Effective Attraction Radius Research Articles

Optimizing early detection strategies: defining the effective attraction radius of attractants for emerald ash borerAgrilus planipennisFairmaire

AbstractAdult emerald ash borers are attracted to green prism traps baited with the ash host volatile (3Z)‐hexenol and the sex pheromone of emerald ash borer (3Z)‐dodecen‐12‐olide [(3Z)‐lactone]. Quantifying the heretofore unknown range of attraction of such traps would help optimize deployment strategies for early detection.Examining trap captures of traps deployed in pairs at variable distances offers insight into the range of attraction. Recent work has shown the range of attraction can be estimated as half the intertrap distance at which trap catch begins to decrease, which should occur when proximate traps overlap their respective attractive ranges.We estimated these traps' attractive range for emerald ash borer using 98 baited dark green prism traps deployed in pairs, one trap per tree, in an urban park in Saint Paul, Minnesota, USA in summer 2020.We estimate attractive range by fitting a logistic model to trap catch data using Bayesian inferential methods and describe advantages thereof.The attractive range of these baited traps was estimated to be between 16 and 73 m, with a median of 28 m. We recommend that dark green prism traps baited with these semiochemicals be placed 25–35 m apart near high‐risk entry points.

Protecting avocado trees from ambrosia beetles by repellents and mass trapping (push–pull): experiments and simulations

The polyphagous shot hole borer (PSHB), Euwallacea fornicatus (Eichhoff), is an ambrosia beetle (Coleoptera: Curculionidae) infesting avocado branches Persea americana Mill. in North America, South Africa and Israel. Field experiments were conducted with attractive quercivorol traps and repellents on trees to develop push–pull control methods. PSHBs were collected over the summer from multiple-funnel traps baited with quercivorol in grids of low-, medium- and high-density traps to assess mass trapping interactions and capture trends. Mean catch/trap-week was higher on peripheral outer traps compared to the next inner ring of traps in grids. These ratios and grids were simulated to estimate the circular effective attraction radius (EARc) of multiple-funnel traps and compared to a previous relationship for sticky traps yielding EARc from release rate of quercivorol. The results indicate that multiple-funnel traps have smaller EARc in higher-density grids, likely due to interactions between traps. Tests with verbenone compared to methyl salicylate (MeSA) indicate both are repellents and no evidence for synergism. Dollops of verbenone–MeSA–SPLAT (5% each volatile) were applied monthly at 10- and 40-cm spacings along branched trunks of avocado trees, with release of volatiles declining exponentially over a month. These treatments caused a reduction in both numbers of aggregations/tree and attacks/aggregation to about half that of untreated control trees. Verbenone–MeSA–SPLAT dollops caused localized phytotoxicity on avocado bark, suggesting 8 cm2 plastic bag dispensers containing 0.25 g verbenone are preferred at 40-cm spacing. Push–pull should be done just before flight season to overwhelm natural attraction of single females initiating aggregations.

Semiochemicals Affecting Attraction of Ambrosia Beetle Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) to Quercivorol: Developing Push-Pull Control.

Euwallacea fornicatus (Eichhoff), the polyphagous shot hole borer (PSHB), is an ambrosia beetle infesting avocado Persea americana Mill. limbs in North America and Israel. We conducted field experiments with sticky traps in avocado orchards to develop push-pull semiochemical methods of managing PSHB. Traps baited with 10-fold increasing doses (0.01 to 100× or 1.26 µg to 12.6 mg/d) of attractant quercivorol were previously shown to increasingly capture female PSHB (males flightless). We converted trap catch of this relationship to a standardized effective attraction radius (EAR) that predicts capture power of baited-traps regardless of insect flight density. Earlier, piperitone and verbenone were shown to strongly inhibit attraction of PSHB to quercivorol-traps. We tested increasing numbers of 1× piperitone dispensers at 0.75-m distance surrounding a quercivorol-trap and found PSHB catch to decline exponentially. Increasing decadic doses (0.01 to 10×) of either verbenone or piperitone released at 1× quercivorol-traps caused a sigmoidal first-order kinetic-decay in catch. Verbenone (1×) placed at increasing distances (0, 0.25, 0.5, 1, and 2 m) from a 1× quercivorol-trap became increasingly ineffective in reducing catch of PSHB. We found no evidence that ethanol released from 7.5 to 480 mg/d affected attraction of PSHB, but Scobicia chevrieri (Villa and Villa) (Coleoptera: Bostrichidae) was increasingly attracted. Due to their relatively short-range (<0.5 m) inhibition of attractive sources, piperitone, and verbenone dispensers should be placed on avocado trunks where PSHB aggregations occur before the flight season.

Attraction of the Euwallacea sp. near fornicatus (Coleoptera: Curculionidae) to Quercivorol and to Infestations in Avocado.

The Euwallacea sp. near fornicatus (Euwallacea sp. 1 hereafter) feeds on many woody shrubs and trees and is a pest of avocado, Persea americana Mill., in several countries including Israel and the United States. Quercivorol baits are commercially available for Euwallacea sp. 1 females (males do not fly), but their attractive strength compared to other pheromones and potential for mass trapping are unknown. We used sticky traps baited with quercivorol released at 0.126 mg/d (1×) and at 0.01×, 0.1×, and 10× relative rates to obtain a dose-response curve of Euwallacea sp. 1 attraction. The curve fitted well a kinetic formation function of first order. Naturally infested limbs of living avocado trees had attraction rates equivalent to 1× quercivorol. An effective attraction radius (EAR) was calculated according to previous equations for each of the various baits (1× EAR = 1.18 m; 10× EAR = 2.00 m). A pole with six sticky traps spaced from 0.25-5.75 m in height had captures of Euwallacea sp. 1 yielding a mean flight height of 1.24 m with vertical flight distribution SD of 0.88 m (0.82-0.96 m, 95% CI). The SD with specific EAR was used to calculate EARc, two-dimensional EAR (1× EARc = 0.99 m; 10× EARc = 2.86 m), for comparison with other insect pheromone traps and for use in simulations. The simulation methods described previously were performed with combinations of 1-16 traps with 1-50 aggregations per 9-ha plot. The simulations indicate mass trapping with quercivorol could be effective if begun in spring before Euwallacea sp. 1 establishes competing sources of attraction.

Monitoring and mass-trapping methodologies using pheromones: the lesser date moth Batrachedra amydraula.

The lesser date moth (LDM) Batrachedra amydraula is a significant pest of date palm fruits. Previously, detection and monitoring of the pest was inaccurate due to high costs of sampling with lifting machines. We report a practical system for detection and monitoring of LDM based on pheromone traps and relevant models. Dose-response experiments with LDM pheromone traps indicated a 1 mg lure is optimal for monitoring. Delta traps with adhesive covering their entire inner surface gave the highest captures while trap colour was unimportant. Sampling pheromone traps throughout the night indicated male flight began at 1:00-2:00 and reached a peak 2 h before sunrise. Monitoring traps exposed all year long in Israel revealed three generations with different abundance. Trapping transects in a date plantation indicated interference from a monitoring trap became minimal at distances >27 m away. Inter-trap distances closer than this may lower efficiency of monitoring and mass trapping in control programs. Our estimate of the circular effective attraction radius (EARc) of a 1 mg delta trap for LDM (3.43 m) shows this bait is among the most attractive compared with baits for other insects. We developed encounter-rate equations with the pheromone trap EARc to model the interplay between population levels, trap density and captures that are useful for detection of invasive LDM and its control by mass trapping. The integrated methodologies are applicable to many pest species.

Detection and monitoring of pink bollworm moths and invasive insects using pheromone traps and encounter rate models

Summary The pink bollworm moth Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) is one of the most destructive pests in agriculture. An ongoing eradication program using a combination of sex pheromone monitoring and mating disruption, irradiated sterile moth releases, genetically modified Bt cotton and local insecticide applications have all but exterminated the pink bollworm from the south‐western USA and portions of northern Mexico. However, the continued threat of reinvasion from Mexico reinforces the need to improve pheromone‐based monitoring. Invasions from other parts of the world such as India, where resistance to single‐gene transgenic Bt cotton has evolved, further heightens the need for better monitoring strategies. The mean flight height and standard deviation (SD) of the vertical flight distribution of pink bollworm males were estimated from catches on transparent sticky cylinder traps baited with synthetic pheromone at several heights above‐ground. An effective attraction radius (EAR) of a standard pheromone lure was estimated from male moth catches on the pheromone‐baited sticky traps and many similar blank traps. The circular EARc was estimated from the spherical EAR and SD. The EAR of a pheromone lure for pink bollworm was 1·03 m, and the EARc was 2·61 m. The mean flight height of males was 0·82 m, and the vertical flight distribution SD was 0·26 m. A computer program simulated male moth movement and capture on various numbers of traps of EARc distributed over areas of 1–100 km2. The simulated catch results were comparable to predictions using the EARc with modified encounter rate equations of Royama and Rogers. The encounter rate equations were solved for initial populations of male moths in the regions, and Poisson statistics were used to calculate population confidence limits. Synthesis and applications. Encounter rate models and Poisson methods can be used to determine levels of pheromone trap densities that are likely to detect and estimate low population levels of resident or invasive pink bollworms and many other pest insect species.

Modeling and Regression Analysis of Semiochemical Dose–Response Curves of Insect Antennal Reception and Behavior

Dose-response curves of the effects of semiochemicals on neurophysiology and behavior are reported in many articles in insect chemical ecology. Most curves are shown in figures representing points connected by straight lines, in which the x-axis has order of magnitude increases in dosage vs. responses on the y-axis. The lack of regression curves indicates that the nature of the dose-response relationship is not well understood. Thus, a computer model was developed to simulate a flux of various numbers of pheromone molecules (10(3) to 5 × 10(6)) passing by 10(4) receptors distributed among 10(6) positions along an insect antenna. Each receptor was depolarized by at least one strike by a molecule, and subsequent strikes had no additional effect. The simulations showed that with an increase in pheromone release rate, the antennal response would increase in a convex fashion and not in a logarithmic relation as suggested previously. Non-linear regression showed that a family of kinetic formation functions fit the simulated data nearly perfectly (R(2) >0.999). This is reasonable because olfactory receptors have proteins that bind to the pheromone molecule and are expected to exhibit enzyme kinetics. Over 90 dose-response relationships reported in the literature of electroantennographic and behavioral bioassays in the laboratory and field were analyzed by the logarithmic and kinetic formation functions. This analysis showed that in 95% of the cases, the kinetic functions explained the relationships better than the logarithmic (mean of about 20% better). The kinetic curves become sigmoid when graphed on a log scale on the x-axis. Dose-catch relationships in the field are similar to dose-EAR (effective attraction radius, in which a spherical radius indicates the trapping effect of a lure) and the circular EARc in two dimensions used in mass trapping models. The use of kinetic formation functions for dose-response curves of attractants, and kinetic decay curves for inhibitors, will allow more accurate predictions of insect catch in monitoring and control programs.

Deriving Insect Population Characteristics from Trap Data

Setting up traps is a common way of establishing the presence of a species of insects and its population density. Deriving estimates of population density from trap data typically requires knowledge of the properties of the trap, e.g. active area, strength of attraction, as well as some properties of the population, e.g. diffusion rate, [2]. These parameters are seldom exactly known, [1], and also tend to vary in time, e.g. as a result of changing climatic conditions. We propose using a set of traps in such a configuration that they have different rate of trapping the insects. The properties of the traps and the characteristics of the population, including its density, are simultaneously estimated from the streams of captured insects in these traps. The basic model is an advection-diffusion equation where the traps are represented via suitable advection term defined on the active area of the trap. The values of the unknown parameters of the model are derived by solving an optimization problem. The robustness of the method is demonstrated by numerical simulations. [1] J A Byers, Active space of pheromone plume and its relationship to effective attraction radius in applied models , Journal of Chemical Ecology 34 (2008) 1134--1145 [2] S Petrovskii, D Bearup, D A Ahmed, R Blackshaw, Estimating insect population density from trap counts , Ecological Complexity 10 (2012) 69-- 82

Modelling female mating success during mass trapping and natural competitive attraction of searching males or females

AbstractSimulation models of insects encountering sex pheromone with or without mass trapping in which the searching sex is either male (moths and many insect species) or female (some true bugs, beetles, and flies) were developed. The searching sex moved as a correlated random walk, while the opposite sex remained stationary (calling) and released an attractive sex pheromone. The searching sex was caught when encountering a pheromone‐baited trap, and females mated when encountering a male. An encounter with pheromone was defined by the searcher's interception of a circle termed the effective attraction radius (EARc). Parameters of movement (speed and duration), initial numbers of calling sex and searching sex, number of traps, area, and EARc of traps and calling sex were varied individually to evaluate effects on the percentage of females mating. In the natural condition without traps, female mating success in both models was identical. Increasing the EARc of the calling sex caused diminishing increases in female mating success, suggesting that evolution of larger pheromone release and EARc is limited by increasing costs (production/sensitivity) relative to diminishing increases and benefits of mating encounters. With mass trapping, increasing the EARc of traps or density of traps caused similar declines in female mating in both models, but the female‐searching model predicted slightly lower mating success than the male‐searching model. Increasing the EARc of calling insects or the initial density of insects caused similar increases in female mating in both models, but again the female‐searching model had slightly lower mating success than the male‐searching model. The models have implications for mating lek formation and for understanding the variables affecting the success of mass trapping programs for insect pests with either male or female sex pheromones.

Effect of trap color and height on captures of blunt-nosed and sharp-nosed leafhoppers (Hemiptera: Cicadellidae) and non-target arthropods in cranberry bogs

A series of field experiments was conducted in cranberry bogs in 2006–2010 to determine adult attraction of the two most economically important leafhopper pests of cultivated Vaccinium spp. in the northeast USA, the blunt-nosed leafhopper, Limotettix vaccinii (Van Duzee), and the sharp-nosed leafhopper, Scaphytopius magdalensis (Provancher), to colored (yellow, green, red, blue, white, and clear) sticky traps. We also determined the effects of trap height on insect captures, evaluated trap color characteristics (i.e., reflectance spectra, and red, green, and blue RGB values) for maximizing leafhopper capture while minimizing beneficial arthropod capture, and correlated within-season adult leafhopper captures from traps with nymphal captures from sweep nets. Leafhopper species exhibited distinct preferences to particular colors differing in intensities along a spectrum of wavelengths and RGB values: green was the most attractive color to blunt-nosed leafhoppers, followed by red and yellow; while yellow was most attractive to sharp-nosed leafhoppers, followed by green and red. Attraction of leafhoppers to other colors was similar to clear. Most insect predators (e.g. lady beetles, hoverflies, and minute pirate bugs), parasitic wasps, and honey bees also exhibited preferences to particular trap color characteristics, whereas green lacewings and spiders did not. An effective attraction radius was calculated for each color of trap and species. Additionally, we measured mean ± SD of flight heights of several species and showed that more leafhoppers and hoverflies were captured on red and yellow traps placed 0.1 m above the canopy; while captures of lady beetles were highest on traps placed 0.5 m above the canopy. Numbers of adult leafhoppers on traps were largely uncorrelated with numbers of nymphs in sweep net samples, except for blunt-nosed leafhoppers captured on red traps which were positively correlated with sweep net counts. We discuss the potential of using colored sticky traps to monitor leafhopper populations in the context of their non-target species effects in cranberries.

Estimating Insect Flight Densities from Attractive Trap Catches and Flight Height Distributions

Methods and equations have not been developed previously to estimate insect flight densities, a key factor in decisions regarding trap and lure deployment in programs of monitoring, mass trapping, and mating disruption with semiochemicals. An equation to estimate densities of flying insects per hectare is presented that uses the standard deviation (SD) of the vertical flight distribution, trapping time, the trap's spherical effective radius (ER), catch at the mean flight height (as estimated from a best-fitting normal distribution with SD), and an estimated average flight speed. Data from previous reports were used to estimate flight densities with the equations. The same equations can use traps with pheromone lures or attractive colors with a measured effective attraction radius (EAR) instead of the ER. In practice, EAR is more useful than ER for flight density calculations since attractive traps catch higher numbers of insects and thus can measure lower populations more readily. Computer simulations in three dimensions with varying numbers of insects (density) and varying EAR were used to validate the equations for density estimates of insects in the field. Few studies have provided data to obtain EAR, SD, speed, and trapping time to estimate flight densities per hectare. However, the necessary parameters can be measured more precisely in future studies.

Analysis of Vertical Distributions and Effective Flight Layers of Insects: Three-Dimensional Simulation of Flying Insects and Catch at Trap Heights

The mean height and standard deviation (SD) of flight is estimated for over 100 insect species from their catches on several trap heights reported in the literature. The iterative equations for calculating mean height and SD are presented. The mean flight height for 95% of the studies varied from 0.17 to 5.40 m, and the SD from 0.12 to 3.83 m. The relationship between SD and mean flight height (X) was SD = 0.711X(-0.7849), n = 123, R(2) = 0.63. In addition, the vertical trap catches were fit to normal distributions and analyzed for skew and kurtosis. The SD was used to calculate an effective flight layer used in transforming the spherical effective attraction radius (EAR) of pheromone-baited traps into a circular EAR(c) for use in two-dimensional encounter rate models of mass trapping and mating disruption using semiochemicals. The EAR/EAR(c) also serves to reveal the attractive strength and efficacy of putative pheromone blends. To determine the reliability of mean flight height and SD calculations from field trapping data, simulations of flying insects in three dimensions (3D) were performed. The simulations used an algorithm that caused individuals to roam freely at random but such that the population distributed vertically according to a normal distribution of specified mean and SD. Within this 3D arena, spherical traps were placed at various heights to determine the effects on catch and SD. The results indicate that data from previous field studies, when analyzed by the iterative equations, should provide good estimates of the population mean height and SD of flight.

Modeling distributions of flying insects: Effective attraction radius of pheromone in two and three dimensions

The effective attraction radius (EAR) of an attractive pheromone-baited trap was defined as the radius of a passive “sticky” sphere that would intercept the same number of flying insects as the attractant. The EAR for a particular attractant and insect species in nature is easily determined by a catch ratio on attractive and passive (unbaited) traps, and the interception area of the passive trap. The spherical EAR can be transformed into a circular EAR c that is convenient to use in two-dimensional encounter rate models of mass trapping and mating disruption with semiochemicals to control insects. The EAR c equation requires an estimate of the effective thickness of the layer where the insect flies in search of mates and food/habitat. The standard deviation ( SD) of flight height of several insect species was determined from their catches on traps of increasing heights reported in the literature. The thickness of the effective flight layer ( F L ) was assumed to be SD · 2 · π , because the probability area equal to the height of the normal distribution, 1 / ( SD · 2 · π ) , times the F L is equal to the area under the normal curve. To test this assumption, 2000 simulated insects were allowed to fly in a three-dimensional correlated random walk in a 10-m thick layer where an algorithm caused them to redistribute according to a normal distribution with specified SD and mean at the midpoint of this layer. Under the same conditions, a spherical EAR was placed at the center of the 10-m layer and intercepted flying insects distributed normally for a set period. The number caught was equivalent to that caught in another simulation with a uniform flight density in a narrower layer equal to F L , thus verifying the equation to calculate F L . The EAR and F L were used to obtain a smaller EAR c for use in a two-dimensional model that caught an equivalent number of insects as that with EAR in three dimensions. This verifies that the F L estimation equation and EAR to EAR c conversion methods are appropriate.

Active Space of Pheromone Plume and its Relationship to Effective Attraction Radius in Applied Models

The release rate of a semiochemical lure that attracts flying insects has a specific effective attraction radius (EAR) that corresponds to the lure's orientation response strength. EAR is defined as the radius of a passive sphere that intercepts the same number of insects as a semiochemical-baited trap. It is estimated by calculating the ratio of trap catches in the field in baited and unbaited traps and the interception area of the unbaited trap. EAR serves as a standardized method for comparing the attractive strengths of lures that is independent of population density. In two-dimensional encounter rate models that are used to describe insect mass trapping and mating disruption, a circular EAR (EAR(c)) describes a key parameter that affects catch or influence by pheromone in the models. However, the spherical EAR, as measured in the field, should be transformed to an EAR(c) for appropriate predictions in such models. The EAR(c) is calculated as (pi/2EAR(2))/F (L), where F (L) is the effective thickness of the flight layer where the insect searches. F (L) was estimated from catches of insects (42 species in the orders Coleoptera, Lepidoptera, Diptera, Hemiptera, and Thysanoptera) on traps at various heights as reported in the literature. The EAR(c) was proposed further as a simple but equivalent alternative to simulations of highly complex active-space plumes with variable response surfaces that have proven exceedingly difficult to quantify in nature. This hypothesis was explored in simulations where flying insects, represented as coordinate points, moved about in a correlated random walk in an area that contained a pheromone plume, represented as a sector of active space composed of a capture probability surface of variable complexity. In this plume model, catch was monitored at a constant density of flying insects and then compared to simulations in which a circular EAR(c) was enlarged until an equivalent rate was caught. This demonstrated that there is a circular EAR(c), where all insects that enter are caught, which corresponds in catch effect to any plume. Thus, the EAR(c), based on the field-observed EAR, can be used in encounter rate models to develop effective control programs based on mass trapping and/or mating disruption.

Simulation of Mating Disruption and Mass Trapping with Competitive Attraction and Camouflage

Simulation models of mass trapping and mating disruption were developed based on correlated random walks (CRW) of flying male moths searching for females. Males encountered pheromone plumes, transformed into a circular probability surface represented as an effective attraction radius (EAR), from females and from dispensers with or without traps. In simulations, parameters of dispenser EAR and density, female EAR and density, female stationary periods, male density, and male orienting times in EAR of dispensers or females were varied, whereas the male CRW parameters (speed, turning angle, and step size) remained constant to evaluate effects on the percentages of females mating. When male orienting time was constant regardless of EAR, the models indicated no difference in mating disruption efficacy between either a higher density of dispensers with smaller EAR or a lower density of dispensers with a compensating larger EAR. However, when the orienting time was increased in proportion to dispenser EAR, fewer dispensers with larger EAR were more effective in reducing female mating than were more numerous ones with smaller EAR. When costs of pheromone are substantial, however, more numerous dispensers of smaller EAR would be more economical because dose-response curves in previous studies indicate release rate must increase exponentially to achieve a linear increase in EAR. The models are useful in understanding the variables affecting the success of insect control programs. More precise measurements of the above parameters in the field are needed before the models can precisely predict outcomes of mating disruption and mass trapping.

EFFECTS OF ATTRACTION RADIUS AND FLIGHT PATHS ON CATCH OF SCOLYTID BEETLES DISPERSING OUTWARD THROUGH RINGS OF PHEROMONE TRAPS

Results were analyzed from six previous studies in which marked bark and ambrosia beetles, Ips typographus, I. paraconfusus, and Trypodendron lineatum (Coleoptera: Scolytidae), were released at the center of concentric rings of pheromone traps. Assuming nearly straight flight paths, a “filtering” equation model predicts recapture percentages on several trap rings of specified radii, trap numbers, and effective attraction radius (EAR) of a pheromone trap. Equations were used to calculate recapture percentages on concentric trap rings as a function of increasing EAR and gave polynomial relationships for each ring with terms equal to the number of inner rings plus one. Results were confirmed by computer simulations. Filtering equations were iterated with increasing EAR values to find one that gave a recapture percentage for the innermost trap ring that matched the field results. The estimated EAR for a synthetic pheromone bait of I. typographus was similar in five tests (range 1.39–1.78 m), but in two other tests was larger (3.27 and 15.9 m). The EAR for pheromone of 75 male I. paraconfusus in ponderosa pine logs ranged from 0.35 to 34.5 m (mean of 4.7 m) and was generally larger for previously pheromone-responding beetles than for freshly emerged ones. For T. lineatum, the EAR of lineatin-baited traps at 100-m radius was 2.43 m. Recaptures of I. typographus were reasonably predicted by the estimated EARs in the filtering model. To obtain perfect fits, another model assumed the EAR could vary with ring radius (dispersal distance) and found that the EAR for I. typographus decreased with dispersal distance in four experiments, but increased or was variable in two others. However, in I. paraconfusus and T. lineatum, the EAR increased with dispersal distance. Simulations that varied combinations of the EAR and random angles of maximum turning (AMT) of beetles stepwise showed that a nearly straight flight path for I. typographus explained observed catches on trap rings best, while a higher AMT of 36° was better to explain catches of T. lineatum. Simulations show that catch per trap ring in relation to radial distance can be influenced by the beetle's AMT (still unobserved in the field). A conceptual model of dispersal and host selection in “aggressive” bark beetles with regard to pioneer and joiner colonization strategies is presented.

Sampling range, attraction range, and effective attraction radius: Estimates of trap efficiency and communication distance in coleopteran pheromone and host attractant systems1

AbstractThere is a need for information on communication distances in natural systems and the ranges of action of synthetic pheromone traps. The differences between sampling range (RS, time dependent ecological measure) and attraction range (RA, behavioural measure) are stressed and compared to the simple but artificial effective attraction radius concept (REA, mainly trap and bait dependent). To estimate such ranges defined theoretical concepts and proper analysis of data are needed.Quantitative estimates are rare in the literature but maximum RA for Lepidoptera (moths) may reach 200–400 m and the corresponding RS functions may be in the range 200–500 m. RS estimated from regression of recapture of marked Cyclas formicarius (Curculionidae) after 16 h of sampling was 390 m for a high dose (10 μg) and 94 m for a low dose (0.01 μg). RA for bark beetles (Scolytidae) estimated from regression analysis of trap interactions are in the range of 19–97 m, but have large confidence intervals due to the few data points available. Passive traps at 1–35 m distance from pheromone traps yield RA values based on log‐log regression values of between 17 and 34 m depending on pheromone release (10‐5 to 10‐2 g/h) for Ips typographus. Effective attraction radii's were estimated, both as simple point‐estimates and as means with confidence intervals. Minima and maximum estimates obtained for bark beetles were 0.2‐1 m for Tomicus piniperda, 0.6 m for T. minor, 0.3‐3 m for Ips typographus, 3–10 m for Pityogenes chalcographus and 0.2‐0.4 m for Scolytus (scolytus) triarmatus.It is concluded that RS and RA are of great basic and applied value but both difficult to estimate. REA lacks a direct relation to natural behaviour but is a useful index of trapping power and specificity.ZusammenfassungFangbereich, Anlockungsbereich und effektiver Anlockungsradius als Schätzgrößen für die Falleneffektivität und Kommunikationsdistanz bei Käferpheromonen und wirtsabhängigen AnlockungssystemenDie Reichweite natürlicher und synthetischer Pheromonquellen ist Gegenstand der vorliegenden Arbeit. Die Entfernung von der Falle, innerhalb der Insekten gefangen (RS, eine zeitabhängige Größe) bzw. angelockt werden (RA, eine verhaltensbezogene Größe) werden mit dem einfachen, aber abstrakten Konzept des Anlockungsradius (REA‐, nur von Köder und Falle abhängig) verglichen. Zur Bestimmung solcher Größen werden theoretische Modelle für eine Analyse des Datenmaterials benötigt.Verläßliche Literaturangaben sind selten, jedoch können bei Lepidopteren für maximal RA Entfernungen von 200 bis 400 m, für RS von 200 bis 500 m erreicht werden. Schätzungen von RA anhand gegenseitiger Beeinflussung von Fallen liegen bei Borkenkäfern (Scolytidae) zwischen 19 und 97 m, wobei die Konfidenzintervalle wegen ungenügenden Wiederholungen groß sind. Für Ips typographus ergeben Fänge passiver, unbeköderter Fallen in 1 bis 35 m Abstand von Pheromonfallen nach log‐log Regression Werte für RA zwischen 17 und 34 m, in Abhängigkeit von der Pheromonabgabe (10‐5 bis 10‐2 g/h). Nach Regressionsanalyse von Fallenfängen markierter Cylas formicarius (Curculionidae) wurde nach 16 h ein RS von 390 m für eine hohe (10 μg), und ein RS von 94 m für eine niedrige Dosis (0.01 μg) bestimmt. Die Größe von REA wurde als Punktschätzung und als Mittelwert mit Konfidenzintervall bestimmt. Es ergaben sich Schätzungen für Borkenkäfer von 0.4 bis 1 m für Tomicus piniperda, 0,6 m für T. minor, 0,3 bis 3 m für I. typographus, 3 bis 10 m für Pityogenes chalcographus und 0,2 bis 0,4 m für Scolytus (scolytus) triarmatus.Als Schlußfolgerung ergibt sich, daß RS und RA von grundlegender und praktischer Bedeutung sind, ihre Schätzung ist jedoch schwierig. REA hat keine direkte Beziehung zum natürlichen Verhalten, ist jedoch ein brauchbares Maß für die Anziehungskraft und Spezifität der Fälle.

Effective attraction radius

The catches of bark beetles (Coleoptera: Scolytidae) were compared between attractive traps releasing semiochemicals and passive traps (cylindrical sticky screens hung, at 10 heights of 0.7-11.5 m, on poles). A central attractive-trap pole was surrounded by three passive-trap poles spaced 50 or 100 m away at the apices of an equilateral triangle. The catches ofTomicus piniperda and other scolytid species on the attractive-trap pole baited with host monoterpenes, or the catches ofIps typographus attracted to synthetic pheromone, were compared to passive trap catches in a Scots pine forest or in a Norway spruce clear-cut, respectively. Information about flight height distributions of the above scolytid species, andHylurgops palliatus, Cryphalus abietis, Pityogenes chalcographus, P. quadridens, P. bidentatus, andTrypodendron domesticum were obtained on the passive and attractive trap poles. A new method is presented for determining the densities of flying insects based on the passive trap's dimensions and catch, duration of test, and speed of insect. Also, a novel concept, the effective attraction radius (EAR), is presented for comparing attractants of species, which is independent of insect density, locality, or duration of test. The EAR is obtained by the ratio of attractive and passive trap catches and the dimensions of the passive trap, and thus should correlate positively with the strength of the attractant and the distance of attraction. EARs are determined from catch data ofT. piniperda andI. typographus as well as from the data of previous investigations on the same or other bark beetles.