Pest Consumption Research Articles

Big bats binge bad bugs: Variation in crop pest consumption by common bat species

As generalist predators, insectivorous bats exploit fluctuations in prey distribution and abundance. A more nuanced understanding of the influence of bats on arthropod pests requires documentation of the pest species bats consume and of the conditions associated with variation in rates of pest consumption. Here, we used high-throughput metabarcoding of DNA extracted from bat feces to investigate diets of 180 bats representing three Vespertilionidae species common to the southeastern US, a region dominated by agriculture and pine plantations. We detected 23 species of agricultural pests in bat diets, including pests responsible for severe economic damage, such as Helicoverpa zea, Spodoptera frugiperda, Chloridea virescens and Chrysodeixis includens. Incidence of pest consumption was high: 61% of all bats had consumed at least one agricultural pest species, with each bat consuming an average of 1.7 pest species. The likelihood of consumption of pests to row crops and the average size of pests consumed varied by bat species, with a large foliage-roosting species (Lasiurus seminolus) consuming a greater variety of pest species and pest species larger in size than smaller crevice, cavity, and cave roosting bat species (Nycticeus humeralis, Myotis austroriparius). Likelihood of pest consumption also varied among sampling periods (season) and among bats of different sizes (as reflected by wing length and mass). Overall, likelihood of pest consumption was higher in the late summer season than during spring or early summer, and higher among larger bats than smaller bats. Bat characteristics and seasonality were generally more effective than geographic features and weather conditions in predicting pest consumption patterns. Strategies for enhancing pest consumption services by bats in agroecosystems should strive to maintain and enhance diverse bat populations on a landscape scale by protecting and augmenting roost structures appropriate for each species. Our finding of widespread pest consumption by bats contributes to mounting evidence worldwide of the important role bats play in agricultural systems and highlights the value of incorporating bat conservation into integrated pest management programs globally.

Barn Owls select uncultivated habitats for hunting in a winegrape growing region of California

Abstract Large-scale conversion of uncultivated land to agriculture threatens wildlife and can diminish ecosystem services provided by nature. Understanding how wildlife provision ecosystem services may incentivize wildlife conservation in agricultural landscapes. Attracting Barn Owls (Tyto furcata) to nest on farms for pest management has been implemented worldwide but has not been evaluated in vineyard agroecosystems. Napa Valley, California, is a renowned winegrape growing region, and viticulturists encourage Barn Owl occupancy to help minimize damage from Botta’s pocket gophers (Thomomys bottae) and voles (Microtus spp.). This study modeled the use of habitats in space and time by hunting Barn Owls, providing information about their potential to provide the critical ecosystem service of pest consumption. We used global positioning system tags to track hunting owls and used a resource selection function to compare used and available habitats. We constructed the intensity of use and home range-movement maps using a time local convex hull analysis from location data. We found that Barn Owls selected uncultivated habitats when hunting, some of which were relatively rare on the landscape. Approximately, one-third of Barn Owl hunting locations occurred in vineyards, but this use was out of proportion to the availability of vineyards, which comprised 50% of the area around nest boxes. The owls’ use of vineyards increased with decreasing amount of selected uncultivated habitat in the landscape. However, as reported by a previous study, the occupancy of nest boxes in vineyards increases with uncultivated habitats nearby. Future research should model landscape composition to determine the amount of preferred habitat necessary to support occupancy as well as hunting in vineyards. A true test of pest management by Barn Owls awaits experimentation coupled with monitoring rodent populations.

A famous failure: Why were cane toads an ineffective biocontrol in Australia?

AbstractIn 1935, cane toads (Rhinella marina) were brought to Australia to control insect pests. The devastating ecological impacts of that introduction have attracted extensive research, but the toads' impact on their original targets has never been evaluated. Our analyses confirm that sugar production did not increase significantly after the anurans were released, possibly because toads reduced rates of predation on beetle pests by consuming some of the native predators of those beetles (ants), fatally poisoning others (varanid lizards), and increasing abundances of crop‐eating rodents (that can consume toads without ill‐effect). In short, any direct benefit of toads on agricultural production (via consumption of insect pests) likely was outweighed by negative effects that were mediated via the toads' impacts on other taxa. Like the toad's impacts on native wildlife, indirect ecological effects of the invader may have outweighed direct effects of toads on crop production.

Quantifying ecological and economic value of pest control services provided by bats in a vineyard landscape of central Chile

The top-down suppression of pest insects by their natural enemies, such as insectivorous bats, represents an important ecosystem service in agricultural systems. Recognizing the importance of bats to suppress pest populations and further conserve their populations near agricultural systems could reduce damage to crops thereby potentially increasing the monetary gain of farmers. Viticulture represents one of the most extensive and economically important agricultural crops in the Mediterranean biome. While pest consumption by bats has been recently revealed in vineyards, direct evidence of the reduction of grapevine pests by bats in vineyards is lacking, and their benefits to winegrape production remains to be quantified. Using large nocturnal exclosures in vineyards, we examined the top-down effects of aerial insectivorous bats in suppressing insect populations by assessing leaf and grape cluster damage; we also examined the benefit of these natural pest predators by quantifying resulting increases in potential vineyard yield. Grapevine plants excluded from bats had significantly higher leaf herbivory and greater grape cluster damage than control plots. Grape cluster damage was 7% lower on control plots, yielding an average economic benefit of US$188-$248/ha/year due to bat predation. These results provide the first experimental evidence that bats reduce grapevine pest insect infections and thus increase vineyard yield and winegrowers’ income. Therefore, bats should be included in future biodiversity conservation plans in vineyards and be considered within agricultural management strategies based on natural pest suppression.

Instar Determination of Blaptostethus pallescens (Hemiptera: Anthocoridae) Using Artificial Neural Networks

Abstract Blaptostethus pallescens Poppius is an important predator of vegetable pests in tropical regions. The correct identification of the stages of the life cycle of predatory species is crucial, since different stages may present different rates of pest consumption. Artificial neural networks (ANNs) are computational tools with a structure based on the human brain. With applications in several fields, ANNs have been applied in pest management for identification of pest species, spatial distribution modeling, and insect forecasting. The objective of this study was to apply ANNs as a method for the instar determination of B. pallescens using three morphometric measures (head width, body width, and body length). Cluster analysis was performed to categorize the insects in instars according to the morphometric variables. Subsequently, the ANNs were trained for instar determination using the morphometric measures as input variables. The ANNs tested (with 2, 4, 6, 8, 10, and 12 hidden neurons) provided proper data fitting (R2 > 98%). However, due to the parsimony principle, the network with hidden layer size 6 was selected. This study shows the successful application of ANNs in the instar determination of B. pallescens, which would not be possible using classical methods.

Sympatric Bat Species Prey Opportunistically on a Major Moth Pest of Pecans

Native predators provide undervalued pest suppression services to agriculture. Studies of pest consumption by insectivorous bats tend to focus upon single species in large, centralized colonies, while bats dispersed in small groups within the agricultural matrix often go unnoticed. Pecan trees, Carya illinoinensis, and the destructive pecan nut casebearer (PNC) moth, Acrobasis nuxvorella, comprise a tightly linked host–parasite system in a widespread agroecosystem native to North America. Here we use a quantitative polymerase chain reaction (qPCR) assay of fecal DNA to document predation on PNC moths by an assemblage of sympatric bat species across episodic peaks in PNC abundance. Although five species of bats consume PNC moths, greater predation by a solitary tree-roosting bat (eastern red bat, Lasiurus borealis) than other species is suggested by a higher frequency of PNC occurrence and quantity of PNC gene copies in fecal samples. Consumption of PNC by bats during all documented peaks in moth activity suggests that predation pressure occurs throughout the PNC season. Our results highlight the need to consider multi-species assemblages and different foraging strategies when assessing pest suppression services, particularly in agroforestry or tree crops. Assessing the diet of only common or easily captured species limits our ability to accurately document pest consumption by bats.

Pest consumption in a vineyard system by the lesser horseshoe bat (Rhinolophus hipposideros).

Herbivorous arthropods cause immense damage in crop production annually. Consumption of these pests by insectivorous animals is of significant importance to counteract their adverse effects. Insectivorous bats are considered amongst the most voracious predators of arthropods, some of which are known crop pests. In vineyard-dominated Mediterranean agroecosystems, several crops are damaged by the attack of insect pests. In this study we aimed 1) to explore the diet and pest consumption of the lesser horseshoe bat Rhinolophus hipposideros and 2) analyse whether the composition of pest species in its diet changes throughout the season. We employed a dual-primer DNA metabarcoding analysis of DNA extracted from faeces collected in three bat colonies of a wine region in Southwestern Europe during the whole active period of most pest species. Overall, 395 arthropod prey species belonging to 11 orders were detected; lepidopterans and dipterans were the most diverse orders in terms of species. Altogether, 55 pest species were identified, 25 of which are known to cause significant agricultural damage and 8 are regarded as pests affecting grapevines. The composition of pest species in faeces changed significantly with the season, thus suggesting several periods should be sampled to assess the pest consumption by bats. As a whole, the results imply that R. hipposideros acts as a suppressor of a wide array of agricultural pests in Mediterranean agroecosystems. Therefore, management measures favouring the growth of R. hipposideros populations should be considered.

The 'Botanical Triad': The Presence of Insectary Plants Enhances Natural Enemy Abundance on Trap Crop Plants in an Organic Cabbage Agro-Ecosystem.

Habitat manipulation through the incorporation of non-crop plants such as trap crops (to lure pests away from the cash crop) and insectary plants (to provide resources for natural enemies) into agro-ecosystems is an ecological approach to pest management. In a field-scale study, we quantified the effects of integrating the use of trap crops with insectary plants as a novel method to control pest herbivores in an organic cabbage agro-ecosystem. We hypothesized that pests would be concentrated in the trap crop habitat and suppressed by insectary-subsidized natural enemies in situ. We documented arthropod abundance (both adults and immature stages) associated with (1) two insectary plant species (sweet alyssum, Lobularia maritima, and buckwheat, Fagopyrum esculentum) either alone or in combination; (2) a trap crop mixture of mighty mustard (Brassica juncea), red Russian kale (Brassica oleracea var. acephala), and glossy collards (Brassica oleracea var. italica), and (3) cabbage cash crop (Brassica oleracea var. capitata). Trap crops were more attractive to pests than the cash crop. On a per-plant basis, densities of the herbivores Evergestis rimosalis, Trichoplusia ni, and Plutella xylostella were 154, 37, and 161× greater on the kale trap crop than on the cabbage cash crop, and 54, 18, and 89× greater on the collards trap crop than on the cash crop. Insectary plants contributed to the consumption of pests that aggregated on the trap crop. Parasitism of E. rimosalis by the braconid wasp Cotesia orobenae was significantly increased, and the abundance of eggs and larvae of the predatory coccinellid beetle Coleomegilla maculata was greater on the trap crop in the presence of insectary plants compared to trap crops that lacked insectary plants. The ‘Botanical Triad’ of cash crop, trap crop, and insectary plants represents a new type of agro-ecosystem manipulation that integrates ecosystem service providers (e.g., predators and parasitoids) within the cropping system.

Insect pest consumption by bats in macadamia orchards established by molecular diet analyses

The diet of insectivorous bat species is difficult to study and the least invasive tool to gain information on these predators’ foraging preferences is the study of their faecal pellets. The aim of this study was to determine whether bats consumed insect pest species in macadamia orchards, with the additional goal of incentivising farmers to adopt a more integrated pest management approach (IPM). We used a molecular approach to provide insight into insectivorous bat diet, analysing pellets with fluorescent-labelled and species-specific primers (COI). Faecal pellets were collected from captured individuals or from trays installed underneath bathouses and roosts between July 2015 and April 2017 in the Levubu region, Limpopo, South Africa. Four of the main insect pests, two moth (Lepidoptera: Tortricidae) and two stinkbug (Hemiptera: Pentatomidae) species, were collected for species-specific primer development and assay optimisation. We extracted DNA from the faecal pellets and amplified the target regions of the four target pest species present. To verify the results of the fragment analyses we also sequenced all PCR products.All the species or families of bats from which pellets were collected foraged on at least one of the four major insect pests, with insect pest sequences obtained and confirmed from 57 out of 103 samples (55%). Bats consumed insect pests throughout the macadamia growing seasons and are much more generalist and presumably opportunistic feeders than previously assumed. Nearly all species and families of bats analysed foraged on both the Lepidopteran and Hemipteran insect pest species. In conclusion, bats appear to be important for pest control and we suggest that farmers should maintain or restore (semi-)natural vegetation inside and adjacent to their farms. Adding water sources and roosting opportunities, and minimizing pesticide treatments may furthermore promote bat activity.

Limb Regeneration and Interference Competition Consequences on Foraging Efficiency of Coccinella undecimpunctata and Hippodamia variegata (Coccinellidae: Coleoptera) to Their Prey, Aphis craccivora (Hemiptera: Aphididae).

Regeneration of limbs lost during development has been recorded in a large number of species of hexapoda including many Coccinellids. Although regeneration has obvious survival and fitness benefits, it has also been demonstrated to impose costs on development, reproduction, and behavior. To investigate consequences of regeneration on foraging behavior, Coccinella undecimpunctata L. and Hippodamia variegata (Goeze) larvae were treated to remove one limb, allowed to pupate and regenerate and then prey searching ability assessed. Different densities of adults were placed in Petri dishes with aphid prey and consumption assessed over a 24-h period. Amputation/regeneration, predator species, and predator density significantly affected the total number of aphids consumed. Aphid consumption rates and predation efficiency of both regenerated and control beetles significantly increased as predator density increased. Although there were significant differences in consumption between ablated/regenerated and control C. undecimpunctata at each predator densities, H. variegata did not. Further, mutual interference was significantly higher for regenerated compared with control C. undecimpunctata but not so for H. variegata. This is the first demonstration of an effect of ablation/regeneration on foraging behavior of C. undecimpunctata and suggests that H. variegata demonstrates an adaptive phenotypic response to limb regeneration. Coccinellids are widely used as biological agents and these findings concerning the impact of variation in predator density have clear implications for the management of predator-prey ratios in order to maximize efficiency of pest consumption.

Predation-mediated ecosystem services and disservices in agricultural landscapes.

Ecological intensification may reduce environmental externalities of agriculture by harnessing biodiversity to benefit regulating ecosystem services. However, to propose management options for the production of such services, there is a need to understand the spatiotemporal dynamics of net effects between ecosystem services and disservices provided by wild organisms across taxonomic groups in relation to habitat and landscape management. We studied the contribution of predatory vertebrates and invertebrates (including both carnivores and seed herbivores) to regulating ecosystem services and disservices in 16 cereal fields in response to a local habitat contrast and a landscape complexity gradient. From May to November 2016, we provided weed (predation reflects an ecosystem service) and crop (predation reflects a disservice) seeds, as well as pest (predation reflects an ecosystem service) and beneficial (predation reflects a disservice) invertebrate prey to predators. Seed predation was dominated by vertebrates, while vertebrates and invertebrates contributed equally to predation of animal prey. Before harvest, predation steadily increased from very low levels in May to high levels in July independent of the resource type. After harvest, ecosystem services declined more rapidly than disservices. The presence of adjacent seminatural grasslands promoted crop seed predation, but reduced pest prey predation. Predation on beneficial prey decreased with increasing proportions of seminatural grassland in the landscape. Predatory vertebrates and invertebrates provide important ecosystem services due to the consumption of pests. However, beneficial invertebrates and crop seeds were often consumed to a similar or even higher extent than harmful invertebrates or weed seeds. Our results therefore raise concerns that management options aimed at enhancing service providers may simultaneously increase levels of disservices. By considering positive and negative effects simultaneously, this study addresses an important knowledge gap and highlights the importance of interactions between local management, landscape composition, and service and disservice provision across taxa and over time. Considering trade-offs between ecosystem services and disservices when evaluating the net effects of biodiversity conservation measures on ecosystem service provision is crucial. Future agri-environment schemes that offer payments for seminatural habitats may need to provide higher compensation for farmers in cases where net effects are likely to be negative.

Diet Determined by Next Generation Sequencing Reveals Pest Consumption and Opportunistic Foraging by Bats in Macadamia Orchards in South Africa

Recent studies have documented the economically significant impact of bats as predators of agricultural pest insects. We used Next Generation Sequencing (NGS) of the cytochrome oxidase I gene to elucidate the diet of six species of bats based on faecal pellets collected from individuals and roosts in macadamia orchards at Levubu, Limpopo Province, South Africa. For five of these species, we compared the molecular data with published results from microscopic analysis of faecal pellets, culled parts and stomach contents. We provide the first description of the molecular diet of the large African molossid bat, Mops midas. Expectations from skull morphology and a single limited study of stomach contents were that this species should be a beetle-specialist. However, NGS revealed that the diet of M. midas contained a much higher prevalence and diversity of lepidopteran (81 taxa from 17 families) compared to coleopteran (two taxa) prey. While this result is predicted by the allotonic frequency hypothesis for a bat species with low echolocation frequency, it could also be explained by unequal PCR amplification, a constraint of amplicon sequencing. Apart from the above-mentioned species where our sample was probably unbiased (24 pellets from multiple roosts and occasions), sample sizes of the other five species were very low and therefore potentially biased (1–6 pellets). Nevertheless, these samples revealed for each bat species surprisingly many prey taxa spanning several insect orders, indicating that individual bats were capable of consuming a wide diversity of prey during one or two nights of foraging. Contrary to expectations, bats of all foraging groups (clutter, clutteredge and open-air) fed opportunistically on mostly-flightless cockroaches (Order Blattodea). About one third of all faecal pellets tested from five species of bats of all foraging groups contained DNA from the significant macadamia pest species, Nezara viridula (Order Heteroptera), indicating the value of intact bat communities in the biological control of pest stink bugs in macadamia orchards. Contrary to the general expectations of the allotonic frequency hypothesis, all six bat species studied fed predominantly on tympanate versus non-tympanate species of moths (57–75% of lepidopteran prey taxa), even those ‘non-allotonic’ bat species having intermediate echolocation peak frequencies that encompass the frequency sensitivity of hearing (tympanate) moths.

Estimating the effect of plant-provided food supplements on pest consumption by omnivorous predators: lessons from two coccinellid beetles.

Plant-provided food supplements can influence biological pest control by omnivorous predators in two counteracting ways: they can (i) enhance predator populations, but (ii) reduce pest consumption by individual predators. Yet the majority of studies address only one of these aspects. Here, we first tested the influence of canola (Brassica napus L.) pollen supplements on the life history of two ladybeetle species: Hoppodamia variegata (Goeze) and Coccinella septempunctata (L.). We then developed a theoretical model to simulate total pest consumption in the presence and absence of pollen supplements. Supplementing a prey diet with canola pollen increased H. variegata larval survival from 50 to 82%, and C. septempunctata female oviposition by 1.6-fold. Model simulations revealed a greater benefit of pollen supplements when relying on C. septempunctata for pest suppression than on H. variegata. For these two predators, the tested pollen serves as an essential supplement to a diet of prey. However, the benefit of a mixed prey-pollen diet was not always sufficient to overcome individual decrease in pest consumption. Taken together, our study highlights the importance of addressing both positive and negative roles of plant-provided food supplements in considering the outcome for biological control efforts that rely on omnivorous predators. © 2016 Society of Chemical Industry.

Frogs as potential biological control agents in the rice fields of Chitwan, Nepal

Anuran frogs are often considered generalist predators in rice fields and feed upon a variety of invertebrates. They may thus provide an invaluable ecosystem service, as many species belonging to the orders coleoptera, lepidoptera, orthoptera, homoptera and hemiptera are regarded as notorious rice pests, inflicting significant losses on rice production. In this study, we surveyed frogs in rice paddies of lowland Nepal during the dry and rainy seasons, approximately 3–4 weeks after rice had been planted. We used stomach flushing to study the dietary habits of anuran species encountered, and provide empirical evidence of the ecological service provided by frogs in this agricultural landscape. We found that frogs included a high proportion of crop pests in their diet, but consumption of pests varied between the rainy and dry seasons, frog species and even individual frogs. The ecosystem services provided by frogs are not limited to crop pest control, but, as our observations revealed, include consumption of a large number insects known to be important vectors of zoonotic diseases. We encourage both farmers and conservation planners to consider frogs as important biological pest controllers during the development of pest management and strategies in agricultural landscapes.

Prey and Pollen Food Choice Depends on Previous Diet in an Omnivorous Predatory Mite.

The time allocated by omnivorous predators to consuming prey versus plant-provided foods (e.g., pollen) directly influences their efficacy as biocontrol agents of agricultural pests. Nonetheless, diet shifting between these two very different food sources remains poorly understood. We hypothesized that previous diet composition influences subsequent choice of prey and plant food types. We tested this hypothesis by observing the foraging choices of Amblyseius swirskii (Athias-Henriot) mites (Mesostigmata: Phytoseiidae), which were first maintained on either prey (broad mites) or corn pollen, and then offered familiar and unfamiliar foods. A. swirskii exhibited strong fidelity to familiar food, whether prey or pollen, suggesting there are physiological or behavioral costs involved in shifting between such different foods. Results illustrate the importance of previous diet for subsequent pest consumption by omnivorous natural enemies.

Confronting and resolving competing values behind conservation objectives

Diverse motivations for preserving nature both inspire and hinder its conservation. Optimal conservation strategies may differ radically depending on the objective. For example, creating nature reserves may prevent extinctions through protecting severely threatened species, whereas incentivizing farmland hedgerows may benefit people through bolstering pest-eating or pollinating species. Win-win interventions that satisfy multiple objectives are alluring, but can also be elusive. To achieve better outcomes, we developed and implemented a practical typology of nature conservation framed around seven common conservation objectives. Using an intensively studied bird assemblage in southern Costa Rica as a case study, we applied the typology in the context of biodiversity's most pervasive threat: habitat conversion. We found that rural habitats in a varied tropical landscape, comprising small farms, villages, forest fragments, and forest reserves, provided biodiversity-driven processes that benefit people, such as pollination, seed dispersal, and pest consumption. However, species valued for their rarity, endemism, and evolutionary distinctness declined in farmland. Conserving tropical forest on farmland increased species that international tourists value, but not species discussed in Costa Rican newspapers. Despite these observed trade-offs, our analyses also revealed promising synergies. For example, we found that maintaining forest cover surrounding farms in our study region would likely enhance most conservation objectives at minimal expense to others. Overall, our typology provides a framework for resolving the competing objectives of modern conservation.

Molecular diagnosis of bird-mediated pest consumption in tropical farmland.

Biodiversity loss will likely have surprising and dramatic consequences for human wellbeing. Identifying species that benefit society represents a critical first step towards predicting the consequences of biodiversity loss. Though natural predators prevent billions of dollars in agricultural pest damage annually, characterizing which predators consume pests has proven challenging. Emerging molecular techniques may illuminate these interactions. In the countryside of Costa Rica, we identified avian predators of coffee’s most damaging insect pest, the coffee berry borer beetle (Coleoptera:Scolytidae Hypothenemus hampeii), by assaying 1430 fecal samples of 108 bird species for borer DNA. While feeding trials confirmed the efficacy of our approach, detection rates were low. Nevertheless, we identified six species that consume the borer. These species had narrow diet breadths, thin bills, and short wings; traits shared with borer predators in other systems. Borer predators were not threatened; therefore, safeguarding pest control necessitates managing species beyond those at risk of regional extinction by maintaining populations in farmland habitats. Generally, our results demonstrate potential for pairing molecular methods with ecological analyses to yield novel insights into species interactions.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-630) contains supplementary material, which is available to authorized users.

What happens when crops are turned on? Simulating constitutive volatiles for tritrophic pest suppression across an agricultural landscape

Herbivore-induced plant volatiles, or HIPVs, are increasingly considered as a biocontrol enhancement tool by constitutively emitting these carnivore-attracting chemicals from agricultural fields. While ample data substantiate the olfactory preference of predators for HIPVs in laboratory environments, little is understood about the consequences of 'turning crops on' in the field. To explore the ramifications for arthropod pest management, a spatially explicit predator-prey population model was constructed that simulated a crop field releasing signals to recruit natural enemies from the surrounding landscape. Field size had an overriding influence on model outcome, both isolated as a single factor and interactively shaping responses to other parameters (e.g. habituation, foraging efficiency). Predator recruitment exponentially declined with increasing field size from nearly double the baseline density in small fields (225 individuals m(-2)) to a mere 4% increase (130 individuals m(-2)) in large fields. Correspondingly, HIPVs enhanced pest consumption in small fields (ca 50% fewer prey), while generating virtually no impact in large fields. Collectively, the model suggests that reducing the perimeter/core area ratio will ultimately constrain the utility of predator retention as a pest control tactic in commercial-sized fields and illustrates potential consequences of the widespread commercialization of this technology in agriculture.

Effects of land use on bird populations and pest control services on coffee farms

Global increases in both agriculture and biodiversity awareness raise a key question: Should cropland and biodiversity habitat be separated, or integrated in mixed land uses? Ecosystem services by wildlife make this question more complex. For example, birds benefit agriculture by preying on pest insects, but other habitat is needed to maintain the birds. Resulting land use questions include what areas and arrangements of habitat support sufficient birds to control pests, whether this pest control offsets the reduced cropland, and the comparative benefits of "land sharing" (i.e., mixed cropland and habitat) vs. "land sparing" (i.e., separate areas of intensive agriculture and habitat). Such questions are difficult to answer using field studies alone, so we use a simulation model of Jamaican coffee farms, where songbirds suppress the coffee berry borer (CBB). Simulated birds select habitat and prey in five habitat types: intact forest, trees (including forest fragments), shade coffee, sun coffee, and unsuitable habitat. The trees habitat type appears to be especially important, providing efficient foraging and roosting sites near coffee plots. Small areas of trees (but not forest alone) could support a sufficient number of birds to suppress CBB in sun coffee; the degree to which trees are dispersed within coffee had little effect. In simulations without trees, shade coffee supported sufficient birds to offset its lower yield. High areas of both trees and shade coffee reduced pest control because CBB was less often profitable prey. Because of the pest control service provided by birds, land sharing was predicted to be more beneficial than land sparing in this system.

Semiochemical lures reduce emigration and enhance pest control services in open-field predator augmentation

Augmentation biocontrol is a commercially viable pest management tactic in enclosed glasshouse environments, but is far less effective in open-field agriculture where newly released enemies rapidly disperse from release sites. We tested the potential for behavior-modifying semiochemicals to increase the retention of mass released predatory stink bugs, Podisus maculiventris Say (Hemiptera: Pentatomidae), for enhanced consumption of hornworm caterpillars, Manduca sexta L. (Lepidoptera: Sphingidae). To do so, we used controlled-release dispensers to emit the herbivore-induced plant volatile, methyl salicylate (MeSA), or P. maculiventris aggregation pheromone from tomato field plots. Overall, we recaptured ca. 17% of released individuals after 36h. This rate, however, was significantly affected by weather (12% vs. 22% recapture in rainy vs. dry weeks, respectively) and semiochemical deployment, but only under optimal weather conditions (19% vs. 26% recapture in control vs. pheromone plots, respectively, during dry weeks). Further, we detected behavioral responses of wild P. maculiventris to semiochemical treatment with 94% of all captured adults (=84 of 89 total) found in pheromone plots. Only 24 of 567 (4%) captured stink bugs tested positive for immunomarking, suggesting that hornworm predation occurred but at a low frequency. Importantly, we documented that sentinel caterpillar prey were depleted by predators at a higher rate in stink bug augmented plots on tomato plants occurring near (<3m from) the MeSA and pheromone lures. These data empirically demonstrate that both semiochemicals are capable of increasing pest consumption via attraction of P. maculiventris. Future work should focus on mechanisms of lure attraction and the long-term consequences of predator development in fields with elevated semiochemical emissions.