our results not only provide a broader insight into the thermal biology of P. operculella, but also can be used as an important tool in planning an effective pest control program both in the field and storehouses.

Temperature-dependent development of immature stages of predatory ladybird beetle Stethorus vagans (Coleoptera: Coccinellidae) at constant and fluctuating temperatures

Influence of temperature on the development of the predatory ladybird, Stethorus vagans Blackburn, fed on Tetranychus urticae Koch was assessed at seven constant (10, 12, 15, 20, 25, 30 and 35 °C) and fluctuating (12.7–32.1 °C) temperatures. There was a strong positive correlation (r = 0.99) between rate of development and temperature. The development times from egg to adult emergence were 65.2±2.3 and 9.2±0.3 days at 12 and 30 °C constant, respectively and 15.4±0.3 days at fluctuating temperature. Average egg incubation period decreased from 16.5±0.8 to 2.18±0.2 days with increasing temperatures from 12 to 30 °C, respectively and was 4.1±0.3 days at the fluctuating temperature. Eggs did not develop at 10 °C; however, they could survive a long period of exposure to this temperature. None of two hundred eggs that were placed at a constant temperature of 10 °C for 60 days hatched; but when they were subsequently exposed to ≥ 15 °C, more than 120 of them hatched. Eggs appeared to develop normally at 35 °C, however, larvae died before or immediately after emergence. The lower development threshold temperature for egg, 1st, 2nd, 3rd, 4th larval instars, pupal and all these stages combined was 10.1, 9.5, 9.5, 9.1, 8.2, 8.0, and 9.1 °C, respectively. Degree-day (DD) accumulation was also calculated for each stage as well as for all stages combined. It was estimated to be 189.2±4.8 DD at 12 °C and 207.8±6.9 DD at 30 °C constant, respectively, and 189.1±5.0 DD at fluctuating temperatures.

Temperature influences the development, survival, and life history ofAxinoscymnus apioides Kuznetsov & Ren (Coleoptera: Coccinellidae), a predator of whitefly

The current work was aimed at studying the biology of Axinoscymnus apioides Kuznetsov & Ren (Coleoptera: Coccinellidae) under different temperature regimes. These studies were performed at 6 constant temperature regimes (17, 20, 23, 26, 29, and 32 °C) under laboratory conditions in which A. apioides was fed with Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) nymphs on Hibiscus rosa-sinensis plants. Results indicated that the developmental period for different immature stages decreased with increases in temperature from 17 to 29 °C. The developmental periods of first instar larvae and pupae decreased, while those of second, third, and fourth larval instars increased for the temperature regimes above 29 °C. The survival rates of different larval stages were almost stable at temperatures ranging between 20 and 32 °C. The highest fecundity of A. apioides females (307.80 eggs) was recorded at 23 °C. Based on these results, life tables of A. apioides were constructed for temperatures in the range of 17-29 °C. The innate capacity for increase (rm), the finite rate of increase (λ), and the reproductive rate (R0) reached maximum at 26 °C. The mean length of a generation (T) decreased with increasing temperatures. The lower development thresholds of A. apioides for the total preimaginal development was 9.21 °C, whereas the number of degree-days required for development from egg to adult emergence was 344.83 degree days. The results indicated that the optimal temperature range for A. apioides ranged between 23 and 26 °C.

Influences of Temperature and Ootheca Age on the Life History of the Cockroach Ootheca Parasitoid Aprostocetus hagenowii (Hymenoptera: Eulophidae).

The influences of ootheca age and temperature on the life history of Aprostocetus hagenowii (Ratzeburg) (Hymenoptera: Eulophidae), a gregarious ootheca parasitoid of the American cockroach Periplaneta americana (L.) (Dictyoptera: Blattidae), were evaluated. Oothecae were incubated at 20, 25, and 30 °C to produce oothecae aged 1-60, 1-40, and 1-30 d old, respectively. Fitness traits (development time, percentage emergence, number of progeny, percentage female progeny, and female body size) of A. hagenowii developing in these different-aged oothecae were determined. For oothecae incubated at 20, 25, and 30 °C, parasitoids successfully developed in oothecae aged up to 50, 30, and 20 d old, which represent 72.9%, 65.9%, and 61.9% of the total embryonic development time of P. americana, respectively, without any changes in their fitness traits. When A. hagenowii from oothecae kept at constant temperatures (20, 25, 30, 32, and 35 °C) were compared, the immature development time (71.0-34.0 d) and adult life span decreased with increasing temperature. No parasitoid emerged at 35 °C. The lower, upper, and optimal temperature-dependent developmental thresholds were 9.5, 34.2, and 31.1 °C, respectively. Thermal constant for total immature development was 666.7 degree-days. Temperature did not affect lifetime realized fecundity and number of oothecae parasitized by females but did influence parasitism activities over time. Sugar-fed females sustained longer periods of high parasitism rates (≥70%) at 20-30 °C (15-30 d) than at 32-35 °C (1-5 d). These results are useful for determining the ootheca age and temperature range optimal for parasitoid rearing and for estimating the effectiveness of biological control by the wasps.

Effects of temperature on the development, reproduction and population growth of Anaphothrips obscurus (Thysanoptera: Thripidae)

Anaphothrips obscurus is a cosmopolitan pest feeding on cereals and other grasses. The effects of constant temperatures on the biology of A. obscurus are not well known. Laboratory studies were conducted to assess the effects of temperature on the development, survival, longevity, fecundity and population parameter of A. obscurus at six constant temperatures (15, 20, 25, 30, 32, 35°C). The hatchability was the lowest at 15°C, the highest at 25°C and no eggs hatched at 35°C. Developmental rates increased linearly as the temperature increased. The lower developmental threshold temperature was 10.6°C and 200 degree-days were required to complete development from egg to adult. Adult longevity decreased with increasing temperature, and ranged from 68.87 d at 15°C to 16.41 d at 32°C. The highest total fecundity occurred at 20°C with 162 eggs per female. The temperature-dependent total fecundity, age-specific oviposition rate, and age-specific survival rate models were described. The intrinsic rate of increase (rm) was significantly higher at 30 and 32°C (0.239 and 0.250) than at other temperatures. This study suggests that optimal developmental and reproductive temperatures for A. obscurus ranges between 25 and 30°C and this may help this species adapt to warmer areas and widen its distribution and potential for damage in response to global warming. These findings will also be useful in developing monitoring programs, population dynamic models, and timing of control measures for A. obscurus.

Temperature‐dependent development of the European larch bark beetle, Ips cembrae

AbstractThe temperature‐dependent development of the European larch bark beetle, Ips cembrae, was studied under long‐day conditions L:D 16:8 at three temperature regimes, 15°C, 20°C and 25°C, using the sandwich plate method. By observing the individual developmental progress, we calculated the developmental times and lower developmental thresholds of one entire generation and various ontogenetic stages. The mean developmental time of one generation was about 120, 64 and 37 days at 15°C, 20°C and 25°C, respectively. The egg stage comprised about 9% of the total development or about 16% of the pre‐imaginal development. The larval stages took about 39% of the entire and about 66% of the pre‐imaginal development. The pupal stage needed about 11% of the total or about 18% of the pre‐imaginal development. The lower developmental threshold for one generation was 11.2°C. The egg stage had the highest lower developmental threshold of 12.0°C, the pupa the lowest of 9.8°C and the total larval stages showed a value of 11.2°C. The thermal requirements for I. cembrae have never been studied in detail before. The results will be a valuable contribution for monitoring and risk assessment models to estimate the beetle's phenology and its potential impacts on forest ecosystems under changing climate conditions.

Effect of Temperature on Growth, Reproductive Activity, and Survival of the Invasive Bromeliad-Eating WeevilMetamasius callizona(Coleoptera: Curculionidae)

Abstract Growth, oviposition, and survival rates of the bromeliad-eating weevil Metamasius callizona (Chevrolat) (Coleoptera: Curculionidae) were measured at a range of temperatures to determine optimal temperature range, lower and upper development thresholds, and degree-days needed for development of immature stages. Optimal temperature range for growth was 25 to 30 °C and for oviposition 22 to 33 °C. The lower development threshold was 13 °C and upper threshold about 35 °C. Development of the egg and larval stages required 518 degree-days, and from pupation to adult 140 degree-days. Adult weevils suffered higher mortality at 35 °C than at 25 or 16 °C. Typical winter conditions likely have at most a minimal effect on weevil populations in central Florida and no effect in southern Florida. As well, high summer temperatures could potentially cause weevil mortality due to heat stupor but, as with winter temperatures, the effects would be minimal. Extremely cold winters and extremely high summer temperature...

Temperature-dependent development of pale damsel bug, Nabis capsiformis Geramer (hemiptera: nabidae) using linear and non-linear models

Temperature can affect the predation potential of predators. The temperature-dependent development of Nabis capsiformis (Geram) was studied in the laboratory in six constant temperatures (18, 22, 24, 28, 31 and 33 °C) on green pods of bean (Phaseolus vulgaris, L.) infested with pea aphid, Acyrthosiphon pisum (Harris). Developmental times in days for separate immature and total development (egg to adult) were inversely proportional to temperature between 18 and 28 °C but increased at 31 °C. Bugs did not manage to complete development at 33 °C. Thermal parameters were estimated by fitting two linear (common and Ikemoto- Takai) models and four non-linear (Taylor, Hilbert – Logan, Briere and Lactin) models to the data. The lower developmental thresholds, calculated using the common linear model and Ikemoto- Takai model for egg, total nymph, and total development were 15.91, 10.01, and 11.76 °C and 14.74, 10.55, and 12.07 °C respectively. The thermal constants for total development were estimated 341.29° – days with common linear model and 313.40° – days with Ikemoto – Takai model. Four non linear models, Taylor, Hilbert and Logan, Briere and Lactin fitted the data well as measured by the ‘‘z weight’’ indicator. Temperature threshold parameters for these non linear models (T(min), T(opt), and T(max)) were estimated for eggs, total nymphal stages, and total development time (egg to adult). The Taylor model is recommended for the description of temperature-dependent development of N. capsiformis. The optimal temperature for the development of eggs, the five nymphal instars and the egg-adult period predicted by this model ranged between 29 and 30 °C. Results from this study will provide basic information for the development of predictive models of the seasonal progress of this natural enemy.

Survival and development of Amblypelta nitida Stål, A. l. lutescens Distant (Hemiptera: Coreidae) and the egg parasitoid, Anastatus sp. (Hymenoptera: Eupelmidae) at constant rearing temperatures

The effects of constant rearing temperatures on the development and survival of Amblypelta nitida, Amblypelta lutescens lutescens (Hemiptera: Coreidae) and their egg parasitoid, Anastatus sp. (Hymenoptera: Eupelmidae), were studied in the laboratory. Amblypelta nitida and A. l. lutescens survival and development were studied at 10, 15, 20, 25, 30 and 35°C. The development rate of both species increased linearly with increasing temperature but insects only developed to adults at 20, 25 and 30°C; at these temperatures, mean development times for A. nitida were 87, 64 and 29days and for A. l. lutescens they were 93, 65 and 31days respectively. No eggs of either species hatched at 10°C and only A. l. lutescens eggs hatched at 35°C. At all temperatures at which insects developed beyond the first instar, mortality rates were highest in the second instar for both species. Lower developmental threshold temperatures to complete development were 15.9°C and 17.1°C for A. nitida and A. l. lutescens respectively; A. nitida required 421 degree-days and A. l. lutescens required 404 degree-days to complete development. Anastatus sp. completed development at all six study temperatures and development times decreased from 54days at 17.5°C to 16days at 30°C; similarly Anastatus sp. survival increased with increasing temperature. The lower developmental threshold temperature and degree-days required for Anastatus sp. to complete development were 15.0°C and 234 degree-days respectively. Results are discussed with respect to the different geographical distributions of A. nitida and A. l. lutescens and likely interactions with Anastatus sp.

Thermal requirements and development of the Korean population of the potato leafminer, Liriomyza huidobrensis (Diptera: Agromyzidae)

The development of Liriomyza huidobrensis (Blanchard), is an important pest of potato, was examined at six constant temperatures (10, 15, 20, 25, 27 and 30°C) on kidney bean, Phaseolus vulgaris L. Results showed the temperature-related ecological niche of L. huidobrensis might be narrow. The total development period (egg to adult) decreased with increasing temperature from 15–27°C, although no egg hatched at 10°C and no pupae survived at 30°C. The linear model estimated the lower developmental threshold of eggs, larvae, pupae, and total immature stage as 10.17, 10.37, 9.08 and 9.64°C, respectively, and the thermal requirement as 34.54, 65.51, 137.62 and 247.04 degree-days (DD), respectively. The development rates were fitted to Lactin's nonlinear model, and the lower, upper, and optimal temperatures for development were estimated as 9.8, 30.0 and 26.0°C, respectively. Female sex ratio of the surviving individuals was 0.62. Thermal requirements and temperature thresholds can be used to forecast the occurrence, number of generations, and population dynamics of L. huidobrensis.

Temperature-Mediated Growth Thresholds of Acrobasis vaccinii (Lepidoptera: Pyralidae).

Degree-day models link ambient temperature to the development of insects, making such models valuable tools in integrated pest management. These models increase management efficacy by quantifying and predicting pest phenology. In Wisconsin, the top insect pest of cranberry production is the cranberry fruitworm, Acrobasis vaccinii Riley (Lepidoptera: Pyralidae). Control of this species is often complicated by the fact that the larvae feed entirely within the fruit. Timing of control tactics, therefore, is critical and generally targets the adult and egg stages. However, the commencement of oviposition and egg hatch are extremely difficult to track empirically, forcing pest management strategies to rely on proxy events that are more apparent but less informative as indicators of cranberry fruitworm egg presence. This research provides the upper and lower temperature-mediated growth thresholds of this pest, which represents the first steps toward the creation of a degree-day model. Using field-collected A. vaccinii, we reared the larvae within cranberry fruit and monitored larval growth at nine different constant temperatures. We determined the average growth rate at each temperature and modeled growth rates as a function of temperature. We then calculated the precise upper and lower developmental temperature thresholds of this species. Future work will be able to use these thresholds to generate degree-day accumulations that correspond to phenological events in the field, providing a powerful predictive tool for pest management in cranberry production.

Temperature-Dependent Development Modeling of the Phorid Fly Megaselia halterata (Wood) (Diptera: Phoridae).

The effect of temperature on the development of Megaselia halterata (Wood) (Diptera: Phoridae) on A15 variety of button mushroom in the stages of casing and spawn-running was investigated at eight constant temperatures (10, 12.5, 15, 18, 20, 22.5, 25, and 27°C) and developmental rates were modeled as a function of temperature. At 25 and 27°C, an average of 22.2 ± 0.14 and 20.0 ± 0.10days was needed for M. halterata to complete its development from oviposition to adult eclosion in the stages of casing and spawn-running, respectively. The developmental times of males or females at various constant temperatures were significantly different. Among the linear models, the Ikemoto and Takai linear model in the absence of 12.5 and 25°C showed the best statistical goodness-of-fit and based on this model, the lower developmental threshold and the thermal constant were estimated as 10.4°C and 526.3degree-days, respectively. Twelve nonlinear temperature-dependent models were examined to find the best model to describe the relationship between temperature and development rate of M. halterata. The Logan 10 nonlinear model provided the best estimation for T opt and T max and is strongly recommended for the description of temperature-dependent development of M. halterata.

Life history of the spider parasitoid Zatypota percontatoria (Hymenoptera: Ichneumonidae)

AbstractThe life history of polysphinctine parasitoids is poorly understood. As a result, their effect on their host has not been evaluated. Here, we present the phenology of Zatypota percontatoria, an ectoparasitoid wasp of theridiid spiders, using rich field, semi‐field and laboratory investigations of selected life‐history parameters. The wasps overwintered as larva attached to the spider abdomen and the imagos of the first generation emerged at the beginning of May. The sex ratio (F/M) of overwintered wasp larvae was 1.4. The wasp spent an average of 6.4 days in the egg stage, 27.67 days in the larval stage and 9.6 days in the pupal stage. Adult longevity was on average 14.34 days. Oviposition occurred on average 8.44 days following maturity. The wasp laid on average 0.35 eggs/day. The total fecundity was on average 7.4 eggs per wasp and decreased with age (data from unmated females). The developmental rate increased with experimental temperature up to 28 °C. The lower developmental threshold for pupae was estimated at 6.6 °C. The sum of effective temperatures for pupae was estimated at 157.8 degree days. Using daily temperature records from the Czech Republic over the last 41 years, we estimated an average of 3.5 generations of Z. percontatoria per year. Mortality was 48% in semi‐field conditions and 23% in the laboratory. The incidence of mortality was highest during egg and larval stages caused by the detachment of eggs or larvae during spider molting, the mortality of the spider‐host and egg deposition on the spider prosoma.

Evaluation of the phenological synchrony between potato crop and Colorado potato beetle under future climate in Europe

Europe is one of the world’s largest food producers, and climate change may pose a serious threat to food security in the region. In the present study, we assess the potential impact of climate change on the Colorado Potato Beetle (CPB), Leptinotarsa decemlineata (Say)—a severe pest of potato (Solanum tuberosum, L.). We also investigate the possible impact of climate change on the phenological development of potato. The main focus is on factors that may limit the northward expansion of the CPB, and the number of generations per year in areas where the insect pest is already present. These factors include lack of temperature sum for completed development before winter, and lack of food (i.e. potato) due to mismatches in insect-host plant phenological synchrony.We use a gridded observational dataset and an ensemble of bias corrected regional climate model data for the period of 1981–2099, representing RCP8.5, as input to a potato and CPB phenological model. The results show that in the future, CPB individuals with a low developmental threshold (+10°C) can complete maturity of two generations per year before potato is harvested in most parts of Europe. A third generation of CPB may not be able to complete maturation due to lack of food in south and central Europe, while temperature becomes a limiting factor further north. In north-eastern Europe, the initiation of a first generation may be delayed due to lack of food in spring. CPBs with a high developmental threshold (+12°C) will emerge later from winter hibernation, and food availability will therefore not be a problem in spring. However, individuals with a high developmental threshold face a greater risk of regeneration failure caused by harvesting of potato in autumn. The potential lack of food in autumn may also increase the strength of selection towards a low developmental threshold in northern populations. The combined analysis of CPB and potato phenology indicated that climate change can lead to increased pressure from the CPB in most potato growing areas.

Life table analysis under constant temperature for Opisina arenosella (Lepidoptera: Xyloryctidae), an invasive moth of palm plants

AbstractThe coconut black‐headed caterpillar Opisina arenosella Walker, which is spreading in Southeast Asia and southern China, is a significant pest of palm trees. All life stages of this species were reared at 20, 23, 26, 29, 32 and 35 °C to understand the effect of temperature on the biology of O. arenosella. Total developmental time egg to adult generally was longest (≈114 days) at 20 °C, declined significantly with increasing temperature, and shortest (≈47 days) at 32 °C. Estimated lower developmental threshold temperature was 11.5 °C, and estimated effective accumulated temperature was 996.93°days. A third‐order polynomial model estimated an optimal temperature of 32 °C for development. The predicted number of generations per year was calculated as 4–5 under average climatic conditions experienced in Hainan, China. The oviposition period ranged from 2 to 4 days and was longest at 26 °C while fecundity ranged from 30 to 180 total eggs laid per female and was greatest at 32 °C. The highest reproductive values were found at 32 °C. At this temperature, net reproductive rate (R0), generation time (T), intrinsic rate of increase (rm), finite rate of increase (λ) and doubling time (DT) were 64, 45 days, 0.09, 1.1 and 7.6 days, respectively. Knowledge of the effect of temperature on the life history characteristics of Opisina arenosella can be used to predict population growth, develop pest management strategies and mass produce insects for production of biocontrol agents.