Number Of Degree-days Research Articles

Temperature can limit the invasion range of the ambrosia beetle Euwallacea nr. fornicatus

Abstract Temperature heavily affects the development rate of insects. Until temperatures become too extreme, insects will generally experience greater rates of development at higher temperatures and slower rates of development at lower temperatures. The invasive ambrosia beetle Euwallacea nr. fornicatus Eichhoff, referred to as the polyphagous shot hole borer (PSHB), was tested for development rates at a range of temperatures between 15 and 32 °C. Based on the development rates recorded, it was calculated that the tmin, tmax and topt were 13.34, 33.08 and 27.51 °C, respectively. The number of degree days required for PSHB to complete development from egg to adult was estimated to be approximately 398 degree days. These results can be used to predict the potential distribution of PSHB, as well as where climatic factors may limit their establishment. Furthermore, the development information can be of use when predicting an increase in beetle activity.

Nitrogen (N) Dynamics in the Mineral Soil of a Central Appalachian Hardwood Forest During a Quarter Century of Whole-Watershed N Additions

The structure and function of terrestrial ecosystems are maintained by processes that vary with temporal and spatial scale. This study examined temporal and spatial patterns of net nitrogen (N) mineralization and nitrification in mineral soil of three watersheds at the Fernow Experimental Forest, WV: 2 untreated watersheds and 1 watershed receiving aerial applications of N over a 25-year period. Soil was sampled to 5 cm from each of seven plots per watershed and placed in two polyethylene bags—one bag brought to the laboratory for extraction/analysis, and the other bag incubated in situ at a 5 cm depth monthly during growing seasons of 1993–1995, 2002, 2005, 2007–2014. Spatial patterns of net N mineralization and nitrification changed in all watersheds, but were especially evident in the treated watershed, with spatial variability changing non-monotonically, increasing then decreasing markedly. These results support a prediction of the N homogeneity hypothesis that increasing N loads will increase spatial homogeneity in N processing. Temporal patterns for net N mineralization and nitrification were similar for all watersheds, with rates increasing about 25–30% from 1993 to 1995, decreasing by more than 50% by 2005, and then increasing significantly to 2014. The best predictor of these synchronous temporal patterns across all watersheds was number of degree days below 19°C, a value similar to published temperature maxima for net rates of N mineralization and nitrification for these soils. The lack of persistent, detectable differences in net nitrification between watersheds is surprising because fertilization has maintained higher stream-water nitrate concentrations than in the reference watersheds. Lack of differences in net nitrification among watersheds suggests that N-enhanced stream-water nitrate following N fertilization may be the result of a reduced biotic demand for nitrate following fertilization with ammonium sulfate.

Combining public participatory surveillance and occupancy modelling to predict the distributional response of Ixodes scapularis to climate change

Ixodes scapularis, a known vector of Borrelia burgdorferi sensu stricto (Bbss), is undergoing range expansion in many parts of Canada. The province of New Brunswick, which borders jurisdictions with established populations of I. scapularis, constitutes a range expansion zone for this species. To better understand the current and potential future distribution of this tick under climate change projections, this study applied occupancy modelling to distributional records of adult ticks that successfully overwintered, obtained through passive surveillance. This study indicates that I. scapularis occurs throughout the southern-most portion of the province, in close proximity to coastlines and major waterways. Milder winter conditions, as indicated by the number of degree days <0 °C, was determined to be a strong predictor of tick occurrence, as was, to a lesser degree, rising levels of annual precipitation, leading to a final model with a predictive accuracy of 0.845 (range: 0.828–0.893). Both RCP 4.5 and RCP 8.5 climate projections predict that a significant proportion of the province (roughly a quarter to a third) will be highly suitable for I. scapularis by the 2080s. Comparison with cases of canine infection show good spatial agreement with baseline model predictions, but the presence of canine Borrelia infections beyond the climate envelope, defined by the highest probabilities of tick occurrence, suggest the presence of Bbss-carrying ticks distributed by long-range dispersal events. This research demonstrates that predictive statistical modelling of multi-year surveillance information is an efficient way to identify areas where I. scapularis is most likely to occur, and can be used to guide subsequent active sampling efforts in order to better understand fine scale species distributional patterns.

Flights of Gray Looper (Rachiplusia ou) (Noctuidae) and Soybean Looper (Chrysodeixis includens) (Noctuidae) in Southeast Missouri Soybean

Noctuid moths include economic species of importance such as the soybean podworm, black cutworm, soybean looper, and fall armyworm. The gray looper feeds on a wide variety of low-growing plants including tobacco, soybean, cotton, clover, and common wheat. Soybean looper can likewise be found in soybean and cotton. To monitor the flights and numbers of gray and soybean loopers in Southeast Missouri, funnel traps were baited with Autographa gamma or Pseudoplusia includens lures and dispensed on 1 May 2015 in 8 randomly selected soybean fields. Traps were monitored weekly (1 May - 1 Oct 2015). Degree days began at biofix, and a single sin method with a lower threshold of 15˚ was used to calculate accumulative degrees days. Temperature data was obtained from NOAA. Each peak flight was assigned accumulative number of degree days. Degree days for the current soybean looper model (egg to adult, 435dd) were compared with estimated models for gray and soybean loopers. These models were developed by averaging accumulated degree days between counties for peaks 1 -4 (204, 496, 937, and 1527 degree-days, gray looper) and for peaks 1 – 5 (349, 641, 962, 1258, and 1540 degree days, soybean looper). Soybean looper model was accurate for flights 1 – 3 for gray looper. For soybean looper management, the new soybean looper model worked best for estimating future peak flights. This confirmation of model data should help growers with their insecticide application decisions.

A fungal endophyte consortium counterbalances the negative effects of reduced nitrogen input on the yield of field-grown spring barley

SUMMARYThe use of chemicals to fertilize crops incurs economic and environmental costs and it is widely recognized that the current level of chemical fertilizer use is unsustainable in many intensive farming systems. Any methods that can reduce fertilizer input and still maintain acceptable yields would be of great benefit to both the farmer and the environment. The use of beneficial endophytes as crop inoculants may go some way towards improving crop yields beyond that achievable using fertilizer increases alone. Field trials were conducted over two seasons on three contrasting field sites to test the effects of fungal endophytes from a wild barley relative on three barley cultivars (Mickle, Planet and Propino). Seeds were either untreated or dressed with a consortium of four endophyte strains, and three levels of nitrogen (N) were applied to both treatments: full N, 50% N and 0 N. On the field site with the lowest overall N input, the endophyte treatment with 50% N restored yield for ‘Planet’ to that associated with untreated plants receiving the full N input. On the same site and with the same cultivar, endophyte treatment increased yield by 15% under full N, and by a mean 12% for all three cultivars with 50% N input. Over both seasons and all three sites, the endophyte treatment increased yield for the cultivar Planet by a mean of 9%. For the endophyte-associated increase in the variety Planet grain yield over the untreated trials strong correlations were found between increased yield and each of low rainfall, greater evaporation and greater number of degree days above the base. Furthermore, the efficacy of the endophytes was not removed by regular foliar fungicidal treatment. These results suggest that fungal endophytes can contribute to improving barley yield grown in low rainfall areas and under a range of fertilizer input regimes, provided that endophyte treatments are applied to compatible crop cultivars and sites.

Thermal effects on development and adult longevity of endoparasitoid Chelonus murakatae Munakata (Hymenoptera: Braconidae).

The effects of temperature on the development duration and longevity of adult of Chelonus murakatae were studied under five constant temperatures including 22.5, 25, 27.5, 30 and 32.5±0.5°C under laboratory conditions. It was observed that the development time was inversely proportional to the temperature within the range of 22.5 to 32.5°C. The results indicated that the optimum temperature for development ranged from 25 to 30°C. Thermal threshold was estimated by a linear model which was recorded as 15.5 and 18.5°C for males and females, respectively. Number of degree days required to complete the development from egg to adult were 439.6 degree days in males and 336.8 degree days in females. Adult longevity also decreased with increase in temperature. This information can be used for optimizing mass culturing and field release for an efficient biological control of Chilo suppressalis in this specie.

A DNA vaccine encoding the viral hemorrhagic septicemia virus genotype IVb glycoprotein confers protection in muskellunge (Esox masquinongy), rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and lake trout (Salvelinus namaycush).

BackgroundThe viral hemorrhagic septicemia virus (VHSV) is one of the most serious fish pathogens. In 2003, a novel sublineage (genotype IVb) of this deadly virus emerged in the Great Lakes basin causing serious fish kills. We have previously demonstrated that a DNA plasmid (pcDNA), containing a cytomegalovirus (CMV) promoter and the viral hemorrhagic septicemia virus (VHSV) genotype IVb glycoprotein (G) gene insert (designated pVHSivb-G) confers moderate protection in muskellunge (Esox masquinongy), a highly susceptible species upon challenge. In order to achieve optimal protection, we investigated a number of factors including the incubation time [i.e. the number of degree days (° days)] before challenge, and viral challenge dose and route. Additionally, we tested if pVHSivb-G provides protection against VHSV-IVb to less susceptible salmonids such as rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta) and lake trout (Salvelinus namaycush).ResultsAn increase in the period lapsed between vaccination and challenge to 1880° days resulted in 95% relative percent protection (RPS) in muskellunge following a single administration of the pVHSivb-G plasmid and viral challenge. An RPS of 100% for muskellunge was achieved with a longer incubation period (2400° days) and in conjunction with a booster dose of the plasmid. The pVHSivb-G vaccine also elicited significant protection in all three salmonid species, reaching 100% RPS in lake trout following an incubation period of 1001° days prior to viral challenge. Vaccination with pVHSivb-G was also associated with the development of significant levels of circulating VHSV-binding antibodies in muskellunge as measured by indirect ELISA, which reached peak levels 6–7 weeks post-vaccination. Viral shedding in vaccinated survivors was minimal and of transient nature.ConclusionsThe study shows that the pVHSivb-G plasmid can elicit a protective response against the wild virus strain in a range of species important in recreational and commercial Great Lakes fisheries.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0662-8) contains supplementary material, which is available to authorized users.

Effect of degree-days of fasting stress on rainbow trout, Oncorhynchus mykiss

Most farm animals are fasted before slaughter to empty the digestive system but in fish, the appropriate fasting time also depends on the water temperature. To analyze how the physiological and haematological response vary with degree-days (°C days), 180 rainbow trout (Oncorhynchus mykiss) were fasted for 1, 2 or 3days in two different trials with water at 22.7 or 11.1°C. In general, water temperature had a significant influence on most variables measured, although the number of degree days had a less important effect on trout physiological response, being only important in the depletion of reserves rate. The condition factor decreased at 2 and 3days of fasting. At warmer temperatures (22.7°C), relative weight of the gut content, hepatosomatic index and plasma levels of glucose were lower while cortisol, lactate and haematocrit were higher than at colder ones (11.1°C). Fasting up to 68°Cdays did not seem to have a negative effect on stress but a high water temperature above 20°C was stressful for trout. Statement of relevanceThis paper present data on the effect of the number of degree days of fasting on body measurements and the haematological response of rainbow trout prior to slaughter. Fasting up to 68 degree days did not have a major effect on their welfare and that their haematological response was solely affected by the water temperature and not by food deprivation

The effect of cyanamide on budbreak and vine development of Thompson Seedless grapevines in the San Joaquin Valley of California

Cyanamide (H 2 CN 2 ) was applied to dormant canes on Thompson Seedless grapevines grown in the field to determine its effect on budbreak and subsequent vine development. A 2.5 % (v/v) solution of cyanamide was sprayed on vines just subsequent to pruning in a 2 year study. Vines pruned and treated with cyanamide on January 17 had budbreak 3 and 7 d earlier than the pruned only controls in 1984 and 1985, respectively. The same treatment imposed on March 1 delayed budbreak when compared with the control vines. There were differences of 3 and 6 d between the dates of 50 % bloom for the treatments with the earliest and latest dates of budbreak in both years. The number of degree days > 10 °C between budbreak and bloom averaged 365 and 372 °C · d for all treatments in 1984 and 1985, respectively. There were no significant differences in fruit maturation characteristics such as berry weight and soluble solids concentration among treatments in both years. Results indicate that cyanamide can be used to alter the date of budbreak which subsequently affects bloom date of Thompson Seedless grapevines. However, factors other than those two phenological events become more important in determining fruit maturation of this variety when grown in the San Joaquin Valley of California.

Laboratory and field-based temperature-dependent development of a monophagous weevil: Implications for integrated weed management

The stem-boring weevil, Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) was imported from Asia to North America and approved for release as a classical biological control agent for the invasive annual vine Persicaria perfoliata (L.) H. Gross (Polygonaceae) in 2004. Its impact on the weed has been somewhat variable, depending in part on environmental conditions. We reared R. latipes in environmental chambers at different temperatures to determine the lower developmental threshold and number of degree days required for development. Results, along with known R. latipes reproductive parameters, were used to develop a simple population model, and compared to field data from sites that had been intensively monitored from 2008 to 2010. The lower developmental threshold was estimated at 10.2°C. On average, 358 degree days (°C) were required for development from egg to adult, with an additional 139 degree days needed for the preoviposition period. Field sites had relatively high P. perfoliata cover and low R. latipes densities in 2009 compared to either 2008 or 2010. Based on degree-day accumulations for these three years, the population model estimated that fewer than half the number of weevils would have been produced by the end of the season in 2009 as in 2008, and only about a quarter as many as in 2010. Substantially higher rainfall during April–June 2009 compared to 2008 and 2010 probably also helped promote more abundant P. perfoliata cover in 2009.

An algorithmic calibration approach to identify globally optimal parameters for constraining the DayCent model

The accurate calibration of complex biogeochemical models is essential for the robust estimation of soil greenhouse gases (GHG) as well as other environmental conditions and parameters that are used in research and policy decisions. DayCent is a popular biogeochemical model used both nationally and internationally for this purpose. Despite DayCent's popularity, its complex parameter estimation is often based on experts’ knowledge which is somewhat subjective. In this study we used the inverse modelling parameter estimation software (PEST), to calibrate the DayCent model based on sensitivity and identifiability analysis. Using previously published N2O and crop yield data as a basis of our calibration approach, we found that half of the 140 parameters used in this study were the primary drivers of calibration differences (i.e. the most sensitive) and the remaining parameters could not be identified given the data set and parameter ranges we used in this study. The post calibration results showed improvement over the pre-calibration parameter set based on, a decrease in residual differences 79% for N2O fluxes and 84% for crop yield, and an increase in coefficient of determination 63% for N2O fluxes and 72% for corn yield. The results of our study suggest that future studies need to better characterize germination temperature, number of degree-days and temperature dependency of plant growth; these processes were highly sensitive and could not be adequately constrained by the data used in our study. Furthermore, the sensitivity and identifiability analysis was helpful in providing deeper insight for important processes and associated parameters that can lead to further improvement in calibration of DayCent model.

Predicting adult emergence of Dakota skipper and Poweshiek skipperling (Lepidoptera: Hesperiidae) in Canada

Dakota skipper (Hesperia dacotae Skinner) and Poweshiek skipperling (Oarisma poweshiek Parker) (Lepidoptera: Hesperiidae) are endemic prairie species that are threatened in Canada. Surveys during the brief adult flight period are necessary to quantify population sizes, but dates of adult emergence vary widely from year to year (up to 24 days) and populations are geographically distant from one another (150–250 km). To predict adult emergence of H. dacotae and O. poweshiek, we used local weather station data to calculate the number of degree days accumulated between March 1 and adult emergence using two different models in seven different years between 2002 and 2013. We also compared the number of degree days accumulated at the soil surface where larvae and pupae reside to those accumulated using weather station data. We recommend that surveys for Dakota skipper begin when degree day accumulations (from weather stations) reach a threshold of 575 (standard model) or 600 (double sine model) in the south central portion of Manitoba and 550 (standard model) or 575 (double sine model) in the southwest region of Manitoba. For Poweshiek skipperling surveys should be considered after degree day accumulations reach 575 (standard model) or 625 (double sine model). Degree days accumulated at the soil surface were 20–30 % greater than those calculated using weather station data in Dakota skipper sites, and 1–12 % greater in Poweshiek skipperling sites. Using our models, we predicted adult emergence to within 48 h of emergence in 2011, 2012 and 2013.

Insect-induced tree mortality of boreal forests in eastern Canada under a changing climate.

Forest insects are major disturbances that induce tree mortality in eastern coniferous (or fir-spruce) forests in eastern North America. The spruce budworm (SBW) (Choristoneura fumiferana [Clemens]) is the most devastating insect causing tree mortality. However, the relative importance of insect-caused mortality versus tree mortality caused by other agents and how this relationship will change with climate change is not known. Based on permanent sample plots across eastern Canada, we combined a logistic model with a negative model to estimate tree mortality. The results showed that tree mortality increased mainly due to forest insects. The mean difference in annual tree mortality between plots disturbed by insects and those without insect disturbance was 0.0680 per year (P < 0.0001, T-test), and the carbon sink loss was about 2.87t C ha−1 year−1 larger than in natural forests. We also found that annual tree mortality increased significantly with the annual climate moisture index (CMI) and decreased significantly with annual minimum temperature (Tmin), annual mean temperature (Tmean) and the number of degree days below 0°C (DD0), which was inconsistent with previous studies (Adams et al. 2009; van Mantgem et al. 2009; Allen et al. 2010). Furthermore, the results for the trends in the magnitude of forest insect outbreaks were consistent with those of climate factors for annual tree mortality. Our results demonstrate that forest insects are the dominant cause of the tree mortality in eastern Canada but that tree mortality induced by insect outbreaks will decrease in eastern Canada under warming climate.

Phenology, life table analysis and temperature requirements of the invasive brown marmorated stink bug, Halyomorpha halys, in Europe

The invasive Halyomorpha halys was accidentally introduced into Switzerland around 2004 and has recently established in the neighbouring countries of France and Italy. To better understand the population dynamics of this pest in Europe, the phenology, reproductive biology and temperature requirements of Swiss H. halys populations were investigated. Overwintered adults became active in April, but peak oviposition was not observed before early July. Individual females laid on average 79 eggs (maximum of 160). The oviposition period lasted from mid-June to end of September. Eggs laid in August and September did not result in offspring due to the low temperatures in autumn. Under natural fluctuating temperatures, development from egg to adult lasted between 60 and 131 days. The first new generation of adults did not occur before mid-August when the photoperiod was already below 15 h, which likely initiated diapause and suppressed the reproductive activity of new generation adults. Under controlled conditions of 20, 25 and 30 °C, Swiss H. halys populations developed within 75.8, 42.3 and 33.2 days from egg to adult, respectively. No development was possible at or below 15 and at or above 35 °C. The number of degree days required for completion of development from egg to adult was 588.24 DD. Under semi-natural conditions, total mortality of Swiss H. halys populations was 86.7 % with a net reproductive rate of 5.69, indicating growing populations. In Switzerland, H. halys is univoltine, but if it continues to spread into the Mediterranean area two generations per year could be expected.

Observations on the life cycle of potato cyst nematodes, Globodera rostochiensis and G. pallida, on early potato cultivars

Potato cyst nematodes (PCN) are the most economically important nematode pests of potato. Early harvesting is part of a preventive management approach for very early potato varieties. In Belgium, tubers are harvested before 20 June because it is assumed that no cyst formation occurs by that date. However, this assumption might not be valid any more because of climate change, the availability of new cultivars (with new traits), and the increasing prevalence of Globodera pallida. Therefore, pot, microplot and field trials were conducted to study the life cycle of PCN in early potato-growing conditions. The development of populations of G. pallida on three potato cultivars, Eersteling (susceptible to PCN), Première (resistant to G. rostochiensis) and Ambassador (partially resistant to G. pallida) and that of G. rostochiensis on cv. Eersteling was monitored in the growth chamber with simulation of field temperatures of the season. On cvs Eersteling and Première, second-stage juveniles (J2), males, females and cysts of G. pallida populations were found 28, 56, 63 and 77 days after infestation with cysts (DAI), respectively. The number of degree days (DD) for G. pallida to complete its life cycle using a base temperature of 4°C was calculated 450 DD4. On cv. Ambassador, females of G. pallida were never observed. J2, males, females and cysts of G. rostochiensis were detected 42, 70, 70 and 84 DAI, respectively. This species needed 398 DD6 at a base temperature of 6°C to complete its life cycle. Observations in two fields and in microplots under prevailing weather conditions in 2013 revealed that cysts of G. pallida and G. rostochiensis were formed on June 12, when the accumulated degree days were 463 DD4 and 401 DD6, respectively. Our observations show that both species of Globodera develop earlier than was assumed based on previous data. Therefore, harvesting based on the accumulated heat above the basal development temperature required by PCN species can replace the set harvest date.

Life cycle and damage of the root-knot nematode Meloidogyne minor on potato, Solanum tuberosum

Meloidogyne minor is a root-knot nematode reported in Belgium, Ireland, The Netherlands, Portugal, United Kingdom, Chile and the United States. It is found in sport fields and golf courses where it causes the yellow patch disease. However, M. minor has also been detected in potato fields in The Netherlands and the UK and may pose a threat for potato cultivation. Therefore, the life cycle and damage of M. minor on potato cv. Bintje were examined under controlled conditions. To assess its life cycle, young potato plants were inoculated with freshly hatched second-stage juveniles (J2). The developmental stages of M. minor were recorded at weekly intervals after inoculation until second generation J2 were detected. One week after inoculation, only vermiform juveniles were found in the roots. All juveniles were swollen after 3 weeks and the first adult females were observed. Egg masses were seen after 6 weeks together with second generation J2. The number of degree days for M. minor to complete its life cycle was calculated using a base temperature of 5°C (DD5); between 606 and 727 DD5 were needed to complete the life cycle. Damage development of M. minor on potato was examined in a pot experiment with different inoculation densities. Symptoms (galling on the tubers) were similar to those caused by M. chitwoodi and M. fallax. At initial population densities () of 10 J2 (100 cm3 soil)−1 and more, tubers showed galls. Severely damaged potato tubers were observed at (100 cm3 soil)−1 and a damage threshold of 41 J2 (100 cm3 soil)−1 was calculated. An in vitro test showed that five, commonly grown, potato cultivars were good hosts for M. minor. Based on our results, M. minor is able to develop on potato and cause severe damage at low initial population densities. Therefore, further spread of this nematode in agricultural fields should be avoided.

Estimates of downed woody debris decay class transitions for forests across the eastern United States

Large-scale inventories of downed woody debris (DWD; downed dead wood of a minimum size) often record decay status by assigning pieces to classes of decay according to their visual/structural attributes (e.g., presence of branches, log shape, and texture and color of wood). DWD decay classes are not only essential for estimating current DWD biomass and carbon stocks, but may also facilitate the prediction of future DWD attributes. Estimating temporal transitions between decay classes may provide a mechanism for projecting DWD attributes in forest ecosystems. To date, modeling decay class transitions for individual DWD pieces has not been fully explored in this context. The goal of this study was to use a repeated DWD inventory across the eastern US to estimate decay class transitions to inform DWD dynamics across this broad geographic region.Using matched and non-matched DWD from the repeated inventory, ordinal regression techniques were used to estimate the five-year probability of a DWD piece remaining in the same decay class or moving into more advanced decay classes. Models indicated that these transitions were largely related to DWD piece length and climatic regime, as transitions occurred more slowly for longer DWD pieces located in regions with a low number of degree days (a climatic variable serving as a proxy for decomposition potential). Cumulative link mixed models allowed the estimation of forest type-specific effects (i.e., random effects) on the DWD transition process. Hardwood species transitioned into subsequent decay classes more rapidly than softwoods. Model assessments indicated that the correct decay class observed after five years was correctly predicted for approximately 50–70% of observations, but was dependent on forest type and initial decay class.Results differed depending on the models under examination. For example, using the matched data, the average number of classes moved per five years was 1.28±0.07 (mean±SE) classes for decay class 1 logs found in spruce-fir forests, however, using the matched plus non-matched data, the average number of classes moved per five years was 3.51±0.19 for these same logs. These two model sets (matched and matched plus non-matched DWD pieces) may denote upper and lower bounds for DWD decay class transition rates. Analyses presented herein provide an initial assessment of DWD decay across eastern US forests and thus provide quantitative tools that apply to emerging bioenergy questions and associated DWD dynamics research. Developed models, coupled with traditional forest productivity simulation tools, may be used in the future to determine accurate estimates of future forest C stocks.

Biological parameters of Elasmus nudus (Hymenoptera, Eulophidae), a parasitoid of the pistachio fruit hull borer moth, Arimania komaroffi (Lepidoptera, Pyralidae)

Elasmus nudus (Nees) is known as a synovigenic, gregarious ectoparasitoid of the pistachio fruit hull borer moth, Arimania komaroffi Ragonot in pistachio plantations in southern Iran. The biological parameters of this parasitoid were studied using the Mediterranean flour moth, Ephestia kuehniella Zeller as a host and the resulting data were compared with that of its native host, A. komaroffi. The parasitoid developed successfully from egg to adult over a temperature range of 17–35°C. The developmental times of the parasitoid on A. komaroffi and E. kuehniella were not significantly different. The threshold value at which the development rate of E. nudus was zero was estimated to be 9.2°C and the estimated number of degree days (°D) for development from egg to adult was 238 above this threshold. The reproductive potential of E. nudus was similar on both hosts at 30°C. The intrinsic rate of natural increase (r m ) for E. nudus did not vary much between 25°C and 32.5°C. In addition, the clutch size of the parasitoid on the two hosts was not statistically different. The present study provides some basic information on the biological characteristics of E. nudus.

Practical versus theoretical domestic energy consumption for space heating

Methods to calculate the theoretical energy consumption consider several things: the number of degree days per year that need to be compensated by heating, the characteristics of the dwelling, the number of occupants and the characteristics of the installation for space heating and sanitary hot water. However, these methods do not take into account consumer behaviour, which may affect the actual consumption.The theoretical calculation methods are based on assumptions and use a number of standardized parameters.The difference between the actual and the theoretical energy consumption, and the impact of the residents' behaviour on energy consumption, is analysed by means of a literature study and a practical research. An energy advice procedure (EAP) audit is executed in five dwellings, as well as a survey regarding the energy related behaviour of the households. The theoretically calculated consumption is compared with the billed actual energy consumption of the families. The results show some problems with the current procedure and give some options to improve it. Some research needs are identified to gain more insights in the influence of different behavioural factors on the actual energy use for heating.

Can snow depth be used to predict the distribution of the high Arctic aphid Acyrthosiphon svalbardicum (Hemiptera: Aphididae) on Spitsbergen?

BackgroundThe Svalbard endemic aphid Acyrthosiphon svalbardicum (Heikinheimo, 1968) is host specific to Dryas octopetala L. ssp octopetala (Rosaceae). It has been hypothesized that the aphid is present on those areas with a thin winter snow cover and which therefore clear of snow earlier in the season. This early snow clearance results in a longer growing period and allows the aphid to experience at least the minimum number of degree days required to complete its life cycle. However, this hypothesis lacked a detailed field validation. We aimed to test the relationship between the aphid distribution and time of snow clearance at landscape scale, mapping snow depth at peak of snow accumulation for the two succeeding years 2009 and 2010 and examining site occupancy and plant phenology the following summers. Additionally, the distribution range mapped by Strathdee & Bale (1995) was revisited to address possible changes in range along the coast of the fjord.ResultsA linear relation between snow depth and timing of snow melt was found but with strong inter-annual and landscape variation. Both snow depth and plant phenology were found to affect patch occupancy. In August, the aphid, at the three life stages scored (viviparae, oviparae/males and eggs), was present most frequently in those D. octopetala patches with the most advanced plant phenology and which showed shallower snow depths in spring. However, many patches predicted to contain aphids were empty. The aphid distribution range has expanded 4.7 km towards the fjord mouth from 1995.ConclusionsSnow depth alone, and hence date of snow clearance, cannot precisely define species distribution at landscape scale, as this cannot explain why are they unoccupied patches under shallow snow depths with advanced plant phenology. We nonetheless present a model Arctic system that could form the basis for long term monitoring for climate- driven species shifts.