scholarly journals Non-linear relationship between food resource exploitation and population density of stored-product pests

2000 ◽  
Vol 18 (No. 3) ◽  
pp. 81-85 ◽  
Author(s):  
V. Stejskal
Keyword(s):  
Population Density ◽  
Food Resource ◽  
Food Products ◽  
Population History ◽  
Resource Exploitation ◽  
Pest Population ◽  
Critical Thresholds ◽  
Pest Infestation ◽  
Stored Product Pests ◽  
Food Commodities

  The main current strategies (IPM, HACCP) to control pests in stored food products are based on critical thresholds derived from pest population density. These thresholds usually do not consider cumulative effects of earlier pest infestation although injuries caused by biotic pest organisms to stored food commodities are irreversible. We present conceptual and illustrative models showing that population size indices, in contrast to cumulative (population history) indices, could (i) underestimate critical thresholds if pest population can grow exponentially and (ii) provide incorrect information about the level of stored food damage if pest population density can fluctuate. The importance of entomological food microanalysis and continual “cumulative monitoring” based on trapping is discussed with respect to HACCP and IPM programmes in stored food products.

scholarly journals Development of Reverse Transcription (RT)-PCR and Real-Time RT-PCR Assays for Rapid Detection and Quantification of Viable Yeasts and Molds Contaminating Yogurts and Pasteurized Food Products

2003 ◽  
Vol 69 (7) ◽  
pp. 4116-4122 ◽  
Author(s):  
Gianluca Bleve ◽  
Lucia Rizzotti ◽  
Franco Dellaglio ◽  
Sandra Torriani
Keyword(s):  
Real Time ◽  
Food Products ◽  
Fungal Species ◽  
Universal Primers ◽  
Rt Pcr ◽  
Specificity And Sensitivity ◽  
Actin Mrna ◽  
Pcr Assays ◽  
Food Commodities ◽  
Yeasts And Molds

ABSTRACT Reverse transcriptase PCR (RT-PCR) and real-time RT-PCR assays have been used to detect and quantify actin mRNA from yeasts and molds. Universal primers were designed based on the available fungal actin sequences, and by RT-PCR they amplified a specific 353-bp fragment from fungal species involved in food spoilage. From experiments on heat-treated cells, actin mRNA was a good indicator of cell viability: viable cells and cells in a nonculturable state were detected, while no signal was observed from dead cells. The optimized RT-PCR assay was able to detect 10 CFU of fungi ml−1 in pure culture and 103 and 102 CFU ml−1 in artificially contaminated yogurts and pasteurized fruit-derived products, respectively. Real-time RT-PCR, performed on a range of spoiled commercial food products, validated the suitability of actin mRNA detection for the quantification of naturally contaminating fungi. The specificity and sensitivity of the procedure, combined with its speed, its reliability, and the potential automation of the technique, offer several advantages to routine analysis programs that assess the presence and viability of fungi in food commodities.

Effects of food, kinship, and density on the longevity of spiderlings

2021 ◽  
pp. 741-751
Author(s):  
Marta Luciane Fischer ◽  
Lays Cherobim Parolin ◽  
Felipe Marcel Neves ◽  
German Antonio Villanueva-Bonilla ◽  
João Vasconellos-Neto
Keyword(s):  
Population Density ◽  
Laboratory Experiments ◽  
Survival Rates ◽  
Food Resource ◽  
Behavioral Characteristic ◽  
Risk Of Predation ◽  
Large Populations ◽  
Main Factors ◽  
Conspecific Tolerance ◽  
Loxosceles Laeta

Cannibalism is a behavioral characteristic found in a wide variety of animal groups. Although the rates of cannibalism can vary from one group to another, studies indicate that the main factors contributing to an increase in the frequency of such behavior are the availability of food, population density, the behavior and availability of victims, and environmental stress. We carried out different laboratory experiments to assess whether different factors such as the presence or absence of food among siblings and non-siblings, and at different densities among conspecific and heterospecific individuals, affect longevity of recently emerged Brazilian brown recluse (Loxosceles intermedia Mello-Leitão, 1934) and Chilean recluse (Loxosceles laeta (Nicolet, 1849)) spiderlings during periods of starvation. The results revealed that the survivorship of L. laeta during starvation was significantly higher than that of L. intermedia and that the addition of conspecific individuals increased survival rates by 1.5- and 1.6-fold, respectively. The tolerance of conspecifics differed between the two species, and generally, cannibalism was not observed, probably due to the risk of predation and limited consumption by weakened spiders, which coincided with the continued availability of endogenous vitelline reserves, thus indicating that the use of these spiderlings as a food resource may act to regulate starvation in more resistant spiders. The greater longevity and conspecific tolerance of L. laeta may be important factors contributing to the establishment of large populations of this spider in restricted areas, whereas for L. intermedia, hunger probably functions as a trigger for dispersal.

Space use by female agile antechinus: are teat number and home-range size linked?

2016 ◽  
Vol 43 (4) ◽  
pp. 348 ◽  
Author(s):  
Juliey Beckman ◽  
Alan Lill
Keyword(s):  
Population Density ◽  
Home Range ◽  
Food Resource ◽  
Food Abundance ◽  
Energetic Cost ◽  
Home Ranges ◽  
Female Population ◽  
Eastern Australia ◽  
Minimal Convex ◽  
Teat Number

Context The number of teats that a female agile antechinus (Antechinus agilis) possesses effectively determines her initial litter size. In the Otway Ranges, south-eastern Australia, numerous separate populations in which all females have either six or 10 teats occur fairly close together in similar, contiguous forest at comparable altitudes and latitudes. Six-teat and 10-teat females have a similar mean mass, but the latter have a 1.7 × greater reproductive potential and so should have a greater nutritional requirement while raising young than do six-teat females. Theoretically, they could meet this requirement by occupying larger and/or more exclusive home ranges during breeding than do six-teat females do (provided that their food-resource abundance is comparable), albeit at a greater energetic cost. Aims The aim of the study was to determine whether 10-teat A. agilis females occupied larger and less overlapping home ranges than did six-teat females. To interpret the findings more meaningfully, it was necessary to compare food abundance and habitat characteristics in areas occupied by the two phenotypes. Methods The investigation was conducted in six-teat and 10-teat A. agilis areas in cool temperate forest over 22 months. Population density was determined by mark–recapture methods and arthropod prey biomass and abundance by pitfall trapping. Vegetation structure and plant-taxa abundance and diversity were determined by standard plant-survey methods. Female home-range estimates determined by radio-tracking were based on 95% minimal convex polygons (MCP) and kernel analysis. Home-range overlap was based on 80% MCP range determinations and core areas were calculated from utilisation plots. Key results Female population density was 2.5 × lower in exclusively 10-teat than in exclusively six-teat populations. Radio-tracked 10-teat females’ home ranges less commonly overlapped those of identified female neighbours and, on average, were 1.5 × larger than ranges of six-teat females. Food abundance and composition was similar in six-teat and 10-teat areas, but ground cover was denser and more complex in the latter areas. Conclusions Food-resource availability was similar in the six-teat and 10-teat phenotype areas, so the larger, and probably more exclusive, home ranges of 10-teat females could reflect greater nutritional requirements resulting from having larger litters, and account for their lower population density. Implications The A. agilis teat-number variation pattern in the Otways may be a rare, visible example of ongoing incipient speciation. This makes it of great scientific and conservation value and it is important to document how the phenomenon operates.

scholarly journals Pengaruh Kepadatan Populasi Sitophilus oryzae (L.) terhadap Pertumbuhan Populasi dan Kerusakan Beras

Biospecies ◽  
2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Hendrival HENDRIVAL ◽  
Lilis MELINDA
Keyword(s):  
Population Density ◽  
Population Growth ◽  
Sitophilus Oryzae ◽  
Pest Population ◽  
Positive Correlation ◽  
Weight Percentage ◽  
The Relationship ◽  
Density Population ◽  
Growing Population

The research aims to study the effect population density of S. oryzae against population growth and damage of rice. The population density of S. oryzae is 5, 10, 15, and 20 pairs of adult per 250 g rice. The results showed that population density S. oryzae affects pest population growth of S. oryzae, characteristics loses weight of rice, percentage powder of rice, and changes content moisture of rice. The population density S. oryzae as many as 20 pairs of adult per 250 g of rice can increase populations pest S. oryzae, characteristics loses weight of rice, percentage powder of rice, and content moisture of rice. The relationship between population density S. oryzae with a growing population, percentage loses weight, percentage rice hollow, percentage powder of rice, and changes content moisture of rice increased linearly. There is a positive correlation between population density S. oryzae with population growth S. oryzae (r = 0.997**; P < 0.01), the percentage loses weight (r = 0.987*; P < 0.05), the percentage of rice perforated (r = 0.998**; P < 0.01), the percentage powder of rice (r = 0.997**; P < 0.01), and changes content moisture of rice (r = 0.964**; P < 0.01)Keywords: Sitophilus oryzae, population density, population growth, damage rice

GHSIM Developed in Spreadsheet Quattro Pro Simulates the Interactive Greenhouse

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 448c-448
Author(s):  
Douglas A. Hopper
Keyword(s):  
Plant Growth ◽  
Growth Increment ◽  
Pest Population ◽  
Daily Growth ◽  
Greenhouse Production ◽  
Pest Infestation ◽  
Inhibition Of Growth ◽  
Population Spread ◽  
Repeated Applications ◽  
Daily Growth Increment

A computer model, GHSIM, was formulated in Quattro Pro spreadsheet format. GHSIM was designed having individual pages calculating simulated activities necessary for greenhouse production. Pages were arranged by alphabetical topics starting with the “Area” used in the greenhouse. Time advanced by 1 day for each 10 s of real time. The time advance in the program can be paused to make setting changes interactively. Pest infestation occurred as probabilities accumulated, and the pest population spread through the greenhouse based on proximity and density of pests. Pest control was simulated by a pesticide application capable of partially reducing populations; repeated applications could effectively eliminate a pest. Crop growth was simulated by iterative acccumulation of biomass using Euler integration of daily plant growth. The daily growth increment was calculated using the first derivative of the Richard's Function. Large pest populations negatively impacted the daily growth increment, and pesticide applicaions would remove the inhibition of growth. Additional features proposed include light and temperature effects on the plant growth rate and accumulated biomass.

REPRODUCTIVE CAPACITY OF TWO STRAINS OF CRYPTOLESTES TURCICUS (COLEOPTERA: CUCUJIDAE)

1968 ◽  
Vol 100 (2) ◽  
pp. 198-199
Author(s):  
P. S. Barker ◽  
James A. Johnston
Keyword(s):  
Population Density ◽  
Block Design ◽  
Insect Pest ◽  
The Other ◽  
Reproductive Capacity ◽  
Design Experiment ◽  
Pest Infestation ◽  
Randomized Block Design ◽  
Flour Mill ◽  
Cryptolestes Turcicus

Cryptolestes turcicus (Grouvelle), an insect pest of flour mills and warehouses, is distributed in Canada from Alberta to Quebec (Sinha 1965). Barker (1967) showed a difference in susceptibility to methyl bromide between two strains of C. turcicus; one of these was from the Pest Infestation Laboratory, Slough, England, and the other was from a local flour mill. A fortuitous observation suggested that there might be a difference between the reproductive capacities of these two strains. A randomized block design experiment was designed to test this hypothesis. Reproduction was observed in three sets of beetles differing in population density; each set was replicated four times.

Population ecology of the nectar-feeding squirrel glider (Petaurus norfolcensis) in remnant forest in subtropical Australia

2010 ◽  
Vol 37 (2) ◽  
pp. 77 ◽  
Author(s):  
David J. Sharpe ◽  
Ross L. Goldingay
Keyword(s):  
Population Density ◽  
Population Ecology ◽  
Food Resource ◽  
First Year ◽  
Nectar Feeding ◽  
Remnant Habitat ◽  
Squirrel Glider ◽  
Remnant Forest ◽  
Nectar Availability ◽  
Natality Rate

Context. Nectar is a temporally variable food resource. However, because few studies describe the population dynamics of nectar-feeding non-flying mammals, it is unclear how such populations are influenced by resource availability. Aims. We investigated the population ecology of the squirrel glider (Petaurus norfolcensis) in remnant forest in Brisbane, Australia, where nectar was a dominant food item. Methods. We used 36 tree-mounted traps to census a squirrel glider population inhabiting a 47-ha urban remnant over a 4-year period. Key results. A total of 201 gliders was captured 705 times in 3729 trap-nights (19% trap success). Population density peaked in the first year at ~1.6 individuals ha–1, and declined down to ~0.5 individuals ha–1 by the final year. This change in population density appeared to be mediated by annual variation in flowering intensity. Births occurred from March to November, peaking between April and July. All females >1 year old bred in each year of the study, with a mean litter size of 1.7 (n = 122). The overall natality rate was 1.9, indicating that females occasionally bred twice per year. The sex ratio was at parity in the pouch and in the trappable population. Gliders first entered the trappable population at 4 months of age, and persisted for a mean of 32 months. The maximum longevity was at least 6 years. Conclusions. The demographic characteristics of this squirrel glider population within remnant forest surrounded by urban development were similar to those reported elsewhere. Variation in nectar availability appears to have a substantial influence on the dynamics of squirrel glider populations. Implications. The substantial variation in population size driven by food availability raises concerns regarding the viability of small populations of nectarivorous non-flying mammals inhabiting remnant habitat.

The prehistoric pile-dwelling settlement of Stagno (Leghorn, Italy): wood and food resource exploitation

2010 ◽  
Vol 37 (6) ◽  
pp. 1260-1268 ◽  
Author(s):  
G. Giachi ◽  
M. Mori Secci ◽  
O. Pignatelli ◽  
P. Gambogi ◽  
M. Mariotti Lippi
Keyword(s):  
Food Resource ◽  
Resource Exploitation
Sign in / Sign up

Export Citation Format

Share Document