scholarly journals Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 321
Author(s):  
Stefan Cristian Prazaru ◽  
Giulia Zanettin ◽  
Alberto Pozzebon ◽  
Paola Tirello ◽  
Francesco Toffoletto ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Studies ◽  
Generalist Predators ◽  
Predator Species ◽  
Potted Plants ◽  
Naturally Occurring ◽  
Orius Majusculus ◽  
Limited Effectiveness ◽  
Pest Outbreaks ◽  
The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

scholarly journals Studies Aimed at Evaluating the Impact of Generalist Predators on the Leafhopper Erasmoneura vulnerata Populations

2021 ◽  
Author(s):  
Stefan Cristian Prazaru ◽  
Giulia Zanettin ◽  
Alberto Pozzebon ◽  
Paola Tirello ◽  
Francesco Toffoletto ◽  
...  
Keyword(s):  
Field Experiments ◽  
Generalist Predators ◽  
Recent Issue ◽  
Predator Species ◽  
Naturally Occurring ◽  
Orius Majusculus ◽  
Limited Effectiveness ◽  
North Eastern ◽  
Predation Capacity ◽  
The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a recent issue for winegrowers in Southern Europe, in particular in North-eastern Italy. Problems are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the response by naturally occurring predators and parasitoids to E. vulnerata populations in vineyards is often unable to keep leafhopper densities under levels that are acceptable for winegrowers. Here we evaluated the potential of two generalist predators, i.e., Chrysoperla carnea and Orius majusculus, in controlling E. vulnerata populations. Laboratory and semi-field experiments were carried out to evaluate both species' predation capacity on E. vulnerata nymphs. Then, predators were released in vineyards colonized by large E. vulnerata populations. Both predator species exhibited a remarkable voracity in the laboratory and significantly reduced leafhopper densities in semi-field experiments. Predator releases in vineyards reduced leafhopper densities by about 30%. Results obtained in laboratory, semi-field, and field experiments are discussed to implement these biocontrol agents' use in pest control tactics.

Addressing the effects of bottom trawling on benthic processes using experimental and field studies in the Baltic Sea

2020 ◽  
Author(s):  
Claudia Morys ◽  
Martin Jakobsson ◽  
Mattias Sköld ◽  
Pere Masqué ◽  
Volker Brüchert ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Field Experiments ◽  
Biogeochemical Cycling ◽  
Field Studies ◽  
The Baltic Sea ◽  
Bottom Trawling ◽  
Flux Measurements ◽  
The Baltic ◽  
Benthic Ecosystems ◽  
The Impact

<p>Bottom trawling is one of the most important anthropogenic disturbances affecting marine ecosystems and there has been increased attention to its impacts on seabed habitats as well as the structure and functioning of benthic ecosystems. The impact of bottom trawling is well-known with regard to benthic organisms. However, we still have a poor understanding of its effects on bentho-pelagic coupling and biogeochemical cycling in the sediment. In the Baltic Sea, the study area of the present investigation, there is a particular lack of data.<br>Here, we present new results from field experiments to quantify changes in sediment properties, macrofauna and biogeochemical cycling after the passage of a benthic dredge. To put the results in a broader context, a field survey was conducted in six areas of different commercial trawling intensities in the Bornholm Basin. Acoustic geophysical mapping, isotope profiling, functional categorization of macrofauna and sediment-water nutrient and oxygen flux measurements were used to evaluate the physical disturbance of the seabed. Preliminary results suggest a range of ecological, biogeochemical and physical impacts of trawling in the Baltic Sea, with implications for benthic ecosystem functioning.</p>

scholarly journals Quantifying predator dependence in the functional response of generalist predators

2016 ◽  
Author(s):  
Mark Novak ◽  
Christopher Wolf ◽  
Kyle Coblentz ◽  
Isaac Shepard
Keyword(s):  
Method Development ◽  
Field Experiments ◽  
Empirical Evaluation ◽  
Generalist Predators ◽  
Functional Responses ◽  
Predator Species ◽  
Ratio Dependence ◽  
Species Abundances ◽  
Ratio Dependent ◽  
Predator Dependence

AbstractA longstanding debate concerns whether functional responses are best described by prey-dependent versus ratio-dependent models. Theory suggests that ratio dependence can explain many food web patterns left unexplained by simple prey-dependent models. However, for logistical reasons, ratio dependence and predator dependence more generally have seen infrequent empirical evaluation and then only so in specialist predators, which are rare in nature. Here we develop an approach to simultaneously estimate the prey-specific attack rates and predator-specific interference rates of predators interacting with arbitrary numbers of prey and predator species. We apply the approach to field surveys and two field experiments involving two intertidal whelks and their full suite of potential prey. Our study provides strong evidence for the presence of weak predator dependence that is closer to being prey dependent than ratio dependent over manipulated and natural ranges of species abundances. It also indicates how, for generalist predators, even the qualitative nature of predator dependence can be prey-specific.Author contributionsCW contributed to method development, KC and IS performed the caging experiment, and MN conceived of the study, carried out the fieldwork and analyses, and wrote the manuscript.

Cursorial spiders retard initial aphid population growth at low densities in winter wheat

2008 ◽  
Vol 98 (3) ◽  
pp. 249-255 ◽  
Author(s):  
K. Birkhofer ◽  
E. Gavish-Regev ◽  
K. Endlweber ◽  
Y.D. Lubin ◽  
K. von Berg ◽  
...  
Keyword(s):  
Population Growth ◽  
Functional Groups ◽  
Arable Land ◽  
Aphid Population ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Molecular Technique ◽  
Predator Species ◽  
Web Building ◽  
The Impact

AbstractGeneralist predators contribute to pest suppression in agroecosystems. Spider communities, which form a substantial fraction of the generalist predator fauna in arable land, are characterized by two functional groups: web-building and cursorial (non-web-building) species. We investigated the relative impact of these two functional groups on a common pest (Sitobion avenae, Aphididae) in wheat by combining a molecular technique that revealed species-specific aphid consumption rates with a factorial field experiment that analyzed the impact, separately and together, of equal densities of these two spider functional groups on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment, but this effect was limited to the initial aphid-population growth period and low-to-intermediate aphid densities. The molecular analysis, which used aphid-specific primers to detect aphid DNA in predator species, detected the highest proportion of aphid-consuming individuals in two cursorial spiders: the foliage-dwelling Xysticus cristatus (Thomisidae) and the ground-active Pardosa palustris (Lycosidae). The results suggest that manipulating the community composition in favour of pest-consuming functional groups may be more important for improving biological control than fostering predator biodiversity per se. Agricultural management practices that specifically foster effective species or functional groups (e.g. mulching for cursorial spiders) should receive more attention in low-pesticide farming systems.

scholarly journals Impact of Sclerotinia Stem Rot on Yield of Canola

Plant Disease ◽  
2007 ◽  
Vol 91 (2) ◽  
pp. 191-194 ◽  
Author(s):  
L. E. del Río ◽  
C. A. Bradley ◽  
R. A. Henson ◽  
G. J. Endres ◽  
B. K. Hanson ◽  
...  
Keyword(s):  
North Dakota ◽  
Field Experiments ◽  
Disease Incidence ◽  
The United States ◽  
Stem Rot ◽  
Sclerotinia Stem Rot ◽  
Potential Yield ◽  
Naturally Occurring ◽  
The Cost ◽  
The Impact

Sclerotinia sclerotiorum is the causal agent of Sclerotinia stem rot (SSR) of canola (Brassica napus). In North Dakota, the leading canola producer in the United States, SSR is an endemic disease. In order to estimate the impact of this disease on canola yield, field experiments were conducted from 2000 to 2004 at several locations in North Dakota and Minnesota. Experimental plots were either inoculated with laboratory-produced ascospores or infected by naturally occurring inoculum in commercial fields. Applying fungicides at different concentrations and timings during the flowering period created epiphytotics of diverse intensities. Disease incidence was measured once prior to harvesting the crop on 50 to 100 plants per plot. Results of the study indicated that 0.5% of the potential yield (equivalent to 12.75 kg/ha) was lost for every unit percentage of SSR incidence (range of 0.18 to 0.96%). Considering the current cost of fungicide applications and the market value of this commodity, a 17% SSR incidence could cause losses similar to the cost of a fungicide application. Additional efforts are required to improve current levels of tolerance of canola plants to this pathogen.

scholarly journals Field experiments on social media

2021 ◽  
Author(s):  
Mohsen Mosleh ◽  
Gordon Pennycook ◽  
David Gertler Rand
Keyword(s):  
Social Media ◽  
Field Experiments ◽  
Field Studies ◽  
Media Content ◽  
Attitudes And Beliefs ◽  
Online Environment ◽  
Online Behavior ◽  
Practical Advice ◽  
Experimental Approaches ◽  
The Impact

Online behavioral data, such as digital traces from social media, have the potential to allow researchers an unprecedented new window into human behavior in ecologically valid everyday contexts. However, research using such data is often purely observational, limiting its ability to identify causal relationships. Here we review recent innovations in experimental approaches to studying online behavior, with a particular focus on research related to misinformation and political psychology. In hybrid lab-field studies, exposure to social media content can be randomized, and the impact on attitudes and beliefs measured using surveys; or exposure to treatments can be randomized within survey experiments, and their impact observed on subsequent online behavior. In field experiments conducted on social media, randomized treatments can be administered directly to users in the online environment - e.g. via social tie invitations, private messages, or public posts - without revealing that they are part of an experiment, and the impacts on subsequent online behavior observed. The strengths and weaknesses of each approach are discussed, along with practical advice and central ethical constraints on such studies.

scholarly journals The effect of Trichoderma on the growth and development of tomato and bean under greenhouse and field conditions

2018 ◽  
pp. 35-45
Author(s):  
Gwendolyn Ban ◽  
Shamsul Akanda ◽  
Macquin Maino
Keyword(s):  
Papua New Guinea ◽  
Field Experiments ◽  
New Guinea ◽  
Field Studies ◽  
Growth Patterns ◽  
Shoot Length ◽  
Plant Diseases ◽  
Fresh Weight ◽  
Potted Plants ◽  
Root And Shoot Length

Trichoderma's plant growth stimulating effect is well-recognized besides its well-known role as a biocontrol agent against plant diseases. Two greenhouse and field studies were conducted at the Papua New Guinea University of Technology (PNGUOT) to test the effects of Trichoderma harzianum on the growth of tomato and bean plants. Greenhouse potted plants were inoculated with three T. harzianum strains at 106 CFUmL-1, whereas, the field experiments were inoculated with T. harzianum strain LIPIMCO548 in rice bran at 0, 25, 50 and 75g/m2 soil. In the greenhouse experiments, Trichoderma inoculation increased the root and shoot length, and total fresh weight of bean plant up to 16.57, 20.79 and 21.37%, respectively over the un-inoculated control. For tomato plants, significantly higher (p ≤0.05, LSD) average root growth was observed when inoculated with T. harzianum strain CE262 over the control. On average, Trichoderma inoculation increased the root and shoot length, and the fresh weight up to 26.4, 9.6 and 18.8%, respectively over the control. Similar growth patterns were also observed in the field experiments. These results will be of immense value to vegetable growers in Papua New Guinea (PNG), especially to the intensive vegetable growing areas in the highland regions of the country.

scholarly journals Predicting the impact of outdoor vector control interventions on malaria transmission intensity from semi-field studies

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Adrian Denz ◽  
Margaret M. Njoroge ◽  
Mgeni M. Tambwe ◽  
Clara Champagne ◽  
Fredros Okumu ◽  
...  
Keyword(s):  
Vector Control ◽  
Malaria Transmission ◽  
Field Experiments ◽  
Field Studies ◽  
Vectorial Capacity ◽  
Personal Protection ◽  
Pull System ◽  
Host Seeking ◽  
Spatial Repellents ◽  
The Impact

Abstract Background Semi-field experiments with human landing catch (HLC) measure as the outcome are an important step in the development of novel vector control interventions against outdoor transmission of malaria since they provide good estimates of personal protection. However, it is often infeasible to determine whether the reduction in HLC counts is due to mosquito mortality or repellency, especially considering that spatial repellents based on volatile pyrethroids might induce both. Due to the vastly different impact of repellency and mortality on transmission, the community-level impact of spatial repellents can not be estimated from such semi-field experiments. Methods We present a new stochastic model that is able to estimate for any product inhibiting outdoor biting, its repelling effect versus its killing and disarming (preventing host-seeking until the next night) effects, based only on time-stratified HLC data from controlled semi-field experiments. For parameter inference, a Bayesian hierarchical model is used to account for nightly variation of semi-field experimental conditions. We estimate the impact of the products on the vectorial capacity of the given Anopheles species using an existing mathematical model. With this methodology, we analysed data from recent semi-field studies in Kenya and Tanzania on the impact of transfluthrin-treated eave ribbons, the odour-baited Suna trap and their combination (push–pull system) on HLC of Anopheles arabiensis in the peridomestic area. Results Complementing previous analyses of personal protection, we found that the transfluthrin-treated eave ribbons act mainly by killing or disarming mosquitoes. Depending on the actual ratio of disarming versus killing, the vectorial capacity of An. arabiensis is reduced by 41 to 96% at 70% coverage with the transfluthrin-treated eave ribbons and by 38 to 82% at the same coverage with the push–pull system, under the assumption of a similar impact on biting indoors compared to outdoors. Conclusions The results of this analysis of semi-field data suggest that transfluthrin-treated eave ribbons are a promising tool against malaria transmission by An. arabiensis in the peridomestic area, since they provide both personal and community protection. Our modelling framework can estimate the community-level impact of any tool intervening during the mosquito host-seeking state using data from only semi-field experiments with time-stratified HLC.

Field Experiments on Social Conflict

2005 ◽  
Vol 10 (1) ◽  
pp. 33-50 ◽  
Author(s):  
Dean Pruitt
Keyword(s):  
Observational Studies ◽  
Laboratory Experiments ◽  
Field Experiments ◽  
Social Conflict ◽  
Observational Methods ◽  
Long Term Effects ◽  
Naturally Occurring ◽  
The Impact ◽  
Strength Of Association

AbstractField experiments, in which the researcher manipulates one or more variables in a naturally occurring setting, have sometimes been used in studies of social conflict and should probably be used more often. They are more useful than observational studies for assessing the impact of novel conditions, establishing cause and effect, and reducing confounding. And they are more useful than laboratory experiments for examining long-term effects and those that involve strong passions, and for establishing external validity. However field experiments also have their limitations. Some variables cannot be practically or ethically manipulated and require the use of observational methods, which are also more useful for looking at the relationships among a large number of variables and for estimating the strength of association between variables. Furthermore, laboratory experiments allow more control of conditions and greater flexibility in designing manipulations. What this suggests is that all three methods have their value.

scholarly journals Field Experiments on Social Media

2021 ◽  
pp. 096372142110547
Author(s):  
Mohsen Mosleh ◽  
Gordon Pennycook ◽  
David G. Rand
Keyword(s):  
Social Media ◽  
Field Experiments ◽  
Field Studies ◽  
Media Content ◽  
Attitudes And Beliefs ◽  
Online Environment ◽  
Online Behavior ◽  
Practical Advice ◽  
Experimental Approaches ◽  
The Impact

Online behavioral data, such as digital traces from social media, have the potential to allow researchers an unprecedented new window into human behavior in ecologically valid everyday contexts. However, research using such data is often purely observational, which limits its usefulness for identifying causal relationships. Here we review recent innovations in experimental approaches to studying online behavior, with a particular focus on research related to misinformation and political psychology. In hybrid lab-field studies, exposure to social-media content can be randomized, and the impact on attitudes and beliefs can be measured using surveys, or exposure to treatments can be randomized within survey experiments, and their impact on subsequent online behavior can be observed. In field experiments conducted on social media, randomized treatments can be administered directly to users in the online environment (e.g., via social-tie invitations, private messages, or public posts) without revealing that they are part of an experiment, and the effects on subsequent online behavior can then be observed. The strengths and weaknesses of each approach are discussed, along with practical advice and central ethical constraints on such studies.

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