Understanding the population dynamics of a rare, polyvoltine butterfly

Understanding the effects of endogenous and exogenous factors on population dynamics is essential for assessing the viability of populations, setting recovery goals for endangered species, and evaluating management options. Invertebrates are particularly difficult to monitor and few long-term datasets are available for these species. Additionally, limited resources make it necessary to perform monitoring as efficiently as possible. Here, I use the bivoltine Karner blue butterfly Lycaeides melissa samuelis to demonstrate how analyzing the effects of density-dependent factors and weather on separate life stages can be utilized to understand monitoring data, assess populations and identify critical life-history parameters. My first step was to compare the use of peak numbers as an index of population size with estimates obtained from a more data intensive methodology. Peak numbers proved to be an effective index, and so I utilized this index to analyze 10 and 13 years of monitoring data at two Karner blue butterfly sites in New York, USA. I modeled the effects of weather and density dependence on two distinct population growth rates ( λ ) per year. Analysis with Akaike's Information Criteria indicated that both sites were primarily influenced by density dependence during the summer period and by weather conditions during the winter period. Large population declines occurred in the winter period and were a result of the previous year's dry summer and cool spring weather. I conclude that recovery goals for this endangered species should include a second brood-carrying capacity, mean winter growth rate and multiple sites with independent populations. This study represents a rare, long-term study on the population dynamics of a polyvoltine species. Understanding the population dynamics of polyvoltine species, such as the Karner blue butterfly, will assist in the conservation of many invertebrate and small mammal species.     

Response of calcareous grassland vegetation to mowing and fluctuating weather conditions

Question: What determines the balance between the cover values of vascular plants, lichens and mosses in dry calcareous grassland communities? Location: Western Estonia. Methods: A five‐year (2001–2005) study was conducted in a dry calcareous grassland. The cover of mosses, lichens and vascular plants and all moss species was recorded in permanent plots. Vascular plants were cut in half of the plots. Data from a nearby weather station were used to calculate mean values of different weather parameters and a summer moisture index for the study years. Results: Significant differences in cover values between years were found. The fluctuations of total moss cover and the cover of the dominating moss species Ctenidium molluscum followed changes in annual precipitation. Both cover values were highest in years with high precipitation. The cover change of vascular plants was best characterized by the moisture index of the growth period (three summer months). Summers with high moisture indexes facilitated vascular plant and lichen growth. Annual precipitation and the cover of mosses had a negative influence on the cover of vascular plants. The cutting of vascular plants did not have a significant effect on moss and lichen cover. Conclusions: 1. On dry calcareous grasslands the growth of mosses is enhanced by high annual precipitation, while the growth of vascular plants and lichens is influenced rather by the high summer moisture index. The cover of vascular plants is inhibited by the large moss cover. 2. Mowing of vascular plants does not influence the cover of mosses and lichens.     

A climate index and mule deer fawn survival in Montana

A sign of deviation type of index was used to convert standard temperature and precipitation data into a readily used form for the study of deer population dynamics. Statistically significant correlations between the climate index and mule deer fawn survival were demonstrated for four different mule deer populations in Montana. These correlations led to reasonable biological hypotheses delineating the linkage between climate and fawn survival in each of the four areas. The correlations support the frequent observations in the wildlife literature concerning the importance of summer and winter range. They also suggest that human activities may interact with climate in a manner which affects deer fawn survival. In general, in these areas, fawn survival was favored by relatively warm-moist summer, warm-dry winter and cool-dry hunting season weather. The apparent affect of spring weather was variable. Fawn survival in two areas was enhanced by cool-dry summer weather. This reversed response could be the result of human use of the areas, including livestock grazing. It is concluded that this index of climatic fluctuations can be a versatile and useful tool in assessing the impact of climate upon deer populations. In general, weather can be described as a strong biasing factor even when direct effects cannot be consistently demonstrated.     

Biometeorological and autoregressive indices for predicting olive pollen intensity

This paper reports on modelling to predict airborne olive pollen season severity, expressed as a pollen index (PI), in Córdoba province (southern Spain) several weeks prior to the pollen season start. Using a 29-year database (1982–2010), a multivariate regression model based on five indices—the index-based model—was built to enhance the efficacy of prediction models. Four of the indices used were biometeorological indices: thermal index, pre-flowering hydric index, dormancy hydric index and summer index; the fifth was an autoregressive cyclicity index based on pollen data from previous years. The extreme weather events characteristic of the Mediterranean climate were also taken into account by applying different adjustment criteria. The results obtained with this model were compared with those yielded by a traditional meteorological-based model built using multivariate regression analysis of simple meteorological-related variables. The performance of the models (confidence intervals, significance levels and standard errors) was compared, and they were also validated using the bootstrap method. The index-based model built on biometeorological and cyclicity indices was found to perform better for olive pollen forecasting purposes than the traditional meteorological-based model.     

Climate change may account for the decline in British ring ouzels Turdus torquatus

1. Climate change is already affecting biodiversity, but the number of species for which reliable models relate weather and climate to demographic parameters is low. 2. We modelled the effect of temperature and rainfall on the breeding success and territory occupancy of ring ouzels Turdus torquatus (L.) in northern Britain, using data from a range of study areas, including one where there was a long-term decline in ring ouzel abundance. 3. Timing of breeding was significantly related to meteorological variables affecting birds in the early spring, though there was no evidence that laying dates had advanced. Breeding success was not significantly related to weather variables; instead, over 90% of annual variation in this parameter could be explained by density dependence. 4. Annual change in territory occupancy was linked to rainfall and temperature the preceding summer, after the main breeding season and to rainfall in the wintering grounds 24 months previously, coincident with the period of juniper Juniperus sp. (L.) flowering. High temperature in late summer, intermediate levels of late summer rainfall, and high spring rainfall in Morocco 24 months previously all had negative impacts on territory occupancy the following year. 5. All three weather variables have changed over recent decades, with a significant increase in summer temperature, a significant decrease in summer rainfall, and a nonsignificant decline in Moroccan spring rainfall. A model based on these trends alone predicted an annual decline in occupancy of 3.6% (compared with an observed decline of 1.2%), and suggested that increased summer temperatures may underlie declines in the British ring ouzel population. 6. Changes in summer temperature after the main breeding period could affect the survival rates of adult and/or juvenile birds. An improved understanding of the post-breeding ecology of ring ouzels is required to elucidate the mechanisms and causes of this relationship. Such knowledge might allow management aimed at buffering the impacts of climate change on ring ouzels.     

Weather conditions during hunting season affect the number of harvested roe deer (Capreolus capreolus)

Due to human‐induced climate and landscape changes, distribution and abundance of many ungulate species have increased worldwide. Especially in areas where natural predators are absent, hunting is the essential management tool for regulating ungulate populations. Therefore, understanding the factors associated with harvest rates is the first step toward an adaptive management approach. Weather influences hunter and ungulate behavior and thus presumably harvest, but how and which meteorological parameters are linked to harvest numbers have rarely been evaluated. We used nearly 65,000 “sit and wait” and driven hunt harvests of roe deer (Capreolus capreolus) in Bavaria, Germany, and weather data from 2008 to 2017 to test for factors affecting roe deer harvests (i.e., temperature, rain hours, wind speed, sunshine duration, snow depth, workdays vs. weekends, month) using zero‐inflated negative binomial mixed‐effect models. Our results reveal that, besides workdays, high temperatures and prolonged rain resulted in fewer harvested animals, whereas sunshine duration in summer and snow height in snow‐rich areas partially favored harvests during sitting hunts in summer and winter, respectively. The influence of wind speed varied over the course of the year. In summer and autumn, wind speed commonly had a negative effect, positively affecting harvests in winter in some regions. Daily harvest numbers decreased during the summer and autumn hunting periods (May till mid‐October), while they increased during the winter period (mid‐October till mid‐January). Interestingly, harvest success during driven hunts, which are planned well in advance and therefore take place largely independent of weather conditions, was similarly affected by the weather. This result suggests that the inferred weather influence is not only due to the hunters'' decisions but also due to deer behavior. Since many ungulate populations may further benefit from climate change, building an understanding of the relationship between hunting success and weather will aid adaptive ungulate management.     

Stronger Short-Term Effects of Mowing Than Extreme Summer Weather on a Subalpine Grassland

Mowing is known to favor plant diversity and influence ecosystem functioning in semi-natural grasslands. This effect could be influenced by climate variability, especially in regions with harsh climate, such as subalpine zones. In particular, short-term extreme weather fluctuations may induce rapid plant responses, affecting in turn the response to mowing. We tested the effects of concomitant summer weather manipulation and mowing on a subalpine grassland in the Central French Alps for two consecutive years. We addressed two questions: (1) How is a subalpine grassland affected by extreme summer weather? (2) Does extreme summer weather alter mowing effects on the grassland plant diversity and functioning? We used a multi-level, integrative approach assessing the responses of six abundant plant species, as well as effects on plant community structure, biomass production, and litter decomposition rates. Extreme summer weather was simulated by increasing summer temperature by 1.1°C, and decreasing summer rainfall by 80%—resulting in a 30% decrease in total annual precipitation. In addition, a heat-wave event was simulated during the first year of the experiment. This weather manipulation was combined with a late-summer mowing treatment (mown vs. unmown). Extreme summer weather mainly increased leaf senescence and decreased plant vegetative growth. Leaf litter decomposition was slowed, but only for species characterized by the fastest rates of litter decomposition. Mowing increased plant diversity by restricting the dominant grass species, thereby favoring subordinates. In the short term, this subalpine grassland was rather resistant to extreme summer weather, whereas mowing cessation remained the main factor affecting its biodiversity.     

Interannual variability of pollen productivity and transport in mid-North America from 1997 to 2009

Understanding the causes of interannual variability in atmospheric pollen concentration is an important but elusive goal for public health and environmental change. We analyzed long-term daily records of pollen counts from urban Kansas City, Missouri, USA collected from 1997 to 2009 for three pollen groups: Ambrosia, Poaceae, and a third group which is mostly composed of arboreal pollen types. The annual pollen index varied from 8,368 to 80,822 over the thirteen-year period. Although Ambrosia pollen is often thought to be associated with droughts and disturbance, years with high Ambrosia pollen were associated with high summer precipitation to the south of Kansas City. Years with high Poaceae pollen were associated with high spring precipitation to the south of the city. In support of the southern influence to Kansas City pollen, Ambrosia and Poaceae pollen mostly arrived on southern winds. In contrast to the other two pollen groups, the arboreal pollen was most associated with growing season precipitation to the east of Kansas City, although it was still highest on days with southern winds. Based on the correlations with climate, the severity of an upcoming allergy season may be predicted with early-season precipitation data, while short-term severity can be forecast from local weather patterns.     

Estimation of the tourism climate in the Hunter Region,Australia, in the early twenty-first century

Existing tourism-related climate information and evaluation are typically based on mean monthly conditions of air temperature and precipitation and do not include thermal perception and other climate parameters relevant for tourists. Here, we quantify climate based on the climate facets relevant to tourism (thermal, physical, aesthetical), and apply the results to the Climate-Tourism-Information-Scheme (CTIS). This paper presents bioclimatic and tourism climatological conditions in the Hunter Region—one of Australia’s most popular tourist destinations. In the Hunter Region, generally, temperatures below 15°C occur from April through October, temperatures less than 25°C are expected throughout the whole year, while humidity sits around 50%. As expected, large differences between air temperature and physiologically equivalent temperature (PET) were clearly identified. The widest differences were seen in summer time rather than in the winter period. In addition, cold stress was observed less than 10% of the time in winter while around 40–60% of heat stress was observed in summer time. This correlates with the highest numbers of international visitors, who usually seek a warmer weather, at the beginning of summer time (November and December) and also to the number of domestic visitors, who tend to seek cooler places for recreation and leisure, in late summer (January–March). It was concluded that thermal bioclimate assessment such as PET and CTIS can be applied in the Hunter region, and that local governments and the tourism industry should take an integrated approach to providing more relevant weather and climate information for both domestic and international tourists in the near future.     

Physical modelling of globe and natural wet bulb temperatures to predict WBGT heat stress index in outdoor environments

The present paper describes a physical model that estimates the globe and the natural wet bulb temperatures from the main parameters generally recorded at meteorological weather stations, in order to predict the wet bulb globe temperature (WBGT) heat stress index for outdoor environments. The model is supported by a thermal analysis of the globe and the natural wet bulb temperature sensors. The results of simultaneous measurements of the WBGT and climatological parameters (solar radiation, wind velocity, humidity, etc.) are presented and used to validate the model. The final comparison between calculated and measured values shows a good agreement with the experimental data, with a maximum absolute deviation of 2.8% for the globe temperature and 2.6% for the natural wet bulb temperature and the WBGT index. The model is applied to the design reference year for Coimbra, Portugal, in order to illustrate its preventative capabilities from a practical point of view. The results clearly show that during the summer there is a critical daily period (1200–1600 hours, local standard time) during which people working outdoors should not be allowed to perform their normal activities.     

Are badgers ‘Under The Weather’? Direct and indirect impacts of climate variation on European badger (Meles meles) population dynamics

Weather conditions, and how they in turn define and characterize regional climatic conditions, are a primary limit on global species diversity and distribution, and increasing variability in global and regional climates have significant implications for species and habitat conservation. A Capture–Mark–Recapture study revealed that badger (Meles meles) life history parameters interact in complicated ways with annual variability in the seasonality of temperature and rainfall, both in absolute and in phenological terms. A strong predictive relationship was observed between survival and both temperature and late‐summer rainfall. This link at the population dynamics level was related to individual body‐weight increases observed between summer and autumn. In addition, fecundity was correlated with spring rainfall and temperature. We investigated and confirmed that relationships were consistent with observed variation in the intensity of a parasitic infection. Finally, fecundity during any given year correlated with conditions in the preceding autumn. Badger survival also correlated with late winter weather conditions. This period is critical for badgers insofar as it coincides with their peak involvement in road traffic accidents (RTAs). RTA rate during this period was linked strongly to temperature, underlining the intricate ways in which a changing climate might interact with anthropogenic agents to influence species' population processes. Equinoctial conditions produced significant population driver effects. That is, while summers will always be relatively warm compared with winters, spring and autumn weather can be more variable and functionally delimit the ‘productive’ vs. nonproductive period of the year in terms of badger behavioural and physiological cycles. This study highlights how appropriately informed conservation strategies, mindful of trends in climatic conditions, will become ever‐more essential to ensure the survival of many species globally.     

Texas,Oklahoma and Kansas winter temperatures and rainfall,and summer occurrence ofPuccinia graminis tritici in Kansas,Dakotas, Nebraska,and Minnesota

Temperature and rainfall data for the winter months December through March in Texas, Oklahoma, and Kansas were related to subsequent summer wheat stem rust severity in Kansas, Nebraska, the Dakotas and Minnesota for the period 1904–1960.Kansas winter temperatures and rainfall data were not related to rust severity in the states northward.Although precise weather rules for rust epiphytotics were not found,these preliminary analyses indicated that there might be a causal relation between March precipitation in Texas and Oklahoma and subsequent wheat stem rust outbreaks in May in Kansas and June and July in Nebraska, the Dakotas and Minnesota.     

Effect of trophic status of a deep-water lake on breeding Great Crested Grebes Podiceps cristatus during a phase of recovery from eutrophication: a long-term study

Capsule: Trophic status of a deep-water lake was the main driver of changes in breeding population size of Great Crested Grebes Podiceps cristatus while reproductive success was also strongly affected by weather parameters.

Aims: To determine the effects of changes in nutrient status of a formerly highly-eutrophicated deep-water lake and other environmental parameters on a Great Crested Grebe population during a phase of re-oligotrophication.

Methods: Annual surveys were carried out on a natural lake in Switzerland over a period of 25 years to determine breeding population size and reproductive success. The effects of phosphorus content, other limnological parameters and weather variables were analysed with quasi-Poisson models.

Results: The breeding population increased from 80 pairs in 1992 to 417 pairs in 2001, after which numbers showed strong fluctuations. Total phosphorus content in the lake had a strong negative effect on breeding population size. A significant positive correlation was found with the national population index. Reproductive success fluctuated strongly but showed an overall decline. The model indicated positive effects on reproductive success of phosphorus and negative effects of the number of days with strong wind. Rapid water-level increases in early summer and water transparency in June led to higher proportions of late broods.

Conclusion: Phosphorus concentration was identified as the main driver affecting the breeding population of Great Crested Grebes during the phase of recovery of the lake from a highly-eutrophic state. Results indicate that mesotrophic to eutrophic conditions enabled a large population and high breeding success. Reproductive output was further negatively affected by strong wind during a critical breeding phase.     

Climatic change and fire potential in South-Central British Columbia, Canada

The incidence and severity of forest fires are linked to the interaction between climate, fuel and topography. Increased warming and drying in the future is expected to have a significant impact on the risk of forest fire occurrence. An increase in fire risk is linked to the synchronous relationship between climate and fuel moisture conditions. A warmer, drier climate will lead to drier forest fuels that will in turn increase the chance of successful fire ignition and propagation. This interaction will increase the severity of fire weather, which, in turn, will increase the risk of extreme fire behaviour. A warmer climate will also extend fire season length, which will increase the likelihood of fires occurring over a greater proportion of the year. In this study of the North Okanagan area of British Columbia, Canada, the impacts of climate change of fire potential were evaluated using the Canadian Forest Fire Danger Rating System and multiple climate scenario analysis. Utilizing this approach, a 30% increase in fire season length was modelled to occur by 2070. In addition, statistically significant increases in fire severity and fire behaviour were also modelled. Fire weather severity was predicted to increase by 95% during the summer months by 2070 while fire behaviour was predicted to shift from surface fire‐intermittent crown fire regimes to a predominantly intermittent‐full crown fire regime by 2070 onwards. An increase in fire season length, fire weather severity and fire behaviour will increase the costs of fire suppression and the risk of property and resource loss while limiting human‐use within vulnerable forest landscapes. An increase in fire weather severity and fire behaviour over a greater proportion of the season will increase the risks faced by ecosystems and biodiversity to climatic change and increase the costs and difficulty of achieving sustainable forest management.     

Tawny Owl Strix aluco as an indicator of Barn Owl Tyto alba breeding biology and the effect of winter severity on Barn Owl reproduction

In the temperate zone, food availability and winter weather place serious constraints on European Barn Owl Tyto alba populations. Using data collected over 22 years in a Swiss population, we analysed the influence of early pre‐breeding food conditions and winter severity on between‐year variations in population size and reproductive performance. To estimate pre‐breeding food conditions, we attempted a novel approach based on an index that combines Tawny Owl Strix aluco reproductive parameters and the occurrence of wood mice Apodemus sp. in their diet. Tawny Owls breed earlier in the season than Barn Owls and are strongly dependent on the abundance of wood mice for breeding. This index was strongly positively associated with the number of breeding pairs and early breeding in the Barn Owl. Winter severity, measured by snow cover and low temperatures, had a pronounced negative influence on the size of the breeding population and clutch size. Food conditions early in the breeding season and winter severity differentially affect the Barn Owl life cycle. We were able to use aspects of the ecology and demography of the Tawny Owl as an indicator of the quality of the environment for a related species of similar ecology, in this case the Barn Owl.     

Synchrony in short-term fluctuations of moose calf body mass and bank vole population density supports the mast depression hypothesis

Inter-annual variations in body mass of moose, Alces alces , in Norway and Sweden have been considered as most likely due to direct or indirect effects of weather, but so far predictions of autumn body mass of moose calves on the basis of weather data have given a poor fit to data. A striking, but hitherto unnoticed, feature of several time series on body mass of moose calves from south-eastern Norway is an apparently regular 3–4-year fluctuation pattern. This short-term fluctuation could be due to regular variations in forage quality, e.g. caused by a cyclic seed production of some important food plants, as envisaged by the "mast depression" hypothesis. One plant species important as food for moose calves in autumn is bilberry, Vaccinium myrtillus , which usually produces high seed crops (masts) at intervals of 3–4 years. Populations of the bank vole, Clethrionomys glareolus, which feeds on bilberry shoots in winter, are known to peak in bilberry post-mast years. In two study areas in Norway, there was a positive correlation between the autumn body mass of moose calves and the autumn population index of bank vole in the succeeding year. In the northern area there was an additional positive effect of summer precipitation, whereas in the southern area there was an additional negative effect of summer temperature. In both areas, however, the effect of weather was less pronounced than that of the bank vole index. These results support the mast depression hypothesis.     

Seasonal changes in condition, nutrition, gonad maturation and energy content in barbel, Barbus sclateri, inhabiting a fluctuating river

The objective of this study was to investigate the seasonal cycle of condition, nutrition and gonad development, as well as the magnitude of seasonal variations in energy content of somatic and gonad tissues in juveniles, males and females of Sclater's barbel, Barbus sclateri, from the upper Guadalete River (south Spain). The influence of reproductive cycle on somatic changes was also investigated and discussed. Measurements of condition factor (K), somatic index (SI), gonadosomatic index (GSI) and somatic and gonad energy content (J g^-1 dw) were made in individual specimens taken from the Guadalete River monthly for 12 months. This freshwater ecosystem is characterised by strong seasonal fluctuations in water and flow level, temperature and food supply. It was found that in general juveniles, males and females of barbel exhibited a similar condition, nutrition and somatic energy cycle throughout the year, with the highest values in spring and the lowest in summer. Depletion of K, SI and somatic energy storage from spring until mid-summer seems to be associated with high metabolic demands during this period, and in adult fish also with spawning-related activity. The gonad index and energy content of the gonad were the highest in April and the lowest in summer for both sexes. Spawning took place during late spring – early summer, with fish quiescent by mid summer. The energy required for ovarian development (3970 J g^-1 dw) was greater than the one for testes development (2763 J g^-1 dw). Data on gonad energy content indicated a period (March to April) of intense energy accumulation (64% males and 37% females) which was related to the decline in the average somatic energy content in males and females. The somatic energy content was linearly related to K and SI. In the same way, GSI correlated positively with gonad energy. Linear trends were found between somatic parameters (K, SI and energy content) and gonad parameters (GSI and energy content). This revised version was published online in July 2006 with corrections to the Cover Date.     

Heat-stress-related mortality in five cities in Southern Ontario: 1980–1996

The Toronto–Windsor corridor of Southern Ontario, Canada, experiences hot and humid weather conditions in summer, thus exposing the population to heat stress and a greater risk of mortality. In the event of a climate change, heat-stress conditions may become more frequent and severe in Southern Ontario. To assess the impact of summer weather on health, we analyzed heat-related mortality in the elderly (older than 64 years) in the metropolitan areas of Windsor, London, Kitchener-Waterloo-Cambridge, Hamilton, and Toronto for a 17-year period. Demographic, socioeconomic, and housing factors were also evaluated to assess their effect on the potential of the population to adapt and their vulnerability to heat stress. Heat-stress days were defined as those with an apparent temperature (heat index) above 32°C. Mortality among the elderly was significantly higher on heat-stress days than on non-heat-stress days in all cities except Windsor. The strongest relationships occurred in Toronto and London, followed by Hamilton. Cities with the greatest heat-related mortality have relatively high levels of urbanization and high costs of living. Even without the warming induced by a climate change, (1) vulnerability is likely to increase as the population ages, and (2) ongoing urban development and sprawl are expected to intensify heat-stress conditions in Southern Ontario. Actions should be taken to reduce vulnerability to heat stress conditions, and to develop a comprehensive hot weather watch/warning system for the region. Received: 9 August 1999 / Revised: 9 March 2000 / Accepted: 1 May 2000     

Effects of an evaporative cooling system on plasma cortisol, IGF-I, and milk production in dairy cows in a tropical environment

Access to an evaporative cooling system can increase production in dairy cows because of improved thermal comfort. This study aimed to evaluate the impact of ambient temperature on thermoregulation, plasma cortisol, insulin-like growth factor 1 (IGF-I), and productive status, and to determine the efficiency of an evaporative cooling system on physiological responses under different weather patterns. A total of 28 Holstein cows were divided into two groups, one with and the other without access to a cooling system with fans and mist in the free stall. The parameters were analyzed during morning (0700 hours) and afternoon milking (1430 hours) under five different weather patterns throughout the year (fall, winter, spring, dry summer, and rainy summer). Rectal temperature (RT), body surface temperature (BS), base of tail temperature (TT), and respiratory frequency (RF) were lower in the morning (P?<?0.01). The cooling system did not affect RT, and both the groups had values below 38.56 over the year (P?=?0.11). Cortisol and IGF-I may have been influenced by the seasons, in opposite ways. Cortisol concentrations were higher in winter (P?<?0.05) and IGF-I was higher during spring-summer (P?<?0.05). The air temperature and the temperature humidity index showed positive moderate correlations to RT, BS, TT, and RF (P?<?0.001). The ambient temperature was found to have a positive correlation with the physiological variables, independent of the cooling system, but cooled animals exhibited higher milk production during spring and summer (P?<?0.01).     

Relative importance of components affecting the leaf rust progress curve in wheat

Summary The relative importance of various components (latent period, uredium area, infectious period, infectibility, sporulation and weather) affecting the progress of leaf rust (Puccinia recondita) in wheat, in the field, was determined by calculating the effect of equivalent changes in the individual components. The effect was calculated in terms of the period of delay in the epidemic reaching 100 per cent severity of leaf rust. Only four components viz., latent period, infectibility, sporulation and weather were found to be important. Further, it was found that these four components were equally important and that they collectively determined the rate of progress of leaf rust in an additive manner.