Biological Control Potential and Drawbacks of Three Zoophytophagous Mirid Predators against Bemisia tabaci in the United States

Miridae (Hemiptera) of the tribe Dicyphini are important zoophytophagous predators use to control pest arthropods in vegetable crops. However, the risk that their herbivory may cause economic damage could hinder their application as useful biocontrol agents and may limit the likelihood they would meet regulatory requirements for importation. We conducted field cage studies to assess the predation capacity and tomato plant damage of three mirid species established in south USA, a known biocontrol agent (Nesidiocoris tenuis), and two native species (Macrolophus praeclarus and Engytatus modestus). All three species significantly reduced the number of whiteflies (Bemisia tabaci) on tomato plants compared to tomato plants without mirids. More damage, evaluated as the number of necrotic rings, was observed on tomato plants with E. modestus and N. tenuis compared to M. praeclarus. In our experiments that included sesame plants (Sesamum indicum) with tomato plants, mirid numbers increased despite a low number of prey, thus showing a benefit of the plant-feeding habit of these predators. USA’s established mirids may therefore prove to be immediately available biological agents for the management of present and future tomato pests

Advancing employee engagement theory : a re-examination of the psychological conditions and antecedents of engagement

The engagement of employees has been a 'hot topic' among business and organizational behaviour researchers, consultants and human resource practitioners in recent years. Engagement is a motivational concept. In this study employee engagement (or job engagement) has been defined as an employee's full investment of oneself in one's work activities. The study nevertheless accepts that the field of engagement has been plagued with numerous terms, definitions, measures and theories. Although engagement research originated in the early 1990s, there is today a lack of consensus and consistency about important conceptual issues, such as definition and dimensionality. The current scholarly work sought to bring some clarity to the field by firstly recognising two broad streams for which the conceptualizing, theorising and operationalizing of engagement have differed markedly. The self-investment and anti-burnout engagement streams were named. Next, a domain for research focus was selected. The self-investment engagement stream, which offers the most unique, objective and encompassing meaning and theory of engagement, was identified. This stream recognises Kahn's 1990 work as the foundation of engagement study. The conceptualization of engagement as the full-investment of oneself, physically, cognitively and emotionally in one's work has been derived from this early contribution. The theory of engagement found within the self-investment stream, proposes that several antecedents influence three psychological conditions, which in turn predict engagement. in the current study, task-relevant job resources, socially relevant job resources and job demand characteristic were incorporated in the theoretical framework for evaluation. The job characteristic antecedents are task significance, skill variety, autonomy, feedback, internal interaction, work overload, friendship opportunity and managerial support. The psychological conditions of engagement are known as psychological meaningfulness, availability and safety. The study's results have supported the hypotheses that task significance and internal interaction are direct predictors of meaningfulness; autonomy, feedback, internal interaction and work overload are predictors of psychological availability; while, friendship opportunity and managerial support are significantly associated with psychological safety. The three psychological conditions were positively associated with engagement. It was found that psychological meaningfulness mediated the associations between the other two conditions and engagement. Then, skill variety showed a direct positive association with engagement, rather than an indirect association via one of the psychological conditions

The dates and number of giant African snails collected from 22 locations (cores) located in Miami Dade County, Florida, USA.

<p>The dates and number of giant African snails collected from 22 locations (cores) located in Miami Dade County, Florida, USA.</p

Relationship between the size of gravid giant African snails and the number of eggs produced per snail.

<p>Dots: Observed values. Full line: Predicted relationship. Broken lines: 95% confidence limits.</p

Percent of gravid snails occurring in Core1 and 2 each week from 25 March 2012 through 30 March 2014 plotted against the maximum weekly temperature (dots).

<p>The heavy full line shows the predicted relationship based on logistic regression with 95% confidence limits (broken lines).</p

Relationship between the size of giant African snails and (A) the percentage of reproductive snails, (B) the number of eggs per reproductive snail, and (C) the distributions of snails (left axis) and eggs (right axis) per size class.

<p>Data are grouped in size classes of 5 mm. Dots and vertical lines: Observed values with 95% confidence limits for the mean (for points where <i>n ></i> 1). Full and broken lines: predicted values with 95% confidence limits. Bars: Percentage of all snails (red) and reproductive snails (blue) in size class <i>S</i>.</p

Population dynamics of giant African snails collected from 22 populations (cores) located in South Florida, U.S.A. from 25 March, 2012–30 March 2014.

<p><b>A</b>: Number of snails (filled circles: all individuals; open circles: gravid individuals). <b>B</b>: Average shell size. <b>C:</b> Percentage of gravid snails. <b>D</b>: Average number of eggs per snail. Thin vertical lines show 95% confidence limits for mean values (only when <i>n</i> > 1). Trend lines with 95% confidence limits are shown.</p

Populations (cores) of Giant African Snail located in Miami-Dade County, Florida USA, studied from March 29, 2012 through April 1, 2014.

<p>Populations (cores) of Giant African Snail located in Miami-Dade County, Florida USA, studied from March 29, 2012 through April 1, 2014.</p

Factors affecting the abundance of snails from 25 March 2012 through 30 March 2014.

<p>A. Number of giant African snails (≥ 45 mm) in Core 1 and 2. B. Number of Giant African Snails (≥ 45 mm) in Core 4, 5, 10 and 12. Trend lines for the periods where snails were controlled by means of standard (full bold line) or metaldehyde (broken bold line) treatments are shown. The arrows mark the change from standard to metaldehyde treatments. Thin lines show the predicted number of snails using treatment, time and the average daily humidity (<i>mHumAvg</i>) for each week as predictor variables (Core 1 and 2 only).</p