Winter Survival Research Articles

Switchgrass sward establishment selection is consistent across multiple environments and fertilization levels

AbstractBackgroundStrong selection can occur during switchgrass sward establishment. Differences in establishment selection due to environment or management could provide information on genotype‐by‐environment variation and could influence strategies for breeding perennial grasses.MethodsLeaf samples were collected before sward establishment and from 3‐year‐old swards for two breeding groups (lowland and hybrid) at three locations. Within two locations, samples were collected from paired fertilized (112 kg N ha−1) and unfertilized plots. Allele frequencies from pooled DNA samples were studied through multivariate analysis of variance, genomewide trait predictions (heading date and winter survivorship), and genomically estimated breeding values (GEBVs) for individual sward survival within an independent data set.ResultsThis study found only minor variations in selection due to location or management. Predicted heading dates of the hybrid population had significant changes due to fertilization and location. There were strong correlations among sward establishment survival GEBVs between growing environments (hybrid r = 0.77; gulf r = 0.97). Interestingly, this study found a small number of genotypes that were over‐represented in established swards across all growing environments.ConclusionsThis study reinforces a prior report of selection during sward establishment and indicates that only a small degree of establishment selection is location‐specific within these diverse growing conditions.

Weed hosts and winter survival of Stemphylium vesicarium on onion in Ontario, Canada

Stemphylium leaf blight (SLB), caused by the fungal pathogen Stemphylium vesicarium, is an important disease of onion (Allium cepa). This pathogen also causes disease on a wide range of other plant species. SLB on onion is managed primarily through fungicide application. The source of primary inoculum and whether S. vesicarium can overwinter in the region were not known. Inoculation and subsequent re-isolation of the pathogen from common weed species present near onion fields demonstrated that many of these weedy species are hosts of S. vesicarium. Redroot pigweed (Amaranthus retroflexus), yellow nutsedge (Cyperus esculentus), yellow marshcress (Rorippa palustris), perennial sow thistle (Sonchus arvensis) and purslane (Portulaca oleracea) were identified as new hosts of S. vesicarium and bull thistle (Cirsium vulgare) was confirmed as a host. Sporulation on dead weed residue in spring may be a source of primary inoculum for infection of adjacent onion fields. Also, a study of pathogen survival in infected leaf pieces of onion buried in soil or left at the soil surface demonstrated that S. vesicarium can overwinter in infected onion leaf residue and produce pseudothecia and ascospores in early spring. These conclusions support existing management recommendations for the burial or removal of onion debris and managing weeds in and around onion fields.

FER and LecRK show haplotype-dependent cold-responsiveness and mediate freezing tolerance in Lotus japonicus.

Many plant species have succeeded in colonizing a wide range of diverse climates through local adaptation, but the underlying molecular genetics remain obscure. We previously found that winter survival was a direct target of selection during colonization of Japan by the perennial legume Lotus japonicus and identified associated candidate genes. Here, we show that two of these, FERONIA-receptor like kinase (LjFER) and a S-receptor-like kinase gene (LjLecRK), are required for non-acclimated freezing tolerance and show haplotype-dependent cold-responsive expression. Our work suggests that recruiting a conserved growth regulator gene, FER, and a receptor-like kinase gene, LecRK, into the set of cold-responsive genes has contributed to freezing tolerance and local climate adaptation in L. japonicus, offering functional genetic insight into perennial herb evolution.

Evaluating risks associated with capture and handling of mule deer for individual‐based, long‐term research

AbstractCapture and handling techniques for individual‐based, long‐term research that tracks the life history of animals by recapturing the same individuals for several years has vastly improved study inferences and our understanding of animal ecology. Yet there are corresponding risks to study animals associated with physical trauma or capture myopathy that can occur during or following capture events. Rarely has empirical evidence existed to guide decisions associated with understanding the magnitude of capture‐related risks, how to reduce these risks when possible, and implications for mortality censoring and survival estimates. We used data collected from 2,399 capture events of mule deer (Odocoileus hemionus) via helicopter net‐gunning to compare daily survival probabilities within a 10‐week period centered on a capture event and evaluated how animal age, nutritional condition (body fat), and various handling methods influenced survival before, during, and following a capture event. Direct mortality resulting from capture efforts was 1.59%. Mean daily survival was 0.9993 ± 0.0001 (SE) during the 5‐week pre‐capture window, was depressed the day of capture at 0.9841 ± 0.0004, and rebounded to 0.9990 ± 0.0008 during the 5‐week post‐capture window. Neither capture nor handling had a detectable effect on post‐capture survival, including handling time ( = 13.30 ± 1.87 min), capture time of year (i.e., Dec or Mar), tooth extraction, and the number of times an animal had been recaptured (2–17 times). Although mortality rate was slightly elevated during capture (resulting from physical trauma associated with capture), age and nutritional condition did not influence the probability of mortality during a capture event. Following a capture event, nutritional condition influenced survival; however, that relationship was consistent with expected effects of nutritional condition on winter survival and independent of capture and handling. Overall survival rates 5 weeks before capture and 5 weeks after capture were not different. A specified window of time with depressed survival following capture and handling was not evident, which contradicts the implementation of a predetermined window often used by researchers and managers for censoring mortalities that occur after capture. Previous notions that censorship of all mortality data in the 2 weeks following capture is unwarranted and risks removal of meaningful data. With previous evidence guiding our protocols for capture (e.g., reduced chase time) and handling (e.g., temperature mitigation), low direct mortality and almost undetectable indirect mortality post capture reinforces the efficacy of helicopter net‐gunning for capture and recapture of mule deer in long‐term, individual‐based studies.

Behavior of snow monkeys hunting fish to survive winter

Japanese macaques, Macaca fuscata, of Kamikochi in the Japanese Alps endure one of the coldest and harshest environments during winter when scarcity of food puts them at risk. However, various behaviors have evolved to mitigate potential mortality. These macaques typically eat bamboo leaves and the bark of woody plants in winter, but our previous study using the feces of Japanese macaques collected in the winter and DNA metabarcoding analysis revealed conclusively for the first time consumption of riverine benthos and brown trout. In this paper, we investigate how Japanese macaques hunt fish and collect these riverine biota by extensively observing their behavior, including the use of infrared sensor cameras. Many researchers have tracked Japanese macaques as part of behavioral and ecological studies, but previously the techniques by which Japanese macaques capture swimming fish has not been documented. Herein, for the first time we consider how novel macaque foraging behavior traits have evolved to secure valuable animal protein for winter survival when food resources are scarce.

Registration of LCS ‘Valiant’ hard red winter wheat

AbstractHistorically cultivars developed jointly by the University of Nebraska‐Lincoln and USDA‐ARS wheat (Triticum aestivum L.) improvement project tend to be late and better adapted to the northern Great Plains. LCS ‘Valiant’ (Reg. no. CV‐1196, PI 693223; tested as NE10478‐1) was released based on the merits of its earliness, agronomic performance, relevant disease resistances, and end‐use quality characteristics and its adaptation to the central Great Plains. As such, the line was licensed to Limagrain Cereal Seeds for their ability to market outside of Nebraska. LCS Valiant hard red winter wheat was released in March 2020 by the developing institutions and the licensee. NE10478‐1 was a selection in 2011 for uniformity and grain yield from NE10478, which was derived from the cross NI03418/‘Camelot’. The pedigree of NI03418 is W91‐248/NE95544 (=McVey 78015/NE88521)//‘Thunderbird’. The final cross of NE10478 was made in 2004. The F1 generation was grown in Yuma, AZ, in 2005, and the F2 to F3 generations were advanced as bulks at Mead, NE, in 2006–2007 or sent for Hessian fly resistance screening by the USDA. In 2007, single F3‐derived F4 rows were planted for selection. There was no further selection in NE10478 other than to remove off‐types thereafter until 2011 when heads were selected to increase uniformity. LCS Valiant was evaluated in replicated trials thereafter. It has excellent winter survival, acceptable reactions to many of the common diseases in its target area, and good end‐use quality for bread making.

Genetic variability and QTL mapping of winter survivability and leaf firing in African bermudagrass

AbstractTurf‐type bermudagrass is susceptible to winterkill when grown in transition zone climates. Minimizing water use in turfgrass management is of societal significance. African bermudagrass (Cynodon transvaalensis Burtt‐Davy) has been extensively used to cross with common bermudagrass (C. dactylon Pers. var. dactylon) in the creation of F1 hybrid cultivars. Little information regarding the molecular basis of winter survivability and drought resistance in African bermudagrass is available. Accordingly, the objectives of this study were to quantify genetic variability and identify quantitative trait loci (QTL) associated with winter survivability traits (spring greenup, SG; spring greenup percent green cover, SGPGC; winterkill, WK), and leaf firing (LF) in African bermudagrass. A total of 109 first‐generation self‐pollinated (S1) progeny of ‘OKC1163’ were evaluated in a field trial in a randomized complete block design with three replications for four seasons. Significant genetic variation existed for all the traits examined, and the broad‐sense heritability estimates ranged from .36 to .54 for the winter survivability traits and .80 for LF. Ten QTL were identified for winter survivability traits and two for LF based on a preexisting high‐density linkage map, which was aligned, reoriented, and renamed as to a recently published reference genome. Seven of 12 QTL were consistently identified at least in 2 yr. The colocation of two QTL, one for winter survivability and another for LF, suggests the possibility of improving both traits together. Findings provide new insights to genetic control of winter survivability traits and LF and contribute genetic resources for marker‐assisted selection in turf‐type bermudagrass improvement.

Fire blight resistance, irrigation and conducive wet weather improve Erwinia amylovora winter survival in cankers.

Erwinia amylovora causes fire blight, a disease responsible for enormous economic losses in the pome fruit-producing areas where it is present. Despite the abundant research on fire blight, information about E. amylovora population dynamics and survival in fire blight cankers and the plant defense responses to this pathogen in the infected bark are limited. In our study, we obtained fire blight cankers in apple, pear, and Asian pear cultivars showing differing resistance to the disease by shoot inoculation with E. amylovora. We collected cankers from irrigated and non-irrigated trees every 3 months in two independent field experiments and analyzed samples by viability digital PCR. We also assessed the expression of pathogenicity-related (PR) genes in the bark of selected apple and Asian pear cultivars. A logistic regression analysis revealed the impact of environmental and host factors on E. amylovora detection rates in cankers. The chances of detecting live E. amylovora cells in cankers increased significantly in those collected from irrigated trees, in July, and/or during an experiment performed in a year with an expected average rainfall when compared to samples from non-irrigated trees, collected in January, and/or during an experiment performed under environmental conditions dominated by drought. We found a positive correlation between the pathogen detection rates in cankers and the host resistance to fire blight that might be explained by lower E. amylovora survival rates in more damaged tissues of susceptible hosts. The genes PR-1, PR-2, PR-5, and PR-8 were induced in the bark surrounding apple and Asian pear fire blight cankers. Our study, involving the analysis of more than 800 canker samples, provides new knowledge about the fire blight disease cycle and lays the foundation for improved fire blight management and eradication strategies in pome fruit orchards.

Substance accumulation of a wetland plant, Leersia japonica, during senescence in the Yihe and Shuhe River Basin, North China.

Leersia japonica is a perennial Gramineae grass that is dominant in shallow wetlands of the Yihe and Shuhe River Basin, North China. Previous studies have shown that L. japonica recovers early (March), tillers strongly, and has an excellent ability to purify sewage in spring. This early revival might play a vital role in water purification function; however, whether the plant benefits from the physiological activities during senescence remains unclear. Therefore, in this study, an experiment was conducted during the winter of 2016 and in the following spring. Morphology (height, biomass, root morphology), physiology (root vitality, malondialdehyde [MDA], superoxide dismutase [SOD]), substance contents (soluble sugar, soluble protein) and substance transportation (activity of enzymes for transportation and energy supply) were determined during weeks 0, 2, 4, 6, and 8 of the senescence stage (October 11, 2016); as well as substance contents and bud increments during days 0,7, 14, 21, 31 and 41 of the revival period (February 22, 2017). The results revealed that (1) the root biomass of L. japonica increased significantly during senescence, even after the leaves withered. (2) The root diameter of L. japonica decreased significantly, while root weight per volume and root superficial area per volume increased significantly during senescence. The root vitality was relatively stable in winter, especially for root absorption area per volume. (3) No significant difference was observed in membrane stability of stems, rhizomes and roots of L. japonica in winter, with the MDA content remaining stable and SOD activity increasing significantly during senescence. (4) The soluble sugar content of all tissues of L. japonica increased sharply during senescence; while it decreased significantly in spring, especially for buds. (5) The enzymes for substance metabolism responded differently, with activities of H+-ATPase and pyruvate decarboxylase (PDC) decreasing, and alcohol dehydrogenase (ADH) increasing. Therefore, L. japonica has active morphological adaptation of roots, physiological regulation, and massive substance accumulation during senescence stage. The special life-history trait ensures L. japonica survival in winter and revival in early spring, which makes it being an excellent plant for purifying sewage in spring.

Improving winter barley adaptation to freezing and heat stresses in the U.S. Midwest: bottlenecks and opportunities

Continental cropping systems are increasingly exposed to extreme and opposing trends of temperatures over the same growing season. This situation is epitomized by winter barley grown in the Upper Midwest, which is subject to temperatures that can be as low as −30 °C during the winter and over 30 °C during summer. This interaction severely limits the potential of this emerging crop, by threatening the winter survival of the crown which is often exposed to lethal freezing stress and by exposing reproductive organs to high temperature (HT) stress, to which this cool-season grass is highly sensitive. This poses a unique challenge that requires the discovery and capture of well-defined sets of traits enabling adaptation to extreme tail ends of a stressor, with limited trade-offs, while minimizing costs. Here, based on a critical literature review, we propose a framework integrating i) environmental characterization (envirotyping), ii) envirotype-relevant scouting of genetic resources, iii) ecophysiology-informed trait identification and phenotyping and iv) breeding pipelines. We outline propositions and guidelines for implementing these steps and discuss their feasibility, with an emphasis on i) identifying novel genetic resources and eco-physiological traits relevant to this problem, ii) navigating their physiological trade-offs and iii) leveraging this information to develop ad hoc phenotyping methods for deployment in breeding programs. Our review indicates that the eco-physiological and genetic bases for improving tolerance to both stresses in the same organism likely exists based on evidence from crop relatives and extremophile species, with smaller vasculature (freezing tolerance) and transpirational cooling (HT tolerance) being prime examples. Our findings indicate that such traits could be captured with minimal trade-offs, and that is possible to use similar phenotyping concepts (thermal imaging) and infrastructure (cold/heat tents) to screen for these traits and accelerate breeding to enhance adaptation to temperature extremes. • Temperature extremes limit winter barley yields grown in the Upper Midwest. • Freezing stress limits crown survival and heat stress limits reproductive development. • A trans-disciplinary framework is proposed to improve adaptation to both stressors. • Physiological/ genetic bases for adaptation to both stresses likely exists. • Possibility to use similar phenotyping infrastructure for promising traits.

Promising cultivars of winter triticale for grain production in the north-west of the Astrakhan region

Triticale, due to its specific properties to form stable grain yields in the zones with risky agriculture, should find wider application in acutely arid conditions. Therefore, the use of highly productive cultivars of winter triticale in semi-desert zone of the north-west of the Astrakhan region is relevant. The aim of the research was a comprehensive assessment of promising winter triticale cultivars of different ecological and geographical origin for adaptability to stressful meteorological factors in semi-desert zone of the northwestern Astrakhan region. To determine the main indicators of adaptability (winter hardiness, plasticity, stability, stress tolerance, genetic flexibility), six promising winter triticale cultivars (Tribun, Interes, PRAG 152, Khleborob, Zhnets and Uragan) were studied. Field agroecological tests were conducted on rainfed fields of Precaspian Agrarian Federal Scientific Center of the RAS with different moisture level in 2018-2020. Nelli cultivar was used as a control. The methods of Selyaninov G.T., Zhivotkov L.A., Eberhart S.A., and Rassell W.A. were used for calculations. During periods of active vegetation of winter triticale, Selyaninov hydrothermal coefficient varied from 0.3 to 0.5 (zone of strong and very strong drought); environment index was from -0.67 to 0.66. According to the data obtained, cv. Khleborob showed the greatest adaptive potential and consistently high yield under various meteorological conditions of the season compared to the other tested winter triticale varieties. Moreover, the cultivar had good winter hardiness (5 points) and survival (90.8 %). On the average for the years of research it showed high adaptability coefficient (1.43), and the indicators of its plasticity and genetic flexibility were 0.77 and 1.40, respectively. Therefore, cv. Khleborob can be recommended for use in the acutely arid conditions in semi-desert zone of the northwestern part of the Astrakhan region.

The effects of temperature extremes on survival in two semi‐arid Australian bird communities over three decades, with predictions to 2104

AbstractAimOrganisms in arid and semi‐arid regions are frequently exposed to climatic extremes and accordingly among the most vulnerable to climate change. Studies of seasonal differences in vital rates, which mediate effects of climate on viability, are rare in arid species, limiting ability to project population trends. We quantified survival patterns for two bird communities as a function of exposure to temperature extremes in winter and summer, then projected survival patterns to 2104.LocationSemi‐arid eastern Australia.Time period1986–2016; 1986–2104.Major taxa studiedBirds.MethodsUsing mark–recapture time‐dependent Cormack–Jolly–Seber models and data for 37 species from two >30‐year ringing programmes, we tested for effects on 6‐monthly survival of exposure to temperatures >38 and <0°C. We then predicted future survival for different emission scenarios, testing whether changes in survival associated with warming winters would be sufficient to offset the effects of rising summer temperatures.ResultsSurvival probability declined strongly with increasing exposure to days >38°C and to a lesser extent to days <0°C, with temperature extremes explaining 43 and 13% of temporal variation in survival among years, respectively. Summer survival patterns were similar across avian guilds but only survival of nectarivores declined in winter. Our models predict that gains in winter survival will not offset reductions in summer survival. Annual survival is predicted to decline substantially by the end of the century: from .63 in 1986 to .43 in 2104 under an optimistic emission scenario and to .11 under a pessimistic scenario.Main conclusionsWe highlight the significance of temperature extremes for species' persistence in arid and semi‐arid regions, comprising 70% of Australia's landmass, and 40% globally. Our demography‐based results are consistent with physiological‐based projections evaluating avian survival in arid and semi‐arid regions globally and suggest rising summer temperatures pose a risk to population persistence in these regions.

Effects of Hibernation Site, Temperature, and Humidity on the Abundance and Survival of Overwintering Culex pipiens pipiens and Anopheles messeae (Diptera: Culicidae).

Knowledge of the hibernation site preferences and the factors which influence winter survival in these hibernation sites may enhance understanding of mosquito population dynamics after winter and how arboviruses persist in temperate regions. Our study quantified the number of adult overwintering mosquitoes in cellars and aboveground constructions and analyzed survival rates in relation to the environmental conditions in these sites. During the winters 2016/2017 and 2018/2019, 149 different constructions in Northwest Germany were sampled for mosquitoes. Mosquitoes were detected in 44% of the cellars and in 33% of the aboveground constructions. Culex p. pipiens Linnaeus was the most abundant species in cellars, whereas high numbers of Anopheles messeae Falleroni were collected from a single barn. Subsequently, an enclosure study was conducted during 2019/2020. Overwintering field-collected Cx. p. pipiens and An. messeae were divided into groups with or without fructose availability, and placed in cages with different man-made hibernations sites, where temperature and relative humidity were recorded hourly. For both species, increasing mean temperatures (5-16°C) but not mean relative humidity (58-94%) were correlated with winter mortality rates of the mosquitoes. The lipid measurements were greater and mortality rates were lower when both species were provided fructose. Larger specimens (determined by wing length) stored more lipids, and in Cx. p pipiens, but not in An. messeae, survival probability of large specimens was significantly greater than for small females. Mosquitoes showed a distinct pattern in the selection of overwintering sites, while temperature was an important driver for survival.

Energy Consumption and Cold Hardiness of Diapausing Fall Webworm Pupae.

Simple SummaryThe fall webworm, Hyphantria cunea, a major invasive pest in China, overwinters as diapausing pupae, but seasonal changes in energy consumption and cold hardiness of diapausing pupae are still unclear. In this study, we investigated the seasonal variation in lipid, glycogen, and trehalose content accompanying changes in the supercooling points of diapausing pupae. We found that the energy consumption of H. cunea diapausing pupae was dominated by lipid and carbohydrates early in diapause and shifted to glycogen or other energy stores as diapause progressed. We also found that an increase in pupal diapause development time had a significant negative effect on the survival rate of pupae during diapause and the post diapause adult fitness. This information is essential for the development of a theoretical foundation to better understand the overwintering strategy of H. cunea and for improving forecasts of the population dynamics according to the thermal conditions in various years.Diapause and cold hardiness are essential components of winter survival for most insects in temperate zones. The fall webworm, Hyphantria cunea, overwinters in a pupal diapause. In this study, we investigated the energy consumption and cold hardiness of diapausing pupae. We found that lipid content decreased from October to November and stabilized from November to March. Glycogen content decreased by 61.3% and 52.2% for females and males, respectively, from October to November, and decreased slowly from November to March. We also observed a significant increase in trehalose concentrations as ambient temperatures decreased from October to November and a decrease in trehalose as temperatures increased again in March. We did not observe substantial changes in pupal supercooling points among the dates sampled. In addition, prolonged pupal development time reduced their survival rate and had no significant effect on post-diapause adult body mass and fecundity but reduced egg diameter in females. These results suggest that the energy consumption of H. cunea pupae during early diapause depends on lipid and glycogen, while it shifts to depend on glycogen or other energy stores in the mid- and late diapause stages. Our results also suggest that the prolonged development time of diapausing pupae had a negative effect on post-diapause fitness.

Status of the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) pathway in liver and skin of the freeze tolerant wood frog

The wood frog (Rana sylvatica) has adapted full-body freezing and thawing as a means of sub-zero winter survival and early-breeding in ephemeral pools. One such protective process implicated recently in freeze-thaw tolerance is that of anti-apoptotic signaling, which has been proposed to play a cytoprotective role by modulating stress-induced death signals. This study employed the use of immunoblotting to examine response of a potent cell cycle and apoptosis regulator, known as the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway, to freezing and thawing in the liver and skin of the wood frog. This pathway demonstrably exhibits factor- and tissue-specific changes between non-frozen, 24 h-frozen, and 8 h-thawed conditions. There were few changes in JAK-STAT proteins in frozen frogs, but protective changes were observed upon thaw: Elevated levels of pJAK3 and nuclear localization of pSTAT3 and pSTAT5 suggested an increase in anti-apoptotic signaling after thaw. By contrast, both STAT1 and STAT3 signaling appeared to increase in frozen skin, suggesting frogs use homeostatic regulation of apoptotic- and anti-apoptotic signals, in an antagonistic and compensatory manner. As such, these findings support that JAK-STAT pathway signaling modulation is a plausible adaptation that contributes to fast and reversible manipulation of anti-apoptotic signals, thus assisting in freeze survival of the wood frog.

The role of temperature on overwinter survival, condition metrics and lipid loss in juvenile polar cod (Boreogadus saida): A laboratory experiment

In the Arctic, winter warming and loss of sea ice pose largely unknown risks to keystone species and the marine ecosystem that they support. Young-of-the-year juvenile polar cod, Boreogadus saida, are an energy-rich forage fish that accumulate high levels of lipid in the summer but retain a relatively small body size during the winter. To address winter bioenergetics and survival, we held age-0 juveniles under simulated winter conditions (food deprived, 24-hr darkness) at a range of four constant temperatures (−1, 1, 3, 5 °C). Our goals were to 1) determine how age-0 polar cod utilize lipid energy in muscle and liver across variable temperatures and durations of food deprivation, 2) understand temperature- and size-dependent impacts on survival and 3) provide energy loss models using multiple condition metrics that are commonly used in fisheries science (lipids, morphometric ratios, body weight). These data have relevance to projecting winter outcomes for polar cod sampled pre-winter, when fish are more easily sampled in the field. As expected, in the absence of food, juvenile polar cod better conserved lipids and survived longer at colder temperatures. There was no negative impact of cold extremes on this pattern; for example, 50% mortality was at 170 days when polar cod were held at −1 °C, compared to only 94 days when they were held at 5 °C. During the first 28 days of simulated winter, polar cod preferentially catabolized triacylglycerols from muscle tissue, then depleted this storage lipid class in their muscle and liver until starvation. Mortality occurred when whole-body lipid concentrations fell below 12.4 mg g−1 wet weight. Temperature-dependent declines in morphometric condition (hepatosomatic index and Fulton's K) and lipid content were parameterized and developed into temperature-dependent condition loss models. Applying a laboratory-based lipid loss model to field-collected polar cod demonstrated that winter survival is highly sensitive to small changes in temperature between −1 and 1 °C when fish are in good condition at the end of the preceding summer. Alternatively, fish in poor summer condition cannot survive winter relying exclusively on stored energy reserves, and will be required to forage throughout the winter. Collectively, these results suggest that lipid-based indices offer a sensitive means of predicting overwintering success for polar cod experiencing climate-driven changes in summer and winter habitats in the Arctic.

Resistance of Almond (Prunus dulcis) to Xylella fastidiosa: A Comparative Study on Cultivars

Almond leaf scorch is a disease caused by Xylella fastidiosa, which is increasingly widespread globally in the main almond cultivation areas. Previously confined to America, in the last decade this disease has been reported in Iran and southern Europe. In this comparative study, the resistance to X. fastidiosa subsp. multiplex of 13 almond cultivars (Mamaei, Non-Pareil, Sefied, Rabie, Ferragnes, Shahrood21, Thompson, Merced, Marcona, Frudeul, Kapariel, Princess, and Tuono) grafted onto seedlings of Talkhe was evaluated in controlled conditions. Plants were artificially inoculated and maintained in greenhouse conditions. Approximately 3 months after inoculation, three times at 3-week intervals, disease incidence, disease severity, and disease index were determined based on scaling, and bacterial populations were estimated. The effect of winter survival of bacteria in outdoor potted seedlings was also investigated in all almond cultivars. Findings showed a great degree of variability in response to X. fastidiosa among cultivars considering symptom development and severity, as well as bacterial titer. Thompson and Rabie cultivars scored the best results from both a symptomatological and infectious point of view, indicating resistance against the pathogen compared with other tolerant cultivars (e.g., Ferragnes, Tuono, and Kapariel), thanks to the development of mild symptoms. Mamaei, Non-Pareil, and Sefied scored worst, suggesting a susceptible behavior when infected by X. fastidiosa. Given that the pathogen was not detected by culturing and PCR during the following summer, bacterial population in potted seedlings was reduced significantly by overwintering in outdoor conditions regardless of cultivar susceptibility. This suggests that cold treatment can be used as a preventive treatment to manage nursery almond seedlings.

Temporal and Spatial Positioning of Service Crops in Cereals Affects Yield and Weed Control

Leguminous service crops (SCs) can provide multiple services to cropping systems, reducing the reliance on external resources if sufficient biomass is produced. However, rapid light and temperature reductions limit post-harvest cultivation of SCs in Northern Europe. A novel practice of intercropping SCs in two consecutive crops (spring–winter cereal) to extend the period of SCs growth, and hence improve yield and reduce weeds, was tested. Three spatial and temporal arrangements of SCs and cash crops were investigated, as well as three SC mixtures, characterized by their longevity and frost sensitivity. Compared to no SC, the best performing mixture, frost-tolerant annuals, increased grain and N yield of winter wheat by 10% and 19%, respectively, and reduced weed biomass by 15% and 26% in oats and winter wheat, respectively. These effects were attributed to high biomass production and winter survival. However, this SC reduced oat yields by 15% compared to no SC. Furthermore, SC growth and service provision varied largely between experiments, driven by the weather conditions. Extending the SC’s growth period by intercropping in two consecutive cereal crops has potential, but locally adapted species choices and establishment strategies are needed to ensure SC vitality until termination.

Effectiveness of electric harps in reducing Vespa velutina predation pressure and consequences for honey bee colony development.

Vespa velutina has become a species of concern in invaded regions of Europe and Asia, due to its impacts on biodiversity, apiculture and society. This hornet, a ferocious hunter of pollinating insects, poses a serious threat to biodiversity and pollination services. Despite ongoing efforts, its extermination in continental Europe is hampered by a lack of effective control methods, thus effective mitigation measures are primary concerns. The aims of this work were: (i) to study the effects of V. velutina predating on honey bee colonies, and (ii) to assess the effectiveness of electric harps in reducing hunting pressure and predation. We assessed the predation pressure and compared honey bee colony performance, body weight of workers, and winter survivorship for protected versus unprotected colonies in 36 experimental hives across three apiaries. Electric harps protected honey bees by reducing predation pressure and therefore mitigating foraging paralysis. Consequently, foraging activity, pollen income, brood production and worker body weight were higher in protected colonies which in turn showed greater winter survivorship than those that were unprotected, especially at sites with intermediate to high levels of predation. The predation of V. velutina affects foraging activity, breeding, body weight and colony survivorship of Apis mellifera. Electric harps contribute significantly to mitigate the impact of this invasive hornet on apiaries; however, they should be deployed in tandem with additional measures to preserve honey bee colony stocks, such as facilitating access to food sources for colonies during the periods of highest predation pressure. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Role of weather and other factors in the dynamics of a low-density insect population.

Insect population dynamics are the result of an interplay between intrinsic factors such as density dependence, trophic web interactions, and external forces such as weather conditions. We investigate potential mechanisms of population dynamics in a natural, low‐density insect population. Eggs and larvae of the noctuid moth, Abrostola asclepiadis, develop on its host plant during summer. The population density, and mortality, was closely monitored throughout this period during 15 years. Densities fluctuated between one and two orders of magnitude. Egg–larval developmental time varied substantially among years, with lower survival in cool summers with slower development. This was presumably due to the prolonged exposure to a large guild of polyphagous arthropod enemies. We also found a density‐dependent component during this period that could be a result of intraspecific competition for food among the last larval instars. Dynamics during the long period from pupation in late summer through winter survival in the ground to adult emergence and oviposition the next year displayed few clear patterns and more unexplained variability, thus giving a more random appearance. The population hence shows more unexplained or unpredictable variation during the long wintering period, but seems more predictable over the summer egg–larval period. Our study illustrates how weather—via a window of exposure to enemies and in combination with density‐dependent processes—can determine the course of population change through the insect life cycle.