A comparison of the population growth potential, in California red scale, Aonidiella aurantii (Maskell), and yellow scale, A. citrina (Croquillet) on citris

1971 ◽  
Vol 19 (2) ◽  
pp. 189 ◽  
Author(s):  
IW McLaren
Keyword(s):  
Biological Control ◽  
Population Growth ◽  
Growth Potential ◽  
Natural Control ◽  
Settling Behaviour ◽  
Thermal Death ◽  
Unfertilized Female ◽  
Thermal Death Point ◽  
Yellow Scale ◽  
Scale Control

Successful biological control of A. aurantii and A. citrina has been achieved on many citrus properties in the region of Mildura. A project was undertaken to devise methods for augmenting and extending the natural control of red scale in Victoria. A, aurantii and A. citrina were compared by compiling age-specific life and fecundity tables over a range of temperature and humidities. A mathematical analysis of these data showed that the upper thermal death point was similar for both species, A. citrina multiplied more rapidly than A. aurantii over the median range of temperatures, and the threshold of population growth occurred at about 15260C for A, aurantii and 18260C for A, citrina. An earlier study of the settling behaviour of crawlers indicated that most A. aurantii crawlers settled on the upper surfaces of leaves, due to negative geotaxis, and that crawlers of A. citrina were negatively phototropic and therefore settled on the shaded under surfaces of leaves. In A. aurantii, delayed mating caused a high initial natality. This was thought to result from continuing ovulation in the unfertilized female, a postulate reinforced by the results of an examination of the developing embryos in females mated at various ages. On the basis of this study an improved approach to red scale control is proffered, namely, that attempts be made to increase the mortality of the over- wintering insects.

The Malaria Problem in Mauritius: the Bionomics Of Mauritian Anophelines

1947 ◽  
Vol 38 (1) ◽  
pp. 177-208 ◽  
Author(s):  
W. F. Jepson ◽  
A. Moutia ◽  
C. Courtois
Keyword(s):  
Low Temperatures ◽  
Limiting Factor ◽  
Natural Control ◽  
Colloidal Iron ◽  
Thermal Death ◽  
Service Areas ◽  
History Of ◽  
Thermal Death Point ◽  
Adverse Influence ◽  
Heavy Rains

1. A sketch is given of the Malaria Control Organisation in Service areas in Mauritius with a summarised history of malaria work in the Island since the first epidemic in 1865.2. Keys to Mauritian Anophelines and their larvae with notes on their field recognition characters are followed by data on the distribution of adult Anophelines in the Colony and their relation to malaria intensity in different areas. A. melas appears to be absent from coastal swamps.3. The influence of a number of environmental factors is discussed. It is concluded that temperature is an important limiting factor generally in winter and perennially in the highlands (above 1,000 ft.), but that the flushing action of heavy rains and probably the precipitation of food supply by colloidal iron moving under high rainfall conditions (over 100 ins.) from ferrugineous lavas both play their part in the natural control of A. funestus and A. gambiae.The behaviour of A. gambiae with respect to temperature is expressed by an area enclosed by two symmetrical catenary curves, that illustrate well the adverse influence on development of low temperatures normally occurring in winter on the coast and all the year round in the residential uplands above 1,000 ft. The thermal death point of A. gambiae larvae is about 42°C. and that of A. funestus 40°C. and the lower limit of larval activity is 16·5°C. A. gambiae develops most rapidly at an estimated temperature of about 37°C.

Thermal Death Point: I. Spores of Clostridium Tetani

1931 ◽  
Vol 48 (5) ◽  
pp. 436-456 ◽  
Author(s):  
T. J. Murray ◽  
M. R. Headlee
Keyword(s):  
Clostridium Tetani ◽  
Thermal Death ◽  
Thermal Death Point

scholarly journals Influence of Temperature on Age-Stage, Two-Sex Life Tables for a Minnesota-Acclimated Population of the Brown Marmorated Stink Bug (Halyomorpha halys)

Insects ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 108 ◽  
Author(s):  
Byju N. Govindan ◽  
William D. Hutchison
Keyword(s):  
Population Growth ◽  
Life Table ◽  
Growth Potential ◽  
Intrinsic Rate Of Increase ◽  
Halyomorpha Halys ◽  
Brown Marmorated Stink Bug ◽  
Stink Bug ◽  
Current Limit ◽  
Rate Of Increase ◽  
Survival And Reproduction

Temperature is a critical single factor influencing insect population dynamics, and is foundational for improving our understanding of the phenology of invasive species adapting to new agroecosystems or in the process of range expansion. An age-stage, two-sex life table was therefore developed to analyze fundamental demographic features such as development, survival, and reproduction of a Minnesota-acclimated population of the invasive brown marmorated stink bug (Halyomorpha halys), in the north central USA. All salient life history parameters were estimated to better understand the population growth potential of H. halys at the current limit of its northern range in North America. We examined the effect of selected constant temperatures on immature development and survival (15–39 °C), adult reproduction and longevity (17–36 °C) of H. halys in the laboratory. The Minnesota population developed faster and survived at higher rates relative to a population that had previously established in Pennsylvania, USA. Mean generation time for the Minnesota population was minimized at 30 °C, while survival and fecundity were maximized at 27 and 23 °C, respectively. Given these findings, we assessed the effect of temperature on the intrinsic rate of increase ( r m ), the life table parameter that integrates the effects of temperature on development, survival, and reproduction. A Ratkowsky model predicted r m was maximized (0.0899) at 27.5 °C. We discuss the implications of our findings for understanding population growth rates for H. halys in the context of a warming climate, and potential to emerge as a serious crop pest in the Midwest U.S. region.

scholarly journals High pregnancy rates in humpback whales ( Megaptera novaeangliae ) around the Western Antarctic Peninsula, evidence of a rapidly growing population

2018 ◽  
Vol 5 (5) ◽  
pp. 180017 ◽  
Author(s):  
Logan J. Pallin ◽  
C. Scott Baker ◽  
Debbie Steel ◽  
Nicholas M. Kellar ◽  
Jooke Robbins ◽  
...  
Keyword(s):  
Population Growth ◽  
Antarctic Peninsula ◽  
Pregnancy Rates ◽  
Growth Potential ◽  
Humpback Whales ◽  
Western Antarctic Peninsula ◽  
Tissue Samples ◽  
Commercial Whaling ◽  
Reproductive Rates ◽  
The Impact

Antarctic humpback whales are recovering from near extirpation from commercial whaling. To understand the dynamics of this recovery and establish a baseline to monitor impacts of a rapidly changing environment, we investigated sex ratios and pregnancy rates of females within the Western Antarctic Peninsula (WAP) feeding population. DNA profiling of 577 tissue samples (2010–2016) identified 239 males and 268 females. Blubber progesterone levels indicated 63.5% of the females biopsied were pregnant. This proportion varied significantly across years, from 36% in 2010 to 86% in 2014. A comparison of samples collected in summer versus fall showed significant increases in the proportion of females present (50% to 59%) and pregnant (59% to 72%), consistent with demographic variation in migratory timing. We also found evidence of annual reproduction among females; 54.5% of females accompanied by a calf were pregnant. These high pregnancy rates are consistent with a population recovering from past exploitation, but appear inconsistent with recent estimates of WAP humpback population growth. Thus, our results will help to better understand population growth potential and set a current baseline from which to determine the impact of climate change and variability on fecundity and reproductive rates.

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