Spatial and temporal population patterns of Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae) parasitoids (Hymenoptera: Aphelinidae and Encyrtidae) caught on yellow sticky traps in citrus

1986 ◽  
Vol 76 (2) ◽  
pp. 265-274 ◽  
Author(s):  
M. J. Samways
Keyword(s):  
Spatial Distribution ◽  
Management Practices ◽  
Host Density ◽  
Population Level ◽  
Sticky Trap ◽  
Aonidiella Aurantii ◽  
Final Population ◽  
Parasitoid Population ◽  
Yellow Sticky Trap ◽  
Seasonal Population

AbstractParasitoids of Aonidiella aurantii (Maskell) on citrus in South Africa were monitored using two types of yellow sticky trap. One of these traps was highly efficient, being fluorescent with peak reflectance at about 530 nm. Aphytis spp. populations were low before February and high thereafter. Citrus surrounded by natural bush was an isolated reservoir of high host and parasitoid population levels. Aphytis spatial distribution within the orchard was extremely patchy, with over 100-fold differences in population levels over a distance of a few metres. This patchiness mirrored that of its host. This contagious spatial pattern was maintained despite 1000-fold seasonal changes in population levels. These temporal changes were characteristic and general throughout an orchard, and independent of patchiness. Initial Aphytis population levels did not dictate the final population level at the end of the season. Comperiella bifasciata Howard and its hyperparasitoid Marietta javensis (Howard) also showed clear seasonal population trends, but not of the same magnitude as those of Aphytis. There was no statistically significant correlation between the spatial distribution of one parasitoid with that of another, even between C. bifasciata and M. javensis. The patchiness of these two species was not correlated with overall host density. Aphytis and C. bifasciata were partially mutually exclusive. Aphytis was by far the most economically important of the parasitoids. Pest management practices, therefore, should aim at conserving the pool of Aphytis within the orchard as far as practicable.

scholarly journals Maggot Control, 1997

1998 ◽  
Vol 23 (1) ◽  
pp. 49-50
Author(s):  
J. A. Collins ◽  
F. A. Drummond
Keyword(s):  
Management Practices ◽  
Sticky Trap ◽  
Water Mixture ◽  
Flow Meter ◽  
Current Management ◽  
Ground Speed ◽  
Threshold Levels ◽  
Plot Size ◽  
Untreated Check ◽  
Yellow Sticky Trap

Abstract Test materials were applied to plots in bearing blueberry fields at Deblois (Tests 1 and 2) and Township 19 (Tests 3 and 4), Maine. Timing for each application is given in the table. Treatment plot size measured 100 X 300-ft for Test 1, 150 X 300-ft for Test 2, and 200 X 300-ft for Tests 3 and 4. An untreated area adjacent to each plot or set of treated plots was designated as a control. The first application was made when yellow sticky trap captures indicated that BM populations had exceeded threshold levels as defined by current management practices (6 flies at any one visit or 10+ flies over 2 or more visits). Materials were applied using a Cessna Ag Wagon® equipped with 30 CP nozzles on 2½-inch drop tubes and calibrated with a #7 Crop Hawk® Flow Meter to deliver 5 (Sniper) or 6 (Imidan) pints of water-mixture per acre. Ground speed =120 mph; 2500 RPM; pressure at boom = 40 psi; height = 5-8 ft; 50 ft swath. On 4 Aug (Tests 3 and 4) and 8 Aug (Tests 1 and 2), one quart of berries was raked from each of 10 or 15 preselected subsites within each treated and untreated check plot and at least 25 ft from plot boundaries. Berries were refrigerated and processed for maggots within 2 weeks of collection. Weather during the trial was very dry. Only 1.57 inches of rain was recorded between 1 Jul and 8 Aug.

scholarly journals Host density predicts the probability of parasitism by avian brood parasites

2019 ◽  
Vol 374 (1769) ◽  
pp. 20180204 ◽  
Author(s):  
Iliana Medina ◽  
Naomi E. Langmore
Keyword(s):  
Spatial Distribution ◽  
Reproductive Success ◽  
Host Species ◽  
Field Data ◽  
Host Density ◽  
Brood Parasites ◽  
Parasitism Rates ◽  
Analyse Data ◽  
First Time ◽  
Determining Factor

The spatial distribution of hosts can be a determining factor in the reproductive success of parasites. Highly aggregated hosts may offer more opportunities for reproduction but can have better defences than isolated hosts. Here we connect macro- and micro-evolutionary processes to understand the link between host density and parasitism, using avian brood parasites as a model system. We analyse data across more than 200 host species using phylogenetic comparative analyses and quantify parasitism rate and host reproductive success in relation to spatial distribution using field data collected on one host species over 6 years. Our comparative analysis reveals that hosts occurring at intermediate densities are more likely to be parasitized than colonial or widely dispersed hosts. Correspondingly, our intraspecific field data show that individuals living at moderate densities experience higher parasitism rates than individuals at either low or high densities. Moreover, we show for the first time that the effect of host density on host reproductive success varies according to the intensity of parasitism; hosts have greater reproductive success when living at high densities if parasitism rates are high, but fare better at low densities when parasitism rates are low. We provide the first evidence of the trade-off between host density and parasitism at both macro- and micro-evolutionary scales in brood parasites. This article is part of the theme issue ‘The coevolutionary biology of brood parasitism: from mechanism to pattern’.

scholarly journals Population Dynamics of Released Potato Psyllids and their Bacteriliferous Status in Relation to Zebra Chip Incidence in Caged Field Plots

Plant Disease ◽  
2016 ◽  
Vol 100 (8) ◽  
pp. 1762-1767 ◽  
Author(s):  
F. Workneh ◽  
L. Paetzold ◽  
A. Rashed ◽  
C. M. Rush
Keyword(s):  
Disease Incidence ◽  
Sticky Trap ◽  
Research Station ◽  
Zebra Chip ◽  
Sticky Traps ◽  
Monitoring Tools ◽  
Candidatus Liberibacter ◽  
Yellow Sticky Trap ◽  
Successive Generations ◽  
Field Plots

Potato psyllids vector ‘Candidatus Liberibacter solanacearum’ (Lso), the putative causal agent of potato zebra chip (ZC). Currently, sticky traps are the primary psyllid monitoring tools used by growers for making management decisions. However, the reliability of sticky traps in predicting psyllid numbers in potato fields has always been questioned. In 2013 and 2014, experiments were conducted in covered field plots at the Texas A&M AgriLife Research Station at Bushland to investigate the relationships among initial psyllid numbers, psyllids captured on sticky traps and their Lso status, and zebra chip incidence. Three densities of Lso-positive psyllids (5, 15, or 30/cage) were released under 2-week-old potato canopies with four replications in plot sizes of 7.6 to 9 m by 5 rows. Psyllids were released under the first plant in the center row and monitored weekly with a yellow sticky trap from the opposite end. Number of plants with zebra chip symptoms also was counted weekly beginning one month after infestation with psyllids. The total number of psyllids captured on sticky traps and disease incidence levels generally corresponded to the levels of psyllid density treatments (5 < 15 < 30), but the differences became more apparent toward the end of the experiments. Psyllid numbers in the different density treatments fluctuated more or less in synchrony over time, which appeared to reflect periodic emergence of new generations of psyllids. Initially, all captured psyllids tested positive for Lso. However, the proportions of psyllids testing positive declined dramatically after a few weeks, which suggested that the new generations of psyllids were devoid of Lso. Over all, less than 50% of captured psyllids tested positive for the pathogen. The decline in proportions of psyllids testing positive for Lso following successive generations has significant relevance to field situations and may partly explain why there are generally low percentages of Lso-positive psyllids under field conditions.

Spatial variability of the physical-hydric properties of cohesive soils under rainfed and irrigated sugarcane cultivations

2021 ◽  
Author(s):  
Brivaldo Gomes de Almeida ◽  
Bruno Campos Mantovanelli ◽  
Thiago Rodrigo Schossler ◽  
Fernando José Freire ◽  
Edivan Rodrigues de Souza ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Spatial Variability ◽  
Structural Changes ◽  
Management Practices ◽  
Geometric Mean ◽  
Soil Layer ◽  
Multivariate Techniques ◽  
Geostatistical Approach ◽  
Physical Attributes ◽  
Soil Spatial Variability

&lt;p&gt;Geostatistical and multivariate techniques have been widely used to identify and characterize the soil spatial variability, as well as to detect possible relationships between soil properties and management. Besides that, these techniques provide information regarding the spatial and temporal structural changes of soils to support better decision-making processes and management practices. Although the Zona da Mata region is a reference for sugarcane production in the northeast of Brazil, only a few studies have been carried out to clarify the effects of different management on soil physical attributes by using geostatistical and multivariate techniques. Thus, the objectives of this study were: (I) to characterize the spatial distribution of soils physical attributes under rainfed and irrigated sugarcane cultivations; (II) to identify the minimum sampling for the determination of soil physical attributes; (III) to detect the effects of the different management on soil physical attributes based on the principal component analysis (PCA). The study was carried out in the agricultural area of the Carpina Sugarcane Experimental Station of the Federal Rural University of Pernambuco, 7&amp;#186;51&amp;#8217;13&amp;#8221;S, 35&amp;#186;14&amp;#8217;10&amp;#8221;W, characterized by a Typic Hapludult with sandy clay loam soil texture. The investigated plot, cultivated with sugarcane, included a rainfed and an irrigated treatment in which a sprinkler system was installed according to a 12x12m grid. The interval between consecutive watering was fixed in two days, whereas irrigation depth was calculated to replace crop evapotranspiration (ETc) and accounting for the effective precipitation of the period. Daily ETc was estimated based on crop coefficient and reference evapotranspiration (ETo) indirectly obtained through a class A evaporation pan. In both treatments, the soil spatial variability was determined according to a 56x32m grid, on 32 soil samples collected in the 0.0-0.1m soil layer, spaced 7x8m, and georeferenced with a global position system. The soil was physically characterized according to the following attributes: bulk density (BD), soil penetration resistance (SPR), macroporosity (Macro), mesoporosity (Meso), microporosity (Micro), total porosity (TP), saturated hydraulic conductivity (Ksat), gravimetric soil water content (SWCg), geometric mean diameter (GMD) and mean weight diameter (MWD). The results of the descriptive statistics showed that among the studied attributes, Ksat, SPR, and Macro presented higher CV values, equal to 63 and 69%, 35 and 40%, and 32 and 44%, under rainfed and irrigated conditions, respectively. The minimum sampling, adequate to characterize the different soil attributes, resulted in general smaller in the rainfed area, characterized by higher homogeneity. Thus, the GMD, SWCg (both with 2 points ha&lt;sup&gt;-1&lt;/sup&gt;), and SPR (with 6 points ha&lt;sup&gt;-1&lt;/sup&gt;) were identified as the soil physical attributes requiring the lowest sample density; on the other hand, MWD and Ksat, with 14 and 15 points ha&lt;sup&gt;-1&lt;/sup&gt;, respectively, required the highest number of samples. Pearson&amp;#8217;s correlation analysis evidenced that soil BD was the most influential physical attribute in the studied areas, with a significant and inverse effect in most of the investigated attributes. The geostatistical approach associated with the multivariate PCA provided to understand the relationships between the spatial distribution patterns associated with irrigated and rainfed management and soil physical properties.&lt;/p&gt;

scholarly journals Identifying Ways to Narrow Maize Yield Gaps Based on Plant Density Experiments

Agronomy ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 281
Author(s):  
Jian Li ◽  
Man Wu ◽  
Keru Wang ◽  
Bo Ming ◽  
Xiao Chang ◽  
...  
Keyword(s):  
Management Practices ◽  
Field Experiments ◽  
Plant Density ◽  
Population Level ◽  
Maize Yield ◽  
Limiting Factors ◽  
Stable Range ◽  
Maize Production ◽  
Yield Gaps ◽  
Loss Range

Exploring the maximum grain yields (GYs) and GY gaps in maize (Zea mays L.) can be beneficial for farmer to identify the GY-limiting factors and take adaptive management practices for a higher GY. The objective of this work was to identify the optimum maize plant density range and the ways to narrow maize GY gaps based on the variation of the GYs, dry matter (DM) accumulation and remobilization with changes in plant density. Field experiments were performed at the 71 Group and Qitai Farm in Xinjiang, China. Two modern cultivars, ZhengDan958 and ZhongDan909, were planted at 12 densities, ranging from 1.5 to 18 plants m−2. With increased plant density, single plant DM decreased exponentially, whereas population-level DM at the pre- (DMBS) and post- (DMAS) silking stages increased, and the amount of DM remobilization (ARDM) increased exponentially. Further analysis showed that plants were divided four density ranges: range I (<6.97 plants m−2), in which no DM remobilization occurred, DMBS and DMAS correlated significantly with GY; range II (6.97–9.54 plants m−2), in which the correlations of DMBS, DMAS, and ARDM with GY were significant; range III (9.54–10.67 plants m−2), in which GY and DMAS were not affected by density, DMBS increased significantly, and only the correlation of DMAS with GY was significant; and range IV (>10.67 plants m−2), in which the correlations of DMBS and ARDM with GY decreased significantly, while that of DMAS increased significantly. Therefore, ranges I and II were considered to be DM-dependent ranges, and a higher GY could be obtained by increasing the population-level DMAS, DMAS, and ARDM. Range III was considered the GY-stable range, increasing population-level DMBS, as well as preventing the loss of harvest index were the best way to enhance maize production. Range IV was interpreted as the GY-loss range, and a higher GY could be obtained by preventing the loss of HI and population-level DMAS.

scholarly journals Abundance and genetic diversity responses of a lizard (Eulamprus heatwolei) to logging disturbance

2017 ◽  
Vol 65 (6) ◽  
pp. 362
Author(s):  
Francesca Lyndon-Gee ◽  
Joanna Sumner ◽  
Yang Hu ◽  
Claudio Ciofi ◽  
Tim S. Jessop
Keyword(s):  
Genetic Diversity ◽  
Forest Management ◽  
Management Practices ◽  
Forest Disturbance ◽  
Population Level ◽  
Landscape Scale ◽  
Population Abundance ◽  
Animal Populations ◽  
Eastern Australia ◽  
Logging Disturbance

Rotational logging practices are used with the goal of reducing forest disturbance impacts on biodiversity. However, it is poorly understood whether such forest management practices conserve the demographic and genetic composition of animal populations across logged landscapes. Here we investigated whether rotational logging practices alter patterns of landscape-scale population abundance and genetic diversity of a forest-dwelling lizard (Eulamprus heatwolei) in south-eastern Australia. We sampled lizards (n = 407) at up to 48 sites across a chronosequence of logging disturbance intervals (<10 to >60 years after logging) to assess site-specific population changes and genetic diversity parameters. Lizard abundances exhibited a significant curvilinear response to time since logging, with decreased numbers following logging (<10 years), increased abundance as the forest regenerated (10–20 years), before decreasing again in older regenerated forest sites (>30 years). Lizard genetic diversity parameters were not significantly influenced by logging disturbance. These results suggest that logging practices, whilst inducing short-term changes to population abundance, had no measurable effects on the landscape-scale genetic diversity of E. heatwolei. These results are important as they demonstrate the value of monitoring for evaluating forest management efficacy, and the use of different population-level markers to make stronger inference about the potential impacts of logging activities.

scholarly journals Bridging the gap: global disparity processing in the human visual cortex

2012 ◽  
Vol 107 (9) ◽  
pp. 2421-2429 ◽  
Author(s):  
Benoit R. Cottereau ◽  
Suzanne P. McKee ◽  
Anthony M. Norcia
Keyword(s):  
Spatial Distribution ◽  
Population Level ◽  
Neural Substrates ◽  
Regions Of Interest ◽  
Inverse Technique ◽  
Lateral Occipital Complex ◽  
Reference Information ◽  
Depth Discrimination ◽  
Edge Detectors ◽  
Stereoscopic System

The human stereoscopic system is remarkable in its ability to utilize widely separated features as references to support fine depth discrimination. In a search for possible neural substrates of this ability, we recorded high-density EEG and used a distributed inverse technique to estimate population-level disparity responses in five regions of interest (ROIs): V1, V3A, hMT+, V4, and lateral occipital complex (LOC). The stimulus was a central modulating disk surrounded by a correlated “reference” annulus presented in the fixation plane. We varied a gap separating the disk from the annulus parametrically from 0 to 5.5° as a test of long-range disparity integration. In the V1, LOC, and hMT+ ROIs, the responses with gaps >0.5° were equal to those obtained in a control condition where the surround was composed of uncorrelated noise (no reference). By contrast, in the V4 and V3A ROIs, responses with gaps as large as 5.5° were still significantly higher than the control. As a test of the spatial distribution of the disparity reference information, we manipulated the properties of the stimulus by placing noise between the center and the surround or throughout the surround. The V3A ROI was particularly sensitive to disparity noise between the center and annulus regions, suggesting an important contribution of disparity edge detectors in this ROI.

scholarly journals Population Dynamics of the Lance Nematode (Hoplolaimus galeatus) in Creeping Bentgrass

Plant Disease ◽  
2006 ◽  
Vol 90 (1) ◽  
pp. 44-50 ◽  
Author(s):  
D. M. Settle ◽  
J. D. Fry ◽  
T. C. Todd ◽  
N. A. Tisserat
Keyword(s):  
Management Practices ◽  
Creeping Bentgrass ◽  
Population Increase ◽  
Irrigation Frequency ◽  
Final Population ◽  
Cultivar Selection ◽  
Nematode Population Density ◽  
Putting Green ◽  
Hoplolaimus Galeatus ◽  
Lance Nematode

The effects of management practices and nematode population density on the seasonal fluctuationsin lance nematode (Hoplolaimus galeatus) populations in creeping bentgrass were studiedin a naturally infested experimental putting green and in artificially infested microplots. In general, H. galeatus populations increased from late spring through midsummer, declined in August, and increased again in the fall. Population increase in microplots was strongly density dependent, with final population densities inversely proportional to inoculum levels. Ectoparasitic populationsof H. galeatus in both studies were composed of adults and juveniles, whereas endoparasiticpopulations were almost exclusively juveniles. H. galeatus populations in the naturallyinfested site were aggregated spatially, but the aggregation was not temporally stable. Nematodepopulations were not affected by bentgrass cultivar selection or irrigation frequency.

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