Parameter (<i>β</i>s) estimation of the best set of models predicting flight of <i>Pityophthorus juglandis</i> in response to ambient temperature (T), light intensity (L), wind speed (W), and barometric pressure (P) and some of their interactions.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s002" target="_blank">Appendix S2</a> for detailed model components.</p><p>Parameter (<i>β</i>s) estimation of the best set of models predicting flight of <i>Pityophthorus juglandis</i> in response to ambient temperature (T), light intensity (L), wind speed (W), and barometric pressure (P) and some of their interactions.</p

The Gaussian relationship (<i>Y</i> = <i>α</i>×<i>exp</i>(−(<i>X</i>−<i>X0</i>)²/2<i>b</i>)) between <i>Pityophthorus juglandis</i> catches and temperature (°C).

<p>(A) Female: <i>N</i> = 855, <i>F</i> = 63.38, <i>P</i><0.001, <i>α</i> = 6.23, <i>b</i> = 5.11, <i>X</i>₀ = 26.16, adj. <i>R</i>² = 0.89; (B) Male: <i>N</i> = 855, <i>F</i> = 28.87, <i>P</i><0.001, <i>α</i> = 4.37, <i>b</i> = 5.89, <i>X</i>₀ = 26.87, adj. <i>R</i>² = 0.79. Blue □: Outliers; Red ◯: Data points used to fit curves. These points were the greatest values of trap catches from each of the temperature classes <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945-Blackburn1" target="_blank">[28]</a>.</p

Daily <i>Pityophthorus juglandis</i> catches from 8 May to 17 September, 2012.

<p>(A) 0600–1000 h; (B) 1200–1600 h; (C) 1800–2200 h. Time intervals: 0600 h (2200 h of the previous day–0600 h the current day); 0800 h (0600–0800 h); 1000 h (0800–1000 h); 1200 h (1000–1200 h); 1400 h (1200–1400 h); 1600 h (1400–1600 h); 1800 (1600–1800 h); 2000 h (1800–2000 h); and 2200 h (2000–2200 h). Green arrow points to 3 September, 2012 when <i>P. juglandis</i> flight activity stopped between 2000 and 2200 h for the season. <i>N</i> = 133 days.</p

Environmental abiotic variables (mean + SE) at various time intervals of a day during the diurnal flight study of <i>Pityophthorus juglandis</i>.

<p>(A) Temperature; (B) Light intensity (B); (C) Wind speed; and (D) Air pressure. Time intervals: 0600 h (2200 h of the previous day–0600 h the current day); 0800 h (0600–0800 h); 1000 h (0800–1000 h); 1200 h (1000–1200 h); 1400 h (1200–1400 h); 1600 h (1400–1600 h); 1800 (1600–1800 h); 2000 h (1800–2000 h); and 2200 h (2000–2200 h). Different lower-case letters above bars denote significant difference between time points with each variable (<i>α</i> = 0.05). <i>N</i> = 134 days except for the time interval 0800 where <i>N</i> = 133 days.</p

Second-order interactions of abiotic factors on <i>Pityophthorus juglandis</i> trap catches.

<p>(A) Temperature and light intensity (male); (B) Temperature and barometric pressure (male); (C) Light intensity and barometric pressure (male); (D) Temperature and light intensity (female); (E) Temperature and barometric pressure (female); (F) Light intensity and barometric pressure (female); and (G) Temperature and wind speed (female).</p

Sum of <i>w_i</i> (an indicator of relative importance in the model) for variables (terms) from selection of models predicting flight of <i>Pityophthorus juglandis</i> in response to ambient temperature (T), light intensity (L), wind speed (W), and barometric pressure (P) and their interactions.

<p>A total of 94 models (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s002" target="_blank">Appendix S2</a>) were tested. <i>w_i</i> indicates the relative likelihood of the model <i>i</i> being the best model given the data. Computation and interpretation of statistics followed <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945-Burnham1" target="_blank">[29]</a>. Superscripted numbers in parentheses denote ranks of the sum of <i>w_i</i> across terms appeared the same number of times in the models. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s003" target="_blank">Appendix S3</a> (Female) and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s004" target="_blank">S4</a> (Male) for detailed statistics.</p><p>Sum of <i>w_i</i> (an indicator of relative importance in the model) for variables (terms) from selection of models predicting flight of <i>Pityophthorus juglandis</i> in response to ambient temperature (T), light intensity (L), wind speed (W), and barometric pressure (P) and their interactions.</p

Crepuscular Flight Activity of an Invasive Insect Governed by Interacting Abiotic Factors

<div><p>Seasonal and diurnal flight patterns of the invasive walnut twig beetle, <i>Pityophthorus juglandis</i>, were assessed between 2011 and 2014 in northern California, USA in the context of the effects of ambient temperature, light intensity, wind speed, and barometric pressure. <i>Pityophthorus juglandis</i> generally initiated flight in late January and continued until late November. This seasonal flight could be divided approximately into three phases (emergence: January–March; primary flight: May–July; and secondary flight: September–October). The seasonal flight response to the male-produced aggregation pheromone was consistently female-biased (mean of 58.9% females). Diurnal flight followed a bimodal pattern with a minor peak in mid-morning and a major peak at dusk (76.4% caught between 1800 and 2200 h). The primarily crepuscular flight activity had a Gaussian relationship with ambient temperature and barometric pressure but a negative exponential relationship with increasing light intensity and wind speed. A model selection procedure indicated that the four abiotic factors collectively and interactively governed <i>P. juglandis</i> diurnal flight. For both sexes, flight peaked under the following second-order interactions among the factors when: 1) temperature between was 25 and 30°C and light intensity was less than 2000 lux; 2) temperature was between 25 and 35°C and barometric pressure was between 752 and 762 mba (and declined otherwise); 3) barometric pressure was between 755 and 761 mba and light intensity was less than 2000 lux (and declined otherwise); and 4) temperature was ca. 30°C and wind speed was ca. 2 km/h. Thus, crepuscular flight activity of this insect can be best explained by the coincidence of moderately high temperature, low light intensity, moderate wind speed, and low to moderate barometric pressure. The new knowledge provides physical and temporal guidelines for the application of semiochemical-based control techniques as part of an IPM program for this invasive pest.</p></div

Effects of time interval of the day and <i>Pityophthorus juglandis</i> sex on <i>P. juglandis</i> catches (mean + SE).

<p>(A) Effect of time interval; (B) Effect of <i>P. juglandis</i> sex. Time intervals: 0600 h: 2200 h the previous day–0600 h the current day; 0800 h: 0600–0800 h; 1000 h: 0800–1000 h; 1200 h: 1000–1200 h; 1400 h: 1200–1400 h; 1600 h: 1400–1600 h; 1800: 1600–1800 h; 2000 h: 1800–2000 h; and 2200 h: 2000–2200 h. Different lower-case letters above bars denote significant difference between time intervals (A) or between <i>P. juglandis</i> sexes (B) at <i>α</i> = 0.05. <i>N</i>_{time interval} = 268 except the time interval 0800 when <i>N</i> = 266. <i>N</i>_sex = 1205 for both sexes. Means plotted in (B) represent catches per 2 h interval.</p

Weekly <i>Pityophthorus juglandis</i> total trap catches (A) and percentage of males in selected catches (B) from 29 August, 2011 to 2 June, 2014 in five Lindgren funnel traps.

<p>Hash marks along the x-axis denote the first day of each week. Percentages of males are presented for weeks when more than 50 <i>P. juglandis</i> were trapped. Inset in (A): rescaling of weekly <i>P. juglandis</i> catches from 29 August, 2011 to 31 December, 2012 to facilitate comparison of seasonal flight pattern with 2013 and 2014 when flight responses were higher.</p

Summary of statistics from model selection to identify the best sets of models that predicted flight of <i>Pityophthorus juglandis</i> in response to ambient temperature (T), light intensity (L), wind speed (W), and barometric pressure (P).

<p>Of all 94 formulated models (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s002" target="_blank">Appendix S2</a>), Models 25 and 44 were the best models (based on <i>w_i</i>>0.10) that predicted female flight activity, whereas Model 44 was the best model that predicted male flight activity. <i>QAIC</i>: Quasi-likelihood adjusted Akaike’s Information Criteria (<i>AIC</i>); the model with the minimum <i>QAIC</i> was considered the best model; <i>Δ_i</i> (<i> = QAIC_i</i>–<i>QAIC_min</i>): the plausibility that the fitted model is the best model given the data (the larger the <i>Δ_i</i>, the less plausible is the model); <i>w_i</i> indicates the relative likelihood of the model <i>i</i> being the best model given the data; <i>ER</i>: Evidence ratio, is the weight of the best model divided by the weight of the fitted model <i>j</i> (the closer the <i>ER</i> to 1 the better). Computation and interpretation of statistics followed <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945-Burnham1" target="_blank">[29]</a>. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s003" target="_blank">Appendix S3</a> (Female) and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105945#pone.0105945.s004" target="_blank">S4</a> (Male) for detailed statistics.</p><p>Summary of statistics from model selection to identify the best sets of models that predicted flight of <i>Pityophthorus juglandis</i> in response to ambient temperature (T), light intensity (L), wind speed (W), and barometric pressure (P).</p