Conservation Biological Control Programs Research Articles

Assessing the efficacy of un and gamma-irradiated entomopathogenic nematode, Steinernema carpocapsae as an eco-friendly approach to control Agrotis ipsilon larvae

The black cutworm, Agrotis ipsilon (Hufnagel) is one of the most devastating agricultural pests that attack different crops worldwide. Entomopathogenic nematodes (EPNs) have been utilized in classical, conservation, and augmentative biological control programs. Consequently, this study was designed to estimate the efficacy of an unirradiated and gamma-irradiated entomopathogenic nematode, Steinernema carpocapsae (all), against A. ipsilon larvae as a safe control tool to reduce chemical environmental hazards. The virulence of different concentrations (10, 20, 30 and 40 IJs/ml) of unirradiated and gamma-irradiated (with 2 Gy) of S. carpocapsae was evaluated. Changes in peroxidase (Px) and polyphenyl oxidase (PPO) zymographic patterns were also investigated after larvae were treated with LC50 values for S. carpocapsae. The results revealed that larval mortality increased with increasing S. carpocapsae concentration and time after treatment. The 2 Gy gamma-irradiated S. carocapsae caused a greater pathogenic effect than the unirradiated S. carocapsae, where the LC50 values of 2 Gy gamma-irradiated S. carocapsae were 31.19 and 17.78 IJs/ml after 1 and 2 days, respectively, compared to 113.23 and 65.83 IJs/ml for unirradiated S. carocapsae. For the toxicity index, gamma irradiation at a dose of 2 Gy was selected and given an arbitrary 100 units and considered a standard treatment. Analysis of gel electrophoresis revealed 3 bands of Px and PPO in control larvae; treatment with unirradiated and irradiated S. carpocapsae caused the disappearance of the first band of both enzymes and lowered the intensity of the other 2 bands. The laboratory studies revealed that 2 Gy gamma-irradiated S. carpocapsae could be used as an eco-safe management tool against A. ipsilon larvae under field conditions.

Ecosystem services of soil predatory mites depend on a functional soil food web

Species of soil predatory mites feed on a diverse diet making them excellent candidates for conservation biological control programs. Free living nematodes (FLNs) are commonly found in soils at all trophic levels and serve as prey for many soil predatory mites (SPMs) in a functional soil food web. Here we present highlights of two case studies and the preliminary results of one ongoing study, all with the common aim of improving the conservation of soil predatory mites for the control of soil pests. In the first study, we used Macrocheles embersoni for housefly control (Azevedo et al., 2019), in the second, Stratiolaelaps scimitus for the control of the root knot nematode (RKN) Meloidogyne incognita (Azevedo et al., 2020), and in the third, we use frass of black soldier fly Hermetia illucens as an organic amendment for harnessing the local soil food web for the control of RKN. In the first two studies, complementing the diet of predatory mites with the FLN Rhabditella axei in their culture medium resulted in higher predator abundance and better biological control, compared to the negative control and the release of predators without FLNs and microbiota. In the third study the effect of the soil amendment on soil biota and RKN control differed among soils. We expect that soil amendments alter biocontrol efficacy, and that these effects are dependent on the biodiversity of soil biota as well as abiotic soil properties, and that caring for soils is a pre-requisite for successful conservation biological control.

Irrigation modulates entomopathogenic nematode community and its soil food web in olive groves under different agricultural managements

Entomopathogenic nematodes (EPNs) are biological control agents distributed worldwide in natural and agricultural soils. Recent evidence supports the hypothesis that stable rhizospheres of perennial crops can favor the occurrence of EPNs. However, different agricultural management practices can modulate their natural distribution in agroecosystems, hence should be considered in conservation biological control programs to support as high as possible native EPN populations. Cultivated olive (Olea europaea subsp. europaea), originally from the Mediterranean Basin, is a key perennial crop susceptible to a diverse range of arthropod pests that account for their life with at least one soil inhabitant stage. In this study, we investigated, for the first time, the occurrence of EPNs and associated soil organisms in olive groves managed with different practices. We surveyed 89 commercial olive groves located in Andalusia (Southern Spain) and differently handled for pest management (conventional vs. organic), soil management (tilling vs. cover cropping), and irrigation regime (rain feed vs. drip-irrigation). By using species-specific primers-probe sets and quantitative real-time PCR approaches, we screened the occurrence of nine species of EPNs, five free-living nematodes (FLNs), and six nematophagous fungi (NF). We found EPNs in 23.6% of the sites, identifying only two EPN species: Steinernema feltiae (15.7%) and Heterorhabditis bacteriophora (7.9%). Pest and soil management did not affect EPN abundance, but drip irrigation increased their occurrence (P < 0.025). On the contrary, we recorded lower FLN numbers in irrigated groves (P = 0.003), particularly for Oscheius tipulae and Pristionchus maupasi. Regarding NF, both organic management (P < 0.001) and drip irrigation (P < 0.035) enhanced their abundance. Four abiotic explanatory variables (extractable P, clay content, elevation, and precipitation) explained 85.6% of the EPN, FLN, and NF species variation in multivariate analysis. Overall, drip irrigation in the olive groves enhanced the EPN community but also NF growth, natural enemies of nematodes. Additional studies are required to determine the best combination of alternative strategies that will enhance a balanced soil biota in olive groves in Mediterranean regions and other areas where this crops is cultivated that enable conservation ecosystem services, such as those provided by the EPNs.

Development, Predation, and Prey Preference of Chrysoperla externa on Liorhyssus hyalinus and Nysius simulans, Two Emerging Pests of Quinoa.

In recent years, Liorhyssus hyalinus (Fabricius) (Hemiptera: Rhopalidae) and Nysius simulans Stål (Hemiptera: Lygaeidae) have emerged as important pests of quinoa in Peru, when the crop started to be cultivated at relatively low elevations. The potential of the native lacewing Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) was evaluated as a biological control agent of these two pest species. Prey consumption on all immature stages of L. hyalinus and N. simulans was assessed, as well as development on first instars of these heteropterans and eggs of Sitotroga cerealella (Olivier) (Lepidoptera: Pyralidae) as a factitious prey. In addition, prey preference was examined in the absence and presence of a preferred prey, Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae). Larvae of the predator were not able to feed on L. hyalinus eggs, but they effectively did on N. simulans eggs as well as on all nymphal instars of both species. Nymphs of L. hyalinus were less suitable prey for larval development of C. externa than eggs of S. cerealella, whereas N. simulans was overall an unsuitable prey. There was a clear prey preference of C. externa for aphids over the two heteropteran species, as well as a preference for N. simulans over L. hyalinus. The predation rates in this study indicate the potential of C. externa as a predator of these heteropteran pests that can play a role in both conservation and augmentation biological control programs.

Molecular tracking of insect dispersal to verify arthropod predator movement from an alfalfa field to a peach orchard

Implementation of landscape approaches to conservation biological control programs requires the confirmation of putative sources that contribute to predator colonization of crops. This study aims to confirm predator dispersal from an alfalfa field to a neighboring peach orchard with a DNA mark-capture procedure based on a topical application of a solution of grinded brine shrimp cysts, Artemia spp. (Anostraca: Artemiidae), followed by a conventional PCR.To optimize the marking procedure, a well-known predator present in orchards as well as in arable crops, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae), was used as a model in this study. In greenhouse trials, the acquisition and the retention time of the Artemia markings were determined, either directly by spraying them with the Artemia solution or indirectly via residual contact on caged plants after the spray. The topical mark remained detectable on O. laevigatus after 6 days, and 50% of the tested predators were positive 3 days after walking on the sprayed plants.After that, a 25m2 strip of an alfalfa crop neighboring to a peach orchard was sprayed with the Artemia solution just after the alfalfa cuts, and several common predator species were collected using sticky traps placed between both crops. After PCR analysis with the Artemia specific primers, 32% of the analyzed predators (coccinellids, anthocorids, chrysopids, and mirids) showed the mark. The results of this study confirm the usefulness of this marking method to monitor dispersal of biological control agents between neighboring crops, in this case alfalfa and peach.

Development of a PCR-based method to monitor arthropod dispersal in agroecosystems: Macrolophus pygmaeus (Hemiptera: Miridae) from banker plants to tomato crops.

Development of conservation biological control programs requires the identification of sources that contribute to predator colonization of crops. Macrolophus pygmaeus (Rambur) (Hemiptera: Miridae) is an efficient polyphagous predator used in biological control programs in vegetable crops in Europe. We have developed a marking method based on spraying with a solution of the brine shrimp Artemia spp. (Anostraca: Artemiidae) cysts, followed by a PCR detection of Artemia DNA to monitor M. pygmaeus dispersal from banker plants to tomato crops. Experiments conducted in climatic chambers show that the topical application of this marking solution on M. pygmaeus does not significantly reduce adult longevity and that it is detected up to 6 d after the application. When this Artemia solution was applied on Calendula officinalis L. banker plants harboring M. pygmaeus and maintained outdoors, Artemia DNA was still detected on 62% of the insects after 6 d. The conducted field applications in commercial greenhouses have confirmed the usefulness of this method to monitor M. pygmaeus dispersal from banker plants to a newly planted tomato crop. This method can be used to assess arthropod movement, being an interesting molecular approach for further improving future pest management strategies.

Do Floral Resources Benefit the Herbivorous Sawfly, Cephus cinctus (Hymenoptera: Cephidae), a Major Pest of Wheat in North America?

Leveraging floral resources to promote biological control requires carefully screening prospective floral species for their suitability not just for natural enemies, but also for targeted pests. Here we examined the influence of access to various sugar resources on Cephus cinctus Norton (Hymenoptera: Cephidae), a major pest of wheat in the northern Great Plains of North America. We conducted greenhouse studies to examine the effect of access to a honey-sucrose solution, three flowering plant species, and aphid honeydew, on the longevity and potential fecundity of C. cinctus. Cephus cinctus longevity increased significantly (females living 1.18-1.25 times as long) in treatments with buckwheat (Fagopyrum esculentum Moench (Polygonales: Polygonaceae)) flowers compared with controls. In contrast, there was no significant effect of two additional mustard species (Capparales: Brassicaceae) tested, canola (Brassica napus L.) and white mustard (Sinapis alba L.), or aphid (Myzus persicae Sulzer (Hemiptera: Aphididae)) honeydew on C. cinctus longevity. Access to buckwheat did not significantly increase the cumulative number of eggs laid by C. cinctus, suggesting that sugar feeding on this plant is unlikely to increase pest impacts. To our knowledge, this is the first published experimental evidence that access to floral resources can increase the adult lifespan of C. cinctus. The results re-inforce previous observations that sugar feeding may be common in Cephus spp. and other Cephidae. Our results further suggest that screening prospective floral species being considered for conservation biological control programs against both C. cinctus and potential parasitoids will be an important precautionary measure in future work.

Innate and learned olfactory attraction to flowering plants by the parasitoid Cotesia rubecula (Marshall, 1885) (Hymenoptera: Braconidae): Potential impacts on conservation biological control

In conservation biological control, flowers can be used to increase the biological control potential of parasitoids, which benefit from the offered food sources. Besides exhibiting exploitable nectar, flowers should preferably be olfactorily attractive, as highly attractive flowers are easily located, reducing the time spent searching for food and subsequently increasing the per capita host searching efficiency. In this study we thus focused on the olfactory attractiveness of Fagopyrum esculentum Moench (Polygonaceae), Centaurea cyanus L. (Asteraceae) and Vicia sativa L. (Fabaceae) to Cotesia rubecula (Marshall, 1885) (Hymenoptera: Braconidae), a larval parasitoid of the cabbage pest Pieris rapae (Linnaeus, 1758) (Lepidoptera: Pieridae). With a Y-tube olfactometer we found that C. cyanus and to a lesser extent V. sativa successfully attract C. rubecula. Also F. esculentum attracts C. rubecula, but only after a rewarding feeding experience. All three tested flowers seem to be suitable to be exploited in conservation biological control programs to control P. rapae in brassica fields. Even though not every flower offering accessible nectar is also innately attractive, it can still be suitable for conservation biological control purposes as feeding experience can change this attraction. In fact, the application of mixtures containing attractive and rewarding flowers could help increase the success of such programs.

Contrasting olfactory responses of two egg parasitoids to buckwheat floral scent are reflected in field parasitism rates

Conservation biological control programs advocate the planting of flower strips alongside crops to improve the survival and effectiveness of parasitoids. Ideally, the provided food plants are highly attractive and benefit the targeted biocontrol agents without promoting pests or intraguild competition. Previous laboratory studies showed that Trissolcus basalis, an egg parasitoid of the stink bug Nezara viridula, is highly attracted to floral odors of buckwheat and that its nectar increases the wasp’s fecundity. In the field, T. basalis competes with the co-occurring parasitoid Ooencyrtus telenomicida for host eggs. Therefore, in the present study, we explored whether O. telenomicida shows similar attraction to buckwheat volatiles. We then carried out a 2-year field experiment to assess whether the laboratory-observed olfactory behaviors of both species are reflected in changed parasitism rates of stink bug eggs. Parasitism by naturally occurring egg parasitoids was measured in tomato plots with and without a margin of flowering buckwheat. Our results showed that, unlike T. basalis, O. telenomicida was repelled by the odor of buckwheat flowers. In both years, T. basalis found more egg batches and parasitized more stinkbug eggs when flower margins were present. Egg parasitism correlated positively with proximity to the buckwheat margin. In accordance with our prediction, egg parasitism by O. telenomicida occurred almost exclusively in the control plots and for a shorter period during the season. We conclude that buckwheat strips can influence intraguild competition and hypothesize that the effect was mediated by floral volatiles.

Basil (Ocimum basilicum L.) attracts and benefits the green lacewing Ceraeochrysa cubana Hagen

Aromatic plants can affect arthropod community composition and reduce herbivore populations by attracting beneficial insects such as generalist predators. To investigate the possible mechanisms underlying the attraction of aromatic plant species to natural enemies in the field, we assessed the attractiveness of Ocimum basilicum L. (basil), Mentha piperita L. (peppermint), Melissa officinalis L. (lemon balm) (Lamiaceae) and Cordia verbenacea DC (black sage) (Boraginaceae) to adults of the green lacewing Ceraeochrysa cubana Hagen (Neuroptera: Chrysopidae), a generalist predator widely distributed across the Americas. Additionally, we tested whether access to leaves and flowers of these plant species would affect larval survival, development or oviposition by C. cubana. The green lacewing was attracted to basil but not to the other aromatic plants. Larvae and adults did not benefit from the presence of any plant leaves, but basil flowers enhanced C. cubana larval and adult survival. Basil can be recommended as a companion crop in conservation biological control programs, not only for its well-known negative effects on pests, but also for its attractiveness to generalist predatory insects such as C. cubana. Besides attracting adults, basil flowers benefit both larvae and adults, which is desirable for conservation biological control.

Flowers of Apiaceous species as sources of pollen for adults of Chrysoperla externa (Hagen) (Neuroptera)

The selection of appropriate flowering plants as sources of pollen and nectar for beneficial insect predators and parasitoids is essential in maintaining conservation biocontrol in agroecosystems. The objectives of the present work were: (i) to evaluate the capacity of Chrysoperla externa (Hagen) adults to feed on pollen of three different Apiaceous species (dill, coriander and fennel), and (ii) to evaluate the effects of the provision of Apiaceous flowers on the longevity and reproductive parameters of adult insects under laboratory conditions. C. externa adults (one male and one female) were placed in a polypropylene cage containing a cluster of approximately 200 flowers from one of the three test species, and the oviposited eggs were counted and collected every three days. Egg viability was determined and samples of eggs were used to rear F2 adults. The experiments were conducted at 25±1°C, with 70±10% relative humidity and 12h photoperiod, and ten repetitions were performed for each treatment. The results showed that C. externa adults may survive and reproduce up to the third generation by feeding only on resources provided by flowers of the three Apiaceous species tested. All treatments exerted similar effects on the longevity, duration of preoviposition and oviposition periods, number of eggs/female, number of eggs/female/day and viability of the eggs of F1 insects. The results of this study indicate that dill, coriander and fennel would work well as insectary plants and promote conservation biological control programs aimed at using C. externa to control crop pests.

Experimental evidence that the effectiveness of conservation biological control depends on landscape complexity

Summary The expansion of intensive agricultural practices is a major threat to biodiversity and to the delivery of ecosystem services on which humans depend. Local‐scale conservation management strategies, such as agri‐environment schemes to preserve biodiversity, have been widely adopted to reduce the negative impacts of agricultural intensification. However, it is likely that the effectiveness of these local‐scale management actions depend on the structure and composition of the surrounding landscape. We experimentally tested the utility of floral resource strips to improve local‐scale biological control of crop pests, when placed within a gradient of moderately simple through to highly complex landscapes. We found that experimental provision of floral resources enhanced parasitism rates of two globally important crop pests in moderately simple landscapes but not in highly complex ones, and this translated into reduced pest abundances and increased crop yield. Synthesis and applications. Our results lend experimental support for the ‘intermediate landscape complexity hypothesis’, which predicts that local conservation management will be most effective in moderately simple agricultural landscapes, and less effective in either very simple landscapes where there is no capacity for response, or in highly complex landscapes where response potential is already saturated. This knowledge will allow more targeted and cost‐effective implementation of conservation biological control programs based on an improved understanding of landscape‐dependent processes, which will reduce the negative impacts of agricultural intensification.

How a slow-ovipositing parasitoid can succeed as a biological control agent of the invasive mealybug Phenacoccus peruvianus: implications for future classical and conservation biological control programs

Phenacoccus peruvianus Granara de Willink (Hemiptera: Pseudococcidae) is an invasive mealybug that has become a pest of ornamental plants in Europe and has recently been detected in California, USA. In this work, we studied the tritrophic interaction among this mealybug, its main parasitoid Acerophagus n. sp. near coccois (Hymenoptera: Encyrtidae) and tending ants to disclose the success of this parasitoid controlling P. peruvianus. Acerophagus n. sp. near coccois accepted mealybugs for parasitism regardless of their size but did not host-feed. We recorded three active defenses of P. peruvianus. Host handling time was not influenced by these host defenses but was a time-consuming process that required more than 30 min. Tending ants, Lasius grandis (Hymenoptera: Encyrtidae), reduced the time spent by parasitoids in a patch and disrupted oviposition attempts. The low numbers of ants tending mealybug colonies in Spain and France could explain why this parasitoid, with a long handling time, is an efficient biological control agent for P. peruvianus.

Arthropod fauna of rolled alder leaves in Washington State, United States of America (Insecta, Arachnida)

AbstractThe eastern foothills of the Cascade Range in Washington State, United States of America are west of the State's major fruit-producing region. Alders (Alnus Hill (Betulaceae)), an important floristic component of riparian communities in the Cascade Range foothills, were surveyed for leafrolling caterpillars (Lepidoptera: Tortricidae) that might serve as alternate hosts for parasitoids of orchard pest leafrollers, particularly the nonnative wasp Colpoclypeus florus (Walker) (Hymenoptera: Eulophidae). Tortricid leafrollers were abundant on alder, but reared parasitoids did not include C. florus. Survey results also revealed that rolled leaves were secondarily colonised by a wide variety of predatory and phytophagous arthropods. Rolled leaves were almost 10-fold more likely to be occupied by predatory arthropods than adjacent, roll-free leaves. Phytophagous thrips and mites showed a similar preference for rolled leaves. The most abundant predaceous arthropods in the leafrolls were Anthocoris antevolens White (Hemiptera: Anthocoridae), found in 4.4% of leafrolls, and the spider Clubiona pacifica Banks (Araneae: Clubionidae), found in 8.3% of leafrolls. Both species, and several other predatory insect and spider species found in the rolled leaves, also occur in eastern Washington orchards where they contribute to biological control. Because of its frequent colonisation by beneficial arthropods, alder may prove useful in conservation biological control programs.

Climate change effects on behavioral and physiological ecology of predator–prey interactions: Implications for conservation biological control

Habitat management under the auspices of conservation biological control is a widely used approach to foster conditions that ensure a diversity of predator species can persist spatially and temporally within agricultural landscapes in order to control their prey (pest) species. However, an emerging new factor, global climate change, has the potential to disrupt existing conservation biological control programs. Climate change may alter abiotic conditions such as temperature, precipitation, humidity and wind that in turn could alter the life-cycle timing of predator and prey species and the behavioral nature and strength of their interactions. Anticipating how climate change will affect predator and prey communities represents an important research challenge. We present a conceptual framework—the habitat domain concept—that is useful for understanding contingencies in the nature of predator diversity effects on prey based on predator and prey spatial movement in their habitat. We illustrate how this framework can be used to forecast whether biological control by predators will become more effective or become disrupted due to changing climate. We discuss how changes in predator–prey interactions are contingent on the tolerances of predators and prey species to changing abiotic conditions as determined by the degree of local adaptation and phenotypic plasticity exhibited by species populations. We conclude by discussing research approaches that are needed to help adjust conservation biological control management to deal with a climate future.

Carabidae (Coleoptera) in Nova Scotia, Canada wild blueberry fields: prospects for biological control

AbstractThe Carabidae (Coleoptera) are a diverse family of beetles with almost 300 species identified in Nova Scotia, Canada. Carabid beetle communities have been studied in several agricultural systems, but not wild blueberries, an important crop in eastern Canada. In the interest of potentially developing conservation biological control programs in wild blueberry, we collected Carabidae in crop (fruit-bearing) and sprout (vegetative) blueberry fields in Nova Scotia in order to assess species diversity and abundance over space and time. Over 3200 specimens were collected, representing 51 species. A large portion of collected specimens (39%) were nonnative, and the most abundant species were generally predacious and synanthropic. Species diversity tended to be higher near forest edges than further into fields, but not for all abundant species. Several of the most prominent predators showed significant differences in preference of crop versus sprout fields, distribution throughout fields, and seasonable abundance. These findings have implications for conservation biological control efforts with carabid beetles against several insect pests in wild blueberry.

Effects of floral and extrafloral resource diversity on the fitness of an omnivorous bug, Orius insidiosus

AbstractHabitat manipulation and increasing biodiversity are important approaches that enhance biological control of pests, but it is important to evaluate the relative benefits of specific plant species when designing conservation programs. Orius insidiosus Say (Hemiptera: Anthocoridae) is an important predator of thrips and aphids that also feeds on plants. It is the target of conservation biological control programs. Despite O. insidiosus' relevance, little is known about the effects of plant subsidies on predator performance or nutritional status. Here, we examined the influence of restricting the pollen and nectar resources of five plant species (alyssum, buckwheat, phacelia, fava bean, and chamomile), and how increasing plant diversity affects O. insidiosus fecundity, survival, and nutritional status. Plant species varied in their suitability for O. insidiosus, which was driven in part by the availability of the pollen or nectar resources. Offering plants as a mixture did not improve fecundity; however, the plant least preferred for oviposition under no‐choice tests (fava bean) became the preferred egg‐laying site when the plants were offered in combination. We conclude that the benefits obtained by O. insidiosus vary among plant species, and that increasing plant diversity can have unpredicted, positive effects on insect fitness.

The role of omnivory in the conservation of predators: Orius majusculus (Heteroptera: Anthocoridae) on sweet alyssum

In conservation biological control programs, provision of the required resources (shelter, food, oviposition sites) can be achieved by means of the use of insectary plants. This is especially important in the case of omnivorous predators that feed on prey and plant materials, and where the availability of plant resources plays a significant role in their conservation. An important predator of thrips and other pests in the Mediterranean is the omnivorous bug Orius majusculus (Reuter) (Hemiptera: Anthocoridae). The objective of this study was to evaluate the fertility, fecundity and longevity of O. majusculus on alyssum, (Lobularia maritima L.) with and without prey (Ephestia kuehniella eggs), and compare it with green bean pods. Additionally, the effects of the breeding colony of the individuals on the fertility of O. majusculus were studied. Fecundity on both plants without prey was low; however the addition of prey significantly increased the number of eggs laid, especially on alyssum. The longevity differed significantly among diets, being longer for alyssum with prey eggs. Survival on alyssum without prey was not statistically different from green bean with prey, which shows the potential of alyssum to conserve O. majusculus during times of prey scarcity. The fertility of O. majusculus females was significantly higher on the diets of both plant materials when prey was included. Our results showed that alyssum can provide resource subsidies for O. majusculus during times of prey scarcity in the field.

Tachinidae (Diptera) associated with flowering plants: Estimating floral attractiveness

Non-agricultural flowering plants in agricultural settings provide ecological services, such as nectar-food for adult parasitic flies. In order to determine the attractiveness of flowers to Tachinidae, 12 species of cultivated, introduced/established and native potted plants-in-flower were individually placed beneath interception traps erected along the wooded margins of fields planted seasonally with either feed-corn or rye. Simultaneous controls consisted of traps associated with the same species of plant without flowers, a pot without plants or both. In two additional instances where flowering-plants grew in situ it was necessary to compare initial trap captures to those following the removal of the plants. Of the 14 plant species tested five captured more Tachinidae at the family level than controls (Agastache hybrid, Ageratina aromatica (L.), Aloysia virgata (Lopez & Pavon), Daucus carota L. and Stelleria media (L.)). At the tachinid subfamily and genera/species levels traps associated with Buddleia davidii Franch., Galium aparine L., Agastache hybrid, A. aromatica, A. virgata and D. carota caught significantly more flies than controls. Over all taxonomic levels, half (7) of the plant species-in-flower were associated with trap-catches greater than those associated with plants out-of-flower and/or without plants. There was no relationship between the ratios of flies captured in flowering plant-baited traps relative to those captured in controls and flower widths, flower depths, flower densities, numbers of flowers or floral areas (flower area*number of flowers). However particular plants were identified that might be incorporated into regional conservation biological control programs.

Conserving natural enemies with flowering plants: Estimating floral attractiveness to parasitic Hymenoptera and attraction’s relationship to flower and plant morphology

Flowering plants in agricultural landscapes can provide ecological services, such as nectar-provision for adult parasitic Hymenoptera. Various flowering native, introduced/established and cultivated potted plants were used to bait interception traps along the wooded margins of fields planted seasonally with either feed-corn or rye. Depending on circumstances, controls consisted of traps baited with the same species of plant without flowers, a pot/area without plants, or both. In most cases pots were rotated among trap-sites. Of the 19 plant species tested, 10 captured significantly more summed ichneumonoids and chalcidoids, seven more Braconidae, two more Ichneumonidae and six more Chalcidoidea than controls. Among Braconidae, traps baited with certain plants captured significantly more individuals of specific subfamilies. “Attractive” and “unattractive” plant species tended to cluster in a principal components vector space constructed from plant morphological characteristics (flower width, flower depth, flower density and plant height). Flower width and plant floral-area (flower width 2 * flower density) were the variables that most often explained the variance in capture of the different parasitoid taxa. Our study identified particular plants that could be incorporated into regional conservation biological control programs to benefit parasitoid wasps In addition, the results indicate that morphological characteristics might help identify further suitable plant candidates for agricultural landscape modification.