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Author

Daniel Emmen

Other affiliations: Pennsylvania State University
Bio: Daniel Emmen is an academic researcher from University of Panama. The author has contributed to research in topics: Panama & Aphid. The author has an hindex of 3, co-authored 8 publications receiving 23 citations. Previous affiliations of Daniel Emmen include Pennsylvania State University.

Papers
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Journal ArticleDOI
TL;DR: An edge-biased colonization process, initiated by females for at least the second growth cycle in the northeastern United States, followed by density-dependent movement away from crowded areas of declining host quality is hypothesized.
Abstract: We describe the dynamics of potato leafhopper, Empoasca fabae (Harris) (Homoptera: Cicadellidae), populations in a 4-ha alfalfa field over 2 yr. Population growth and spatial structure were strongly influenced by days after cutting. Capture of E. fabae by suction traps above the boundary layer along with sex ratios of in-field populations suggested that immigrants contributed to population growth throughout the second and third alfalfa growth cycles. Initial sex ratios were strongly female biased (1995, 80%; 1996, 90%), with the degree of bias decreasing and approaching a 1:1 ratio through the third growth cycles. A higher proportion of the population was located in the edge relative to the interior plots in three of four alfalfa growth cycles. Spatial correlation between females and males was initially low, but increased as density increased; this correlation also decreased immediately after alfalfa harvest, and significantly increased over time after harvest. These data suggest that dynamic in-field spatial organization exists for E. fabae. Although the entire field was colonized, we hypothesize an edge-biased colonization process, initiated by females for at least the second growth cycle in the northeastern United States, followed by density-dependent movement away from crowded areas of declining host quality.

15 citations

Journal ArticleDOI
TL;DR: Assays of extracts composed of low molecular weight metabolites from 28 species of plants from 15 families from Panamanian forest showed variation in toxicity to A. craccivora, hence, the activity probably was due to the toxic proteins, rather than contaminating toxic metabolites.
Abstract: Although aphids remain serious pests, bioassay-guided purification of anti-aphid compounds depends upon assays that are laborious and often have incomplete descriptions of methods. We provide the protocol for a rapid, efficient assay using a 96-well microtiter plate format for testing extracts for activity against the cotton aphid, Aphis gossypii Glover (Sternorrhyncha: Aphididae), and the black bean aphid, Aphis craccivora Koch. Assays of extracts composed of low molecular weight metabolites from 28 species of plants from 15 families from Panamanian forest showed variation in toxicity to A. craccivora. Three metabolite extracts and one protein extract were active, with more than 70% mortality in 72 h, averaged over three independent experiments. For three species of plants with protein extracts having intermediate activity, the metabolite extracts were inactive; hence, the activity probably was due to the toxic proteins, rather than contaminating toxic metabolites.

4 citations

Journal ArticleDOI
30 Apr 2020
TL;DR: A. oblongus is a new record for Panama and was collected in the town of Pirre, Province of Darien, and the pseudoscorpion was found attached to the coxa of the right hind leg of the fly.
Abstract: Some species of pseudoscorpions perform a mechanism known as phoresy, attach themselves to other organisms for transportation. In this work, Americhernes oblongus (Pseudoscorpiones: Chernetidae) is reported as a phoront on a species of fly belonging to the genus Scipopus (Diptera: Micropezidae). A. oblongus is a new record for Panama and was collected in the town of Pirre, Province of Darien. The pseudoscorpion was found attached to the coxa of the right hind leg of the fly. To our knowledge, there are no previous reports of phoresy between A. oblongus and Scipopus sp. as a dispersal method.

2 citations


Cited by
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Journal ArticleDOI
TL;DR: Correlations between these immigrants and end of season emigrants confirm that adults overwinter locally, and no clear explanation could be found in examining environment, plot exposure, migrations or other factors.

41 citations

Journal ArticleDOI
TL;DR: The knowledge to date on biology of the potato leafhopper, Empoasca fabae (Harris), including its distribution, development, migration, agricultural host plants, and mechanics of injury to host plants are summarized.
Abstract: This article summarizes the knowledge to date on biology of the potato leafhopper, Empoasca fabae (Harris), including its distribution, development, migration, agricultural host plants, and mechanics of injury to host plants. Damage to alfalfa, potatoes, soybeans, and snap beans, and treatment guidelines, are summarized. Particular attention is given to integrated pest management options in alfalfa, the host plant most frequently incurring economically damaging populations of potato leafhopper. Alfalfa scouting and economic thresholds are discussed along with cultural controls and host plant resistance.

25 citations

Journal ArticleDOI
TL;DR: An interaction between gender and sampling period was observed, the males showing a peak of infected individuals later in the season (35%) and some possible behavioral explanations of the data obtained are given.
Abstract: The differences between the seasonal occurrence and likelihood of being infected by FD phytoplasmas, of male and female Scaphoideus titanus Ball, were investigated. Sex ratio (male: female) was calculated by counting males and females sampled by means of yellow sticky traps and sweep-nets and from adults derived from hatched eggs in field-collected grapevine wood. PCR essays were performed to test differences in infection between genders. Overall, the sex ratio on sticky traps was significantly more male biased (1.99 : 1) if compared to net sweeping (0.62 : 1) and laboratory rearing (0.60 : 1). The peak of male presence was recorded in the middle of July in laboratory rearing and sweep net, and in the middle of August on sticky traps; the maximum presence of females was detected at the end of July in laboratory rearing, and at the end of August in sweep net samplings and on sticky traps. The seasonal sex ratio was more male biased at the beginning in laboratory rearing (1.50 : 1) and sticky traps (9 : 1), and then decreased in favor of females at the end of the sampling period, both in laboratory rearing (0.17 : 1) and in sticky traps (0.07 : 1). This trend was significantly less skewed, although similar, in sweep net samplings that recorded a sex ratio of 1 : 1 and 0.16 : 1 at the beginning and at the end of the sampling period, respectively. Concerning phytoplasma detection, an interaction between gender and sampling period was observed, the males showing a peak of infected individuals later in the season (35%). Some possible behavioral explanations of the data obtained are given.

21 citations

Journal ArticleDOI
TL;DR: The intra‐plot spatial distribution of the green leafhopper Empoasca vitis (Goethe) (Cicadellidae, Empoascini) was assessed over three successive growing seasons in a Bordeaux vineyard.
Abstract: 1 The intra-plot spatial distribution of the green leafhopper Empoasca vitis (Goethe) (Cicadellidae, Empoascini) was assessed over three successive growing seasons in a Bordeaux vineyard. Weekly measurements of adult trappings and nymphal counts were performed in a 1.7-ha plot on 130 sampling points. 2 Statistical and geostatistical analyses revealed inconsistent spatial distributions of adults and nymphs in spring, but consistent spatial distributions in summer, which were identical every year. 3 Similarities between spatial distributions of the mobile adults and the sedentary and aggregated nymphs strongly suggest that adults disperse inside the plot to areas preferred for egg deposition. 4 The similarity of summer populations among years suggests that this insects distribution is based on (perennial) differences in plot characteristics.

19 citations

DOI
21 May 2013
TL;DR: In this article, a trabajo tuvo por objetivo determinar the distribucion espacial de las poblaciones de trips in aguacate, a plaga causada by el hongo Elsinoe perseae.
Abstract: RESUMEN Mexico es el principal productor y exportador de aguacate en el mundo Los trips son con-siderados como una de las principales plagas del aguacate en Mexico, debido a su asociacion con la en-fermedad denominada rona del fruto, causada por el hongo Elsinoe perseae Esta enfermedad representa una fuerte limitante a la produccion del cultivo; el hongo penetra la fruta por las heridas causadas por el complejo de varias especies de trips El analisis del comportamiento espacial de esta plaga proporcionara informacion que contribuira a establecer estrategias de manejoadecuadas y dirigidas dentro de las huer-tas de aguacate Este trabajo tuvo por objetivo determinar la distribucion espacial de las poblaciones de trips en aguacate( Persea americana Mill) Cv Hass mediante el uso de tecnicas de estadistica espacial (Geoestadistica y SADIE) que condujeran en el caso de la Geoestadistica a la generacion de mapas por medio del krigeado Se logro determinar ademas, la estabilidad espacial y temporal a corto plazo de las poblaciones de trips Los resultados demostraron que las poblaciones de trips presentan una distribucion de tipo agregada, ajustandose a los modelos de tipo Esferico y Gaussiano Dicho comportamiento fue corroborado por los indices de SADIE y los mapas de densidad elaborados Los resultados demuestran que no existe una infestacion del 100% en las parcelas de estudio, lo cual resulta de gran interes para dirigir las medidas de control sobre areas especificas de infestacion y conseguir con ello posibles ahorros economicos y medioambientales

18 citations