Population biology of small mammals in Pureora forest park .1. Carnivores (

Populations of four species of carnivores were sampled over the five years 1983-87 at Pureora Forest Park, by regular three- monthly Fenn trap index lines supplemented with occasional control campaigns by shooting and additional traps. Stoats were the most frequently collected (63 captures), followed by weasels (18), cats (15) and ferrets (13). Stoats ranged throughout the mosaic of forest types but especially the older exotic blocks, hunting rabbits, rats, possums and birds. The mean age of 55 stoats trapped was 15 months, and their maximum life span about 5 years. The age-specific mortality rate of first year stoats was about 0.76, and the proportion of older stoats (>1 year) declined from 52% of 21 killed in summer/autumn of 1983 to 27% of 22 killed in the same seasons of 1984-87. Weasels were collected mainly from habitats favouring mice, such as a young plantation and the road verges, and 40% of 15 non-empty weasel guts contained mice. Cats and ferrets hunted the native forest blocks where their main prey, rats and possums, were abundant. The body sizes and reproductive patterns of mustelids at Pureora were similar to those recorded in podocarp-broadleaf forests elsewhere in New Zealand.     

How varying pest and trap densities affect Tribolium castaneum capture in pheromone traps

The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is an important insect pest in food processing facilities. Pheromone trapping is frequently used to monitor red flour beetle populations in structures; however, the optimal trap density and the relationship between trap captures and beetle density is not known. Two experiments were performed concurrently in environmentally controlled 30‐m² walk‐in chambers to determine the relationship between aggregation pheromone trap captures of red flour beetles and beetle and trap number. In one experiment, beetle density was kept constant at 200 individuals per chamber while trap number was varied from 1 to 8, and in the other experiment trap number remained constant at one per chamber while beetle density varied from 20 to 800 individuals. Results indicated that approximately one out of 23 red flour beetles were captured in a trap. Number of beetles captured in traps increased significantly as beetle density increased; however, the proportion of beetles captured remained consistent across beetle densities with a mean of 4.7 ± 0.6% of individuals captured. Trap captures varied significantly with trap placement within experimental chambers, indicating that subtle differences in the trapping environment can influence trap captures. Data suggested that trap densities of 0.07–0.10 m^?2 (2–3 traps per chamber) would maximize trap capture, whereas a trap density of 0.13 m^?2 (four traps per chamber) would maximize the predictive ability of a trapping equation estimating beetle density from trap captures. Results provide information needed to more thoroughly explore how environmental factors might influence red flour beetle trap capture in the absence of changes in beetle density. Further understanding of these relationships will allow for more accurate assessments of absolute beetle density from pheromone trap capture data.     

Large‐scale pest control in New Zealand beech forests

In 2014, baits laced with the poison sodium fluoroacetate (1080) were sown over 694 000 ha of mostly native beech forests in New Zealand to control rats, stoats and possums – a landscape‐scale pest control programme called ‘Battle for our Birds’. This large pest control operation was necessitated by the mast seeding of beech trees which led to irruptions of rodent and stoats which were predicted to lead to decreases in vulnerable native wildlife. In this article, we describe why and how this extensive pest control programme was developed and implemented. We describe the seedfall monitoring that was used to determine the need for large‐scale rodent and stoat control and the response of these predators to this control. We also provide a summary of the bird monitoring that was undertaken to demonstrate the effectiveness or otherwise of the programme.     

Improving predator capture rates: analysis of river margin trap site data in the Waitaki Basin, New Zealand

We recorded trap site characteristics and captures during a trapping programme designed to protect breeding and released black stilts (kaki, Himantopus novaezelandiae) from predation, in order to learn about trap site features that might improve the efficacy of future predator trapping management. Captures were made at 1629 leg-hold traps opened over 71 333 trap nights between 1998 and 2000, at six locations in the Upper Waitaki Basin, New Zealand. Twelve trap site variables were recorded. The model describing the best combination of variables for four groups of predators (cats Felis catus, mustelids Mustela furo (ferrets) and M. erminea (stoats), harriers Circus approximans and hedgehogs Erinaceus europaeus) was found using logistic regression and AIC values. For all predator groups both the way the trap was set and its placement within the landscape (with respect to habitat type and the distribution of landscape features that might be important to predators) influenced capture rates. Mustelids and harriers were more likely to be caught on stable riverbed habitats where rabbit densities are highest, while hedgehogs were mainly caught on river terraces and cats were equally likely to be caught anywhere. Individual trap characteristics in terms of set type, trap haze, trap backing, plate haze, visibility of bait, substrate and ground cover, associated with higher catch rates for each predator group are described.     

Mass trapping of Prays nephelomima (Lepidoptera: Yponomeutidae) in citrus orchards: optimizing trap design and density

The moth Prays nephelomima (Meirick) (Lepidoptera: Yponomeutidae) is a significant pest of citrus (Citrus spp.), and the recent identification of the female sex pheromone has enabled new direct control tactics to be considered. Six trap designs were compared for suitability in mass trapping, and Pherocon III delta traps were chosen to further evaluate mass trapping. A mass trapping field trial was carried out at five lemon, Citrus limon L., orchards to determine the effect of trap density on catch and rind spot damage on fruit. One plot (0.33-1.0 ha) of each of the five trap density treatments (3, 10, 30, 100, and 300 traps/ha) were operated at each orchard over 12 wk. Catch per trap was reduced as trap density increased and a mean of 12,000 and 16,000 males per ha were killed at the trap densities of 100 and 300 traps per ha, respectively. Increased trap density reduced the percentage of flowers infested with P. nephelomima larvae and reduced the number of moths emerging from flowers. The incidence of rindspot damage on fruit decreased from 45 to 16% as the density of traps increased from 3 to 100 traps per ha. Incidence (percentage of fruit with rindspot) and severity (number of rindspots per fruit) was similar at 100 and 300 traps per ha, indicating that the optimal trap density for reducing rindspot damage is likely to be between 30 and 100 traps per ha. Prospects for converting mass trapping to a lure and kill system are discussed.     

Sampling plan for the coffee leaf miner Leucoptera coffeella with sex pheromone traps

The population density of the coffee leaf miner Leucoptera coffeella (Guérin-Méneville & Perrottet) (Lep., Lyonetiidae) can be estimated using pheromone traps in coffee fields as male capture reflects this pest damage based on previous correlational study. However, the spatial distribution of pheromone traps and their density are necessary to optimize the sampling procedure with pheromone traps. Therefore, the objectives of the present study were to determine the pheromone trap density required per hectare to sample coffee leaf miner populations and to determine the spatial distribution of the males of this pest species. The males were sampled every 8 days in 12 consecutive evaluations. Taylor's power law and frequency distributions were used to recognize the distribution of the male capture data, which followed a negative binomial distribution. A common K was obtained, allowing the establishment of a single conventional sampling plan for the 12 fields investigated. The adjusted sampling plan requires eight traps in an area of 30 ha for a 25% precision error. Kriging-generated maps allowed the simulation of male captures for 8, 12 and 20 traps per 30 ha and the results were compared with those obtained with absolute sampling resulting in R ²-values of 0.30, 0.57 and 0.60 respectively. The traps were able to identify the more highly infested areas within the field and are a precise and efficient tool for sampling populations of L. coffeella.     

Comparison of trapping for eggs, females, and males of the naval orangeworm (Lepidoptera: Pyralidae) in almonds

The navel orangeworm is the primary insect pest of almonds in California, and egg traps are the primary means of monitoring this pest. A previous study found that the current use of 2-4 traps per 64 ha block usually is not sufficient to provide management information specifically for that block. In this study, we compare data from large grids of egg traps in varied commercial almond orchards with trapping data for females and males, with the objective of finding a more cost-effective monitoring program using currently available attractants. The proportion of egg traps with eggs was highly correlated with mean eggs per egg trap, and with females and males trapped simultaneously at the same location. Almond variety and the type of bait used had little impact on the relationship between the proportion of egg traps with eggs and the number of eggs per traps. Traps in orchards with more unharvested (mummy) almonds had more eggs, suggesting that navel orangeworm abundance affected traps more than competition from mummies. Laboratory experiments comparing age-specific oviposition in two-choice and no-choice situations found that younger, more fecund females laid a greater proportion of eggs on the preferred substrate in a two-choice situation, but that age-specific fecundity was not different between substrates in no-choice tests. These findings indicate that the proportion of egg traps with eggs provides a more stable indication of navel orangeworm phenology than mean eggs per trap. We suggest that similar information could be obtained in a more cost-effective manner with female trapping.     

Field experiments on the trapping of stoats (Mustela erminea)

Abstract

Steel Fenn traps spaced at 100 m, 200 m, 400 m, and 800 m intervals (total 88 traps) were set in the Eglinton and Hollyford valleys, Fiordland, New Zealand, for 14 days a month from November 1974 to March 1976. A total of 173 stoats were caught, mostly in the two summers. The number of stoats caught and the proportion of females did not change with trap spacing, but both were higher than in an earlier, informal trapping campaign in the same area (20 traps at 2.1 km average interval; 124 stoats caught). The capture rate on the experimental lines declined from 1.07 stoats per 100 trap-nights at the beginning of the average 14-day session to 0.42 at the end, a reduction of 60%. Immigration between trapping sessions probably occurred in all months, but was most marked in summer. The usefulness of the data for the formulation of management policies concerning stoats in the National Parks of New Zealand will be discussed, along with other relevant information, elsewhere.     

Responses of kukupa (

The kukupa or New Zealand pigeon (Hemiphaga novaeseelandiae) is gradually declining on the New Zealand mainland, due mostly to predation by introduced pest mammals including ship rats (Rattus rattus) and brushtail possums (Trichosurus vulpecula). We report on a co-operative project between Maori landowners, the Department of Conservation, and Manaaki Whenua–Landcare Research researchers to restore a Northland kukupa population and to examine kukupa nesting success in relation to pest abundance. Ship rats and possums were targeted by trapping and poisoning throughout Motatau Forest (350 ha) from 1997 to 1999; only possums were targeted in 2000. All 13 kukupa nests located before pest control started in late 1997 failed at the egg stage, but all seven nests located in 1998–99 successfully fledged young when trapping and tracking indices of possums and ship rats were less than 4%. After pest control, counts of kukupa and some other bird species increased at Motatau compared with counts in a nearby non-treatment block, suggesting numbers of adult kukupa can be increased in small forest areas by intensive pest control. This increase is due at least partly to increased nest success. Evidence from time-lapse video cameras, sign remaining at nests, and nest success rates under different pest control regimes suggest both ship rats and possums are important predators at kukupa nests.     

Quantifying Short-Term Foraging Movements in a Marsupial Pest to Improve Targeted Lethal Control and Disease Surveillance

In New Zealand, the introduced marsupial brushtail possum (Trichosurus vulpecula) is a pest species subject to control measures, primarily to limit its ability to transmit bovine tuberculosis (TB) to livestock and for conservation protection. To better define parameters for targeted possum control and TB surveillance, we here applied a novel approach to analyzing GPS data obtained from 44 possums fitted with radio-tracking collars, producing estimates of the animals’ short-term nocturnal foraging patterns based on 1-, 3- or 5-nights’ contiguous data. Studies were conducted within two semi-arid montane regions of New Zealand’s South Island High Country: these regions support low-density possum populations (<2 possums/ha) in which the animals’ home ranges are on average larger than in high-density populations in forested habitat. Possum foraging range width (FRW) estimates increased with increasing monitoring periods, from 150-200m based on a single night’s movement data to 300-400m based on 5 nights’ data. The largest average FRW estimates were recorded in winter and spring, and the smallest in summer. The results suggest that traps or poison-bait stations (for lethal control) or monitoring devices (for TB surveillance), set for > 3 consecutive nights at 150m interval spacings, would likely place >95% of the possums in this type of habitat at risk of encountering these devices, year-round. Modelling control efficacy against operational expenditure, based on these estimations, identified the relative cost-effectiveness of various strategies that could be applied to a typical aerial poisoning operation, to reduce the ongoing TB vectorial risk that possums pose in the High Country regions. These habitat-specific findings are likely to be more relevant than the conventional pest control and monitoring methodologies developed for possums in their more typical forested habitat.     

Effects of two pheromone trap densities against banana weevil, Cosmopolites sordidus, populations and their impact on plant damage in Uganda

Abstract:  An on-farm study to evaluate the effect of pheromone trap density on the population of the banana weevil, Cosmopolites sordidus (Germar) (Col., Curculionidae) was conducted in Masaka district, Uganda. The pheromone used was Cosmolure+, a commercially available weevil aggregation pheromone. Forty-two farms were assigned to one of three treatments: 0, 4 and 8 pheromone traps/ha. Pheromone lures were changed monthly at which time the traps were moved to a different location within the stand. Adult weevil population densities were estimated by using mark and recapture methodology at 0, 6, 12, 18 and 21 months, while damage to the banana corm was assessed at 0, 3, 6, 12, 18 and 21 months since the start of the experiment. Pheromone trap captures were generally low: about 10 weevils per trap per month. There were no significant differences in mean catches of C. sordidus per trap per month except for February 2002 when doubling the pheromone trap density decreased weevil catches. Although not significant, decreased efficiency was also the trend in higher trap densities over all the data sets. Doubling the number of traps increased the number of weevils caught per hectare per month from 0.4 to 0.6%. There was no significant difference in plant damage between the pheromone treatments in low- compared with high-trap densities. There were generally no significant differences in weevil populations and plant damage between pheromone-treated and control farms. Possible reasons for the low-trap efficacy in this study are discussed.     

Effectiveness of chain‐springs on leghold traps for reducing injuries to captured brushtail possums (Trichosurus vulpecula)

Abstract

Leghold traps continue to be an essential tool for managing brushtail possums (Trichosurus vulpecula) in New Zealand. Concerns about the injuries such traps cause have given rise to efforts to make these traps more humane. One trap modification that had potential for reducing injuries was the placement of an appropriately sized spring between two links of a trap chain to provide a cushioning effect when the chain is extended. Such springs were added to Lanes‐Ace and Victor No. 1½ traps and the injuries caused to captured possums were compared with those to possums captured in the same traps without springs or in Victor No. 1 traps. The addition of chain‐springs reduced the severity of injuries significantly, but injury scores were still significantly higher than for possums captured in Victor No. 1 traps. Consequently, although chain‐springs improved the welfare performance of the Lanes‐Ace and Victor No. 1½ traps, they did not do so to such an extent that those traps could be considered as humane as the currently acceptable Victor No. 1 traps.     

Can Mass Trapping Reduce Thrips Damage and Is It Economically Viable? Management of the Western Flower Thrips in Strawberry

The western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a cosmopolitan, polyphagous insect pest that causes bronzing to fruit of strawberry (Fragaria x ananassa). The main aim of this study was to test whether mass trapping could reduce damage and to predict whether this approach would be economically viable. In semi-protected strawberry crops, mass trapping of F. occidentalis using blue sticky roller traps reduced adult thrips numbers per flower by 61% and fruit bronzing by 55%. The addition of the F. occidentalis aggregation pheromone, neryl (S)-2-methylbutanoate, to the traps doubled the trap catch, reduced adult thrips numbers per flower by 73% and fruit bronzing by 68%. The factors affecting trapping efficiency through the season are discussed. Damage that would result in downgrading of fruit to a cheaper price occurred when bronzing affected about 10% of the red fruit surface. Cost-benefit analysis using this threshold showed that mass trapping of thrips using blue sticky roller traps can be cost-effective in high-value crops. The addition of blue sticky roller traps to an integrated pest management programme maintained thrips numbers below the damage threshold and increased grower returns by a conservative estimate of £2.2k per hectare. Further work is required to develop the F. occidentalis aggregation pheromone for mass trapping and to determine the best timing for trap deployment. Mass trapping of thrips is likely to be cost-effective in other countries and other high-value crops affected by F. occidentalis damage, such as cucumber and cut flowers.     

Trapping tunnel design incorporating behavioural preferences of stoats

Abstract

Stoats (Mustela erminea) are introduced pests in New Zealand, and there is an urgent need for effective trapping systems that kill the animal in a humane manner. A treadle trap was designed, the Dominus trap, that utilised an earlier‐proven humane killing system enhanced by the addition of a treadle plate trigger. This system enabled the trap to be classified as a Class A trap under the National Animal Welfare Advisory Committee (NAWAC) guidelines for animal kill traps, by successfully rendering 10/10 animals unconscious within 30 s. The Dominus trap mimics a tunnel, which by its very shape entices the animal to enter, but weighs only 600 g. Atrial at Flea Bay, on Banks Peninsula, used 35 Dominus traps placed alternately between 35 Fenn Mk VI traps set over 3150 trap nights (TN). The trial was conducted from March to May 2007 and was repeated for a further 7740 trap nights from January to March 2008, using 20 Dominus traps. The Dominus trap caught stoats consistently at the rate of 0.22 stoats/100 TN in both years, compared with 0 and 0.14/100 TN in Fenn traps, so potentially provides a humane alternative to the Fenn.     

Optimizing spatial positioning of traps in the context of integrated pest management

Agricultural research often relies on methods and approaches to represent and explain complex agro-ecosystems processes. In the context of biological control, auto dissemination strategies have been widely embraced for the management of various pests. One such strategy is using traps that attract arthropods into the hub of fungal based entomopathogens. The trapped pests are infected with the entomopathogen, which can then disseminate it among its conspecifics after being released. Despite the potential of the technique, its adoption especially by smallholder farmers has been limited, most likely due to the lack of an efficient trap positioning strategy. In this study, we propose an approach to improve the field application of fungal-based bio-pesticides (entomopathogenic fungi or EPF) by optimizing the spatial distribution of traps. The optimal field distribution of traps can be determined based on the following steps: (i) a field experiment to assess the dispersal ability of the pest infected by an entomopathogenic fungi (EPF) and (ii) the model-based estimation of the optimum traps density and distribution per unit of space (ha, km²). Based on experimental data we applied nonlinear regression and spatial optimization processes to calculate the radius covered by one trap and to estimate the optimum number and spatial positioning of the traps. We applied the method to a case study using the fungal isolate ICIPE 62 to control the invasive fruit fly Bactrocera dorsalis. The research revealed that nine pheromone traps per ha are required with a spacing distance of 37.45 m between the traps. The proposed approach can also be applied to other pest species, to help farmers reduce the number of traps used on a farm and to assist researchers and policymakers to optimize auto dissemination strategies in the context of integrated pest management (IPM).     

Abundance of wasps and prey consumption of paper wasps (Hymenoptera, Vespidae : Polistinae) in Northland, New Zealand

Polistine and vespine wasps were captured in Malaise traps in two fire-modified shrubland habitats of varying canopy height and composition at Lake Ohia, Northland, New Zealand. Prey consumption rates were calculated for the Asian paper wasp (Polistes chinensis antennalis) occupying these two areas of shrubland and a home garden in Whangarei, Northland. The sites were systematically searched for nests and wasp prey determined by intercepting foragers returning to nests. The Asian paper wasp predominated in the Malaise trap samples from the low- growing habitat while the German wasp (Vespula germanica) was more common in the taller vegetation type. The Asian paper wasp was more abundant than the German wasp in the samples in February and early March. Only four Australian paper wasps (Polistes humilis) and no common wasps (Vespula vulgaris) were caught. Asian paper wasps collected an estimated 15 000 prey loads per ha per season from one of the shrubland areas, and 478 000 prey loads per ha per season from the second area. These convert to estimates of 31 and 957 g per ha per season of invertebrate biomass removed by paper wasps from each habitat, respectively. The estimate for the garden site was 79 g per ha per season. Wasp nest densities varied between 20 and 210 nests per hectare. The biomass estimates are similar to average figures calculated for vespine wasps in scrubland and pasture. Both Asian paper wasps and Australian paper wasps preyed mainly on lepidopteran larvae. The cabbage white butterfly (Pieris rapae) was the most commonly collected species. Noctuid species were also well represented. Both male and female Asian paper wasps collected nectar in late March and early April.     

Understanding home range behaviour and resource selection of invasive common brushtail possums (Trichosurus vulpecula) in urban environments

Because invasive species are often opportunistic and behaviourally flexible, they tend to be successful in urban landscapes, where they may use space differently than in their more traditional habitats. Consequently, control strategies developed for invasive pest species in non-urban areas may not succeed in an urban context. Using GPS tracking, we examined habitat use by an invasive pest, the brushtail possum (Trichosurus vulpecula) in residential New Zealand habitats; these habitats comprise a large proportion of the urban landscape and are currently not targeted for pest control. We predicted that home ranges of possums in residential areas would be larger than those in non-urban habitats due to lower densities of their primary food resource, plant material; that possums would prefer forest fragment habitat; and that they would avoid roads due to the mortality risk. Home range sizes estimated using mechanistic Brownian bridges and 100 % minimum convex polygons were smaller or similar in size to those recorded in rural and forest habitats. Resource utilization functions and the regression of utilization distribution probabilities against environmental variables showed that possums selected forest fragments primarily, followed by residential habitat characterised by large gardens with a degree of vegetative structural complexity. Roads were not avoided. Control operations should expand their scope to include residential areas containing mature, diverse vegetation rather than only focussing on forest fragments, a strategy that ignores biodiversity values in residential habitats, and is likely to be unsuccessful due to reinvasion potential from neighbouring residential areas.     

A Single-Sampling Hair Trap for Mesocarnivores

Abstract Although techniques to analyze and quantify DNA-based data have progressed, methods to noninvasively collect samples lag behind. Samples are generally collected from devices that permit coincident sampling of multiple individuals. Because of cross-contamination, substantive genotyping errors can arise. We developed a cost-effective (US$4.60/trap) single-capture hair trap for American martens (Martes americana). In the field, traps effectively targeted martens; >75% of all hair samples were identified as marten. Eighty percent of marten hair (n = 180) contained sufficient quality for DNA-based analyses. This effective and affordable trap can be used by managers to monitor mesocarnivore populations noninvasively.     

Female sex pheromone of brinjal fruit and shoot borer,Leucinodes orbonalis (Lepidoptera: Pyralidae): trap optimization and application in IPM trials

Delta and wing traps baited with synthetic female sex pheromone of Leucinodes orbonalis Guenée were found to catch and retain ten times more moths than either Spodoptera or uni-trap designs. Locally-produced water and funnel traps were as effective as delta traps, although 'windows' cut in the side panels of delta traps significantly increased trap catch from 0.4 to 2.3 moths per trap per night. Trap catch was found to be proportional to the radius of sticky disc traps in the range 5-20 cm radius, discs with a 2.5 cm radius caught no moths. Wing traps placed at crop height caught significantly more moths than traps placed 0.5 m above or below the crop canopy. Replicated integrated pest management (IPM) trials (3 x 0.5 ha per treatment) were conducted in farmers fields with young and mature eggplant crops. Farmers applied insecticides at least three times a week in all check and IPM plots. In addition pheromone traps were placed out at a density of 100 per ha and infested shoots removed weekly in the 0.5 ha IPM plots. Pheromone trap catches were reduced significantly from 2.0 to 0.4 moths per trap per night respectively in check and IPM plots in a young crop and 1.1 to 0.3 moths per trap per night in check and IPM plots respectively in a mature crop. Fruit damage was significantly reduced from an average of 41.8% and 51.2% in check plots of young and mature crops respectively to 22% and 26.4 respectively in the associated IPM plots. Significant differences in pheromone trap catches and fruit damage were attained four and two weeks respectively after IPM treatments began in the mature crop whereas in the immature crop significant differences were not observed for the first eight to nine weeks respectively. The relative impact of removing infested shoots and mass trapping on L. orbonalis larval populations was not established in these trials but in both cases there was an estimated increase of approximately 50% in marketable fruit obtained by the combination of control techniques compared to insecticide treatment alone.     

Comparison of mating disruption and mass trapping with Pyralidae and Sesiidae moths

Mating disruption and mass trapping for control of lepidopteran pests use synthetic sex pheromone to prevent males from finding and mating with females. Here, we identify the behavioral mechanism underlying mating disruption and mass trapping of American plum borer, Euzophera semifuneralis (Walker) (Lepidoptera: Pyralidae), peachtree borer, Synanthedon exitiosa Say, and lesser peachtree borer, Synanthedon pictipes (Groeten) (Lepidoptera: Sesiidae). In addition, we derive relative dispenser activity (Relative D_a) from the competitive attraction equation to compare the disruptive activity of the devices used in mating disruption and mass trapping. Dispensers and traps were deployed in replicated 0.14‐ha cherry or peach plots with E. semifuneralis or the Synanthedon moths, respectively. Dispenser densities were 0, 10, 20, 59, 185, and 371 per ha, whereas trap densities were 0, 10, 20, 40, 79, and 158 per ha. Moth catch in a centrally placed, pheromone‐baited monitoring trap in each plot was used to evaluate the treatments. The profile of moth captures in mating disruption and mass trapping with the three species indicates that competitive attraction is the behavioral mechanism responsible for trap disruption. Relative D_a is 0.27, 0.23, and 0.53 with American plum borer, peachtree borer, and lesser peachtree borer, respectively, which indicates that the traps are 1.9–4.4 times more effective in reducing moth catch than the dispensers. Relative D_a can be used to compare devices for pheromone‐based behavioral manipulation of these and other species that are competitively attracted to artificial pheromone sources. When the same type of trap is employed for monitoring and mass trapping, Relative D_a is the same as dispenser activity D_a.