Conservation Biological Control Strategies Research Articles

Biological Control as Part of the Soybean Integrated Pest Management (IPM): Potential and Challenges

Soybean production is usually performed on large scales, requiring simple but efficient pest management to be successful. Soybean fields are inhabited by several species of arthropods, demanding constant development of management practices to prevent pest outbreaks. More recently, stink bugs have become the most important pest group of soybeans in the Neotropics, responsible for up to 60% of the applied insecticides in Brazil. Natural enemies represent an important mortality factor that can keep the damage caused by stink bugs below the economic threshold levels without additional control actions. Thus, Conservation Biological Control (CBC) strategies can be adopted to preserve or even promote the increase in such natural enemies in the fields, or alternatively, massive releases of biocontrol agents in Augmentative Biological Control (ABC) programs could be adopted. Simple practices such as reducing insecticide use (with the adoption of economic thresholds), prioritizing harmless insecticides or biopesticides, and planting resistant soybean cultivars have been adopted in Brazil with positive results. The challenges to increasing the adoption of more complex stink bug management in commodity crops such as soybean may be overcome using the more recent economic incentives in the global agenda of decarbonized agriculture. The potential and challenges of conservation and augmentative biological control are further discussed in this review.

Tomato Potato Psyllid Bactericera cockerelli (Hemiptera: Triozidae) in Australia: Incursion, Potential Impact and Opportunities for Biological Control.

Incursion and establishment of an exotic pest may threaten natural habitats and disrupt ecosystems. On the other hand, resident natural enemies may play an important role in invasive pest control. Bactericera cockerelli, commonly known as the tomato-potato psyllid, is an exotic pest, first detected on mainland Australia in Perth, Western Australia, in early 2017. B. cockerelli causes direct damage to crops by feeding and indirectly by acting as the vector of the pathogen that causes zebra chip disease in potatoes, although the latter is not present in mainland Australia. At present, Australian growers rely on the frequent use of insecticides to control B. cockerelli, which may lead to a series of negative economic and environmental consequences. The incursion of B. cockerelli also provides a unique opportunity to develop a conservation biological control strategy through strategically targeting existing natural enemy communities. In this review, we consider opportunities to develop biological control strategies for B. cockerelli to alleviate the dependence on synthetic insecticides. We highlight the potential of existing natural enemies to contribute toward regulating populations of B. cockerelli in the field and discuss the challenges ahead to strengthen the key role they can play through conservation biological control.

Aphid Pest Management in Sweet Pepper Field with Rapeseed as a Companion Crop

Sweet pepper, Capsicum annum L. is commercially grown vegetable grown for its nutritional and economical value. Sucking pests like aphids, whiteflies, thrips, mites, etc. are the major insect pest in sweet pepper fields. Farmers deliberately have been using chemical pesticides in their crop to manage various insect pest and such practices of using hazardous chemicals are harmful to human health and the biodiversity. Similarly, farmers don't have an idea of planting trap and/or companion plants and its role in natural control of pest. Hence, a study was conducted to know the population dynamics, especially to assess the aphid (Myzus persicae, Sulzer) population and its potential natural enemies by planting rapeseed as companion crop. This field experiment was conducted in six different locations of Bharatpur-23, Chitwan from Nov 2019 to Jan 2020 where three plots of sweet pepper were planted with rapeseed as companion crop and other three plots solely having no floral source around. Aphid population was recorded at weekly interval and its major natural enemies; ladybird beetle and syrphid fly. Abnormal data were squared root transformed and analyzed by using paired sample t-test. The result showed that the aphid population in sweet pepper field with companion crop was significantly lower than in sweet pepper grown without floral source (control). Highly significant number of ladybird beetles and syrphid flies were recorded in sweet pepper with companion crop compared to control. The finding is helpful to develop an integrated management protocol of sweet pepper pests with the practice of following conservation biological control strategy.

Dietary sugars and amino acids increase longevity and enhance reproductive parameters of Bracon cephi and B. lissogaster, two parasitoids that specialise on wheat stem sawfly

AbstractThe wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a major pest of wheat grown on the Northern Great Plains and Canadian Prairies of North America, causing economic losses of as much as $350 million annually. Two species that parasitize wheat stem sawfly larvae in wheat stems are Bracon cephi (Gahan) and B. lissogaster Muesebeck (Hymenoptera: Braconidae). Carbohydrate‐rich diets increase adult parasitoid longevity and reproductive parameters, enhancing their success as natural enemies. In previous studies, these species had increased longevity, egg load, and volume when fed sucrose solutions, encouraging further research on their nutritional needs. Therefore, we conducted experiments with artificial diets using adult females fed sucrose, glucose, and fructose solutions. Females were also fed these sugars in combination with a mixture of amino acids. We assessed individuals daily for longevity. Both species benefited from diets containing carbohydrates, with an increase in longevity from an average of 9 to 51 days for B. cephi, and from 6 to 34 days for B. lissogaster. Additional experiments assessed egg load and volume after 2, 5, and 10 days of cumulative feeding in B. cephi. These females produced 1.4‐fold more eggs when fed amino acids, 2.5‐fold more with sugar, and 2.7‐fold more when fed sugar with amino acids. They had a 1.3‐fold increase in egg volume when fed amino acids, 1.9‐fold with sugar, and 2.1‐fold when fed sugar with amino acids. Our study reveals the nutritional requirements of these braconid parasitoids and the benefits of nutritional sources when implementing conservation biological control strategies.

Field margins and botanical insecticides enhance Lablab purpureus yield by reducing aphid pests and supporting natural enemies.

Botanical insecticides offer an environmentally benign insect pest management option for field crops with reduced impacts on natural enemies of pests and pollinators while botanically rich field margins can augment their abundance. Here, we evaluated the non‐target effects on natural enemies and pest control efficacy on bean aphids in Lablab of three neem‐ and pyrethrum‐based botanical insecticides (Pyerin75EC®, Nimbecidine® and Pyeneem 20EC®) and determine the influence of florally rich field margin vegetation on the recovery of beneficial insects after treatment. The botanical insecticides were applied at the early and late vegetative growth stages. Data were collected on aphids (abundance, damage severity and percent incidence) and natural enemy (abundance) both at pre‐spraying and post‐spraying alongside Lablab bean yield. The efficacy of botanical insecticides was similar to a synthetic pesticide control and reduced aphid abundance by 88% compared with the untreated control. However, the number of natural enemies was 34% higher in botanical insecticide‐treated plots than in plots treated with synthetic insecticide indicating that plant‐based treatments were less harmful to beneficial insects. The presence of field margin vegetation increased further the number of parasitic wasps and tachinid flies by 16% and 20%, respectively. This indicated that non‐crop habitats can enhance recovery in beneficial insect populations and that botanical insecticides integrate effectively with conservation biological control strategies. Higher grain yields of 2.55–3.04 and 2.95–3.23 t/ha were recorded for both botanical insecticide and synthetic insecticide in the presence of florally enhanced field margins in consecutive cropping seasons. Overall, these data demonstrated that commercial botanical insecticides together with florally rich field margins offer an integrated, environmentally benign and sustainable alternative to synthetic insecticides for insect pest management and increased productivity of the orphan crop legume, Lablab.

Success stories in biological control: Lessons learnt

Globally, several success stories have been documented on classical, augmentative and conservation biological control strategies for managing insect pests and weeds. India too has had its share of successes in the field of biological control. Some examples include the management of the papaya mealy bug through classical biological control, suppression of the sugarcane woolly aphid through conservation biological control, and management of rice pests through augmentation biological control. However, it is a sad state of affairs that biocontrol practices have not been either universally accepted or optimally utilised as per the expectations. There are several hurdles to the uptake of biological control, which include unwieldy regulatory procedures to be followed for international exchange of biocontrol agents and registration of microbial biopesticides; hesitation amongst the commercial units to take up production of biocontrol agents (macrobials and microbials) and lack of active interactions between biocontrol researchers and all other stake-holders including farmers, public, extension workers, regulators and politicians. In this paper, an attempt has been made to compile information on some of the significant success stories in the field of biological control. Based on the lessons learnt from the older biological control success stories, proactive steps have been taken in India to tackle some of the recent invasive pests. The need of the hour is for biocontrol researchers and practitioners to network with economists, social scientists and other relevant stakeholders so that the social, economic and financial value of biological control (primarily based on the success stories) can be clearly defined and accurately quantified and communicated to farmers, commercial units and policymakers, which can lead to increased uptake of this sustainable method of pest management.

Occurrence of soil-inhabiting entomopathogenic fungi within a conventional and organic farm and their virulence against Spodoptera litura

Abstract. Afandhi A, Choliq FA, Fernando I, Marpaung YMAN, Setiawan Y. 2022. Occurrence of soil-inhabiting entomopathogenic fungi within a conventional and organic farm and their virulence against Spodoptera litura. Biodiversitas 23: 1172-1180. Naturally occurring entomopathogenic fungi (EPF) are important components in agroecosystems as they serve as biocontrol agents of insect and mite pests. However, some cultivation practices may have deleterious effects on EPF. In this study, the occurrence of soil-inhabiting EPF was investigated between a conventional and organic farm. EPF was baited using Tenebrio molitor larvae, and their virulence was tested against Spodoptera litura larvae. The results showed a higher occurrence of EPF in the organic farm than the conventional farm, with Aspergillus sp., Beauveria sp., and Gliocladium sp. were exclusively found in organic soils. Among the twenty-five EPF isolates obtained, only four isolates were avirulent against S. litura larvae. Isolates belonging to Beauveria, Metarhizium, and Paecilomyces genera caused high mortality of S. litura larvae ranging from 40 to 65%. There was a significant positive relationship between the conidial viability of EPF and larval mortality. Since virulent isolates were found in conventional soils, efforts in preserving EPF prevalence are needed through the implementation of appropriate cultivation practices. The synthetic agrochemicals exclusion, organic fertilizers application, and crop rotation practiced in the organic farm should be integrated into any other agroecosystems as a form of conservation biological control strategies to strengthen the pest control service provided by EPF.

Airborne pollen can affect the abundance of predatory mites in vineyards: implications for conservation biological control strategies.

BACKGROUNDThe importance of pollen as alternative food for generalist phytoseiid mites occurring in vineyards has been investigated in northeastern Italy. We compared pollen and phytoseiid abundance in four vineyards and in plots located at different distance from flowering hop plants. Pollen (Carpinus betulus and Typha spp.) was sprayed onto the foliage to evaluate the potential impact of this food source on predatory mite abundance. Finally, grass management was investigated to analyze the effect of a reduced mowing frequency on predatory mite population densities.RESULTSArboreal pollen was found mostly during the spring and the grapevine blossoming period. Nonarboreal pollen dominated throughout the growing seasons. In vineyards, the abundance of Amblyseius andersoni, Kampimodromus aberrans, Phytoseius finitimus, Typhlodromus pyri eggs and motile forms increased after a phase of large pollen availability. Hop pollen promoted K. aberrans population increases in vineyards. Pollen applications increased predatory mite egg and motile form densities and similar effects were obtained by reducing mowing frequency in vineyards.CONCLUSIONPollen availability positively affects the biology of four phytoseiid species, promoting stable predatory mite populations in vineyards. However, natural pollen availability and predatory mite abundance often decrease in summer, and pollen supply can mitigate this trend. A higher pollen availability could be guaranteed by inserting hedges comprising species having scalar bloom, reducing mowing of inter‐row groundcover and spraying pollen. The presence of flowering plants surrounding vineyards and in their inter‐rows should be considered as a relevant factor to enhance the success of biocontrol tactics against phytophagous mites in viticulture.

Conservation of Non-Pest Whiteflies and Natural Enemies of the Cabbage Whitefly Aleyrodes proletella on Perennial Plants for Use in Non-Crop Habitats

Simple SummaryThe cabbage whitefly Aleyrodes proletella is a major insect pest of many cabbage crops. Natural enemies, in particular Encarsia tricolor as well as different hoverfly larvae and spiders, do not decrease pest populations sufficiently. The objective of this study is to promote local natural enemy populations by permanently establishing a non-pest whitefly species, which is an alternative host and additional food source when A. proletella is scarce or even absent. Therefore, the perennial abundance of the non-pest honeysuckle whitefly Aleyrodes lonicerae and natural enemies on different plants were evaluated in the open field. Wood avens Geum urbanum was the best host plant for A. lonicerae in terms of reproduction and overwintering. Most E. tricolor and spiders were also found on this plant species. In the future, G. urbanum might be used in non-crop habitats to increase natural enemy abundances in the agricultural landscape and decrease damage caused by A. proletella on adjacent cabbage plants.Aleyrodes proletella causes severe economic damage to several Brassica crops. Its naturally occurring enemies often immigrate late in the season or appear in low numbers on cabbage. This field study aims to permanently increase the local abundance of A. proletella’s natural enemies by providing the non-pest whitefly Aleyrodes lonicerae as an alternative and overwintering host/prey. Therefore, the population dynamics of natural enemies on different perennial herbaceous plants pre-infested with A. lonicerae were determined at two field locations over two winter periods. Most A. lonicerae colonized (on average 166.22 puparia per m²) and overwintered (342.19 adults per m²) on wood avens Geum urbanum. Furthermore, the abundance of A. proletella main parasitoid Encarsia tricolor (28.50 parasitized puparia per m²) and spiders (12.13 per m²) was 3–74 times and 3–14 times higher, respectively, on G. urbanum compared to the other experimental plants. Conclusively, G. urbanum pre-infested with A. lonicerae permanently promoted natural enemies of A. proletella by serving as shelter, reproduction, and overwintering habitat. A potential implementation of G. urbanum in conservation biological control strategies (e.g., tailored flower strips, hedgerows) against A. proletella are discussed and suggestions for future research are given.

The interplay between mutualism, competition and dispersal promotes species coexistence in a multiple interactions type system

The stability and maintenance of species biodiversity in the multiple interactions type systems have attracted much attention. Regardless of their nature, several forms of interactions are discovered to exhibit oscillatory behaviour. This large-amplitude oscillation also de-stabilizes populations of multiple species and raises species’ chances of extinction. A central question in ecology is how do we maintain community stability and species coexistence mechanisms in a multiple interactions type community. It is thought that the dynamics of mutualism support multi-species coexistence in a complex ecological system. Here, we extend a four-species multiple interactions type (e.g., resource-competitor-exploiter-mutualist) system by incorporating a local dispersal component. We then employ this model to assess how the combined impacts of dispersal, mutualism and competition shape species coexistence and community stability in this ecological system. Our findings show that the interplay of mutualism and competition affects the complexity of ecological dynamics in this multiple interactions type system with local dispersal. Using numerical simulation, we demonstrate how strong mutualism could stabilize the spatio-temporal dynamics. Employing bifurcation analysis, we also discover that mutualism essentially modifies this ecological community’s response to increasing competitive pressure on the resource species. These insights are evident in our findings through the emergence of intriguing dynamics where stable limit cycles alternate with unstable ones as competitive pressure varies. While alternative stable states are common in different ecological systems with mutualistic interactions, they are often stable, whereas, in our studies, we realize that there can be alternative stable or unstable states if the spatial dimension is considered through the incorporation of the diffusion component. Consequently, the long-term dynamics converge to multi-species coexistence outcomes either via a stable steady state or a limit cycle depending on species’ initial abundances. It is also observed that this complexity ceases when mutualism becomes strong enough. Additionally, the destabilization of species biodiversity phenomenon through the occurrence of limit cycles increasing in the amplitude of oscillations (with some species population densities approaching zero) is weakened in the presence of strong mutualistic strength and local dispersal. Overall, the joint effects of mutualism, competition and local dispersal result in different community compositions, and these insights may have significant consequences in conservation management and biological control strategies.

A novel approach to quantifying trophic interaction strengths and impact of invasive species in food webs

Measuring ecological and economic impacts of invasive species is necessary for managing invaded food webs. Based on abundance, biomass and diet data of autochthonous and allochthonous fish species, we proposed a novel approach to quantifying trophic interaction strengths in terms of number of individuals and biomass that each species subtract to the others in the food web. This allowed to estimate the economic loss associated to the impact of an invasive species on commercial fish stocks, as well as the resilience of invaded food webs to further perturbations. As case study, we measured the impact of the invasive bass Micropterus salmoides in two lake communities differing in food web complexity and species richness, as well as the biotic resistance of autochthonous and allochthonous fish species against the invader. Resistance to the invader was higher, while its ecological and economic impact was lower, in the more complex and species-rich food web. The percid Perca fluviatilis and the whitefish Coregonus lavaretus were the two species that most limited the invader, representing meaningful targets for conservation biological control strategies. In both food webs, the limiting effect of allochthonous species against M. salmoides was higher than the effect of autochthonous ones. Simulations predicted that the eradication of the invader would increase food web resilience, while that an increase in fish diversity would preserve resilience also at high abundances of M. salmoides. Our results support the conservation of biodiverse food webs as a way to mitigate the impact of bass invasion in lake ecosystems. Notably, the proposed approach could be applied to any habitat and animal species whenever biomass and diet data can be obtained.

Spatiotemporal dynamics of active flying Diptera predators among different farmland habitats

Farmland habitats comprise an arrangement of cropped, uncropped and natural vegetation among the farms. Despite the differences in these habitats' features, generalist highly mobile predators are more likely to explore them in time and space. We investigated the spatiotemporal dynamics of the species of Dolichopodidae (Diptera) in organic vegetable farms because they are one of the most abundant generalist highly mobile predators in Brazilian agroecosystems. We simultaneously sampled the abundance of Condylostylus Bigot and Chrysotus Loew adults (both Dolichopodidae) in the crop, fallow areas, agroforests and forest fragments within five organic farms for 2 years. Predators preferred open‐field habitats to agroforests and forest fragments. Probably, open‐field habitats present more opportunities to prey foraging, resulting in higher population densities. To the extent that abiotic conditions become more restrictive during the dry season, agroforests and forests act as breeding sites and shelter, thereby maintaining the predators' populations in the overall farmland habitat. Both predatory genera occupy habitats with distinct features across time, forming a dynamic and contiguous population unit within the farm. Therefore, conservation biological control strategies in organic crops should consider the role of agroforests and forest fragments in species conservation beyond the plot level.

Semiochemicals and habitat manipulation to support green lacewing activity to reduce aphid infestations in agroecosystems

Conservation biological control (CBC) is a promising tool for ecological intensification that aims to establish resilient natural enemy populations that contribute to pest management with reduced use of pesticides and at the same time support native biodiversity in agroecosystems. Yet the impact of natural enemies in CBC is often limited due to missing resources such as food, habitat, and hibernation shelters. Here, we studied a CBC strategy that incorporates these essential resources combined with semiochemicals, focusing on how the common green lacewing can enhance biological control of aphids.In a 4-year field study conducted at three locations in the region of East Norway, we developed a CBC strategy combining the three measures ATTRACT (a ternary attractant that increase lacewing egg laying), FOOD (floral buffer strips), and SHELTER (insect hotels for overwintering survival) to increase aphid biological control in spring barley. We recorded the number of lacewings, ladybirds, hoverflies, parasitized aphid mummies, and the two cereal aphid species Sitobion avenae and Rhopalosiphum padi. Our CBC strategy resulted in a significant increase in lacewing activity and significant aphid suppression. At all three locations and over the 4-year period, aphid infestation was below the economic damage threshold in the field plots using CBC measures. In contrast, during two of the years, the density of the aphid infestation in the control plots was significantly above the damage threshold. We found evidence that use of the ternary attractant supported green lacewings but led to loss of ladybirds, hoverflies, and parasitoids, even though flower strips were used as alternative resources.Our study shows a promising increase in lacewing activity in the agricultural landscape and high biological control of aphids in barley. Long-term field studies are needed to evaluate the impact on non-target species and the agroecosystem before practical application of this approach can be considered.

Local dispersal, trophic interactions and handling times mediate contrasting effects in prey-predator dynamics

Trophic interactions between prey and predator species are an ubiquitous force in nature and it is reckoned to be one of the most important factors that can shape species geographical range limits. To better understand how local dispersal and predator handling times affect community dynamics, we perform a bifurcation analysis of a partial differential equations model consisting of environmental gradients, trophic (generalist, specialist predator and prey species) interactions and spatial diffusion components. Our co-dimension one bifurcation results depict the existence of numerous threshold values corresponding to supercritical and subcritical Hopf bifurcations, saddle-node bifurcation of cycles and transcritical bifurcation, as the magnitude of handling times and the generalist predation-induced mortality force change in this ecological system with local dispersal. It is discovered that the interaction between these distinct local bifurcations leads to higher codimension (two) bifurcation such as a generalised Hopf bifurcation, which acts as an organising centre of the dynamics. Ecologically, we also observe that: (i) without dispersal, higher levels of generalist predation (which acts as a mortality agent) require shorter specialist predator handling times to promote the maintenance of biodiversity through coexistence steady state of prey-predator species and oscillatory dynamics; however, lower forces of generalist predation result in longer specialist predator handling times and this situation induces destabilisation of species biodiversity; (ii) local dispersal stabilises the trophic dynamics and mediates more species diversity outcomes; (iii) dispersal interacts with lower magnitudes of generalist predator-induced mortality to generate bistability phenomenon between stable limit cycles and coexistence steady state; (iv) interestingly, higher intensities of mortality factor combined with dispersal may destroy some interior attractors, and exclude bistability-oscillatory dynamics in this trophic system; consequently, this situation leads to the extinction of specialist predator species and jeopardises species biodiversity. Taken together, our findings illustrate the influential roles of local dispersal, trophic interactions and handling times in determining community dynamics and these insights may have important consequences in conservation management and biological control strategies.

Aphid predators in citrus crops: the least voracious predators are the most effective

Rich and abundant predator complexes are frequently associated with aphids in perennial agroecosystems. The ability of these predators to successfully suppress aphid populations is nevertheless highly variable. The development of operative conservation biological control strategies is mostly hindered by the lack of knowledge of the specific roles of the aphidophagous assemblage components, their intra-guild relationships and the predatory attributes that chiefly determine their effectiveness. The role of predation in the biological control of aphids in perennial agroecosystems was assessed through exclusion experiments in aphid infested citrus crops. Important predator attributes such as recruitment, aphid consumption rates, and foraging strategies were related to their efficacy. Predation greatly affected aphid colony phenology as well as size. Predators with lower aphid consumption rates (Micro-coccinellid species and Cecidomyiidae) were revealed to be the most efficient aphidophaga. These predators encountered aphid colonies at earlier colony stages and significantly reduced their population growth rates. Later more voracious aphidophaga groups (Chrysopidae and Macro-coccinellids) did not present effective biological control of the colonies. Contrarily to what was widely believed, the less voracious aphidophaga groups such as the Micro-coccinellids and Cecidomyiids are probably the groups who are mostly responsible for aphid suppression. Future conservation biological control studies in this crop should therefore chiefly focus on these groups.

Brazilian Legislation Leaning Towards Fast Registration of Biological Control Agents to Benefit Organic Agriculture.

Brazil is one of the main users of chemical pesticides in the world. These products threaten human and environmental health, and many of them are prohibited in countries other than Brazil. This paradigm exists in contrast with worldwide efforts to make the need for food production compatible with biodiversity conservation, preservation of ecosystem services, and human health. In this scenario, the development of sustainable methods for crop production and pest management such as organic agriculture and biological control are necessary. Herein, we describe how the process of registration of natural enemy-based products in organic agriculture is simpler and faster than the conventional route of chemical insecticides and can favor the development of the biological control market in Brazil. Since the regulatory mechanisms have been established in Brazil for organic agriculture, the number of biological control products registered has increased exponentially. Today, 50 companies and associations are marketing 16 species/isolates and 95 natural enemy-based products. Although this scenario presents a series of new opportunities to increase and stimulate a more sustainable agriculture in the country, biological control is not always aligned with the aims and philosophy of organic agriculture and agroecology. Therefore, we also argue that new research efforts are needed on understanding how conservation biological control strategies can be integrated with augmentation biological control to promote a sustainable agriculture under the concepts of organic agriculture and agroecology.

Exogenous application of the plant signalers methyl jasmonate and salicylic acid induces changes in volatile emissions from citrus foliage and influences the aggregation behavior of Asian citrus psyllid (Diaphorina citri), vector of Huanglongbing.

Huanglongbing, also known as citrus greening, is a destructive disease that threatens citrus production worldwide. It is putatively caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (Las). Currently, the disease is untreatable and efforts focus on intensive insecticide use to control the vector, Asian citrus psyllid (Diaphorina citri). Emerging psyllid resistance to multiple insecticides has generated investigations into the use of exogenously applied signaling compounds to enhance citrus resistance to D. citri and Las. In the present study, we examined whether foliar applications of methyl jasmonate (MJ), a volatile signaling compound associated with the induced systemic resistance pathway, and salicylic acid, a constituent of the systemic acquired resistance pathway, would elicit the emission of defense-related volatiles in citrus foliage, and what effect this might have on the host-plant searching behavior of D. citri. Comparisons were made of volatiles emitted from growing shoots of uninfected and Las-infected ‘Valencia’ sweet orange (Citrus sinensis) trees over two consecutive sampling days. A settling behavioral assay was used to compare psyllid attraction to MJ-treated vs. Tween-treated citrus sprigs. All three main effects, Las infection status, plant signaler application, and sampling day, influenced the proportions of individual volatile compounds emitted in different treatment groups. MJ- and SA-treated trees had higher emission rates than Tween-treated trees. Methyl salicylate (MeSA) and β-caryophyllene were present in higher proportions in the volatiles collected from Las-infected + trees. On the other hand, Las-infected + MJ-treated trees emitted lower proportions of MeSA than did Las-infected + Tween-treated trees. Because MeSA is a key D. citri attractant, this result suggests that MJ application could suppress MeSA emission from Las-infected trees, an approach that could be used to discourage psyllid colonization during shoot growth. MJ application enhanced emission of E-β-ocimene, indole, volatiles attractive to many of the psyllid’s natural enemies, indicating that MJ application could be used in an ‘attract and reward’ conservation biological control strategy. Volatile emissions in SA-treated trees were dominated by MeSA. MJ application elicited aggregation behavior in D. citri. Similar numbers of psyllids settled on MJ-treated versus Tween-treated sprigs, but a significantly greater percentage of the MJ-treated sprigs had aggregations of nine or more psyllids on them. Taken together, the results of this study indicate that exogenous applications of MJ or SA could be used to influence Asian citrus psyllid settling behavior and attract its natural enemies.

Bactrocera oleae pupae predation by Ocypus olens detected by molecular gut content analysis

The pupae of Bactrocera oleae (Diptera: Tephritidae) complete their development during autumn and winter in the soil, rather than in the drupe, resulting susceptible to edaphic predators. Environmentally friendly methods to control this olive pest involve the identification of its natural enemies. This study evaluated the role of Ocypus olens (Coleoptera: Staphylinidae) in the predation of B. oleae pupae, by means of molecular gut content analysis. Modified dry pitfall traps were used to collect live specimens from low-input olive orchards in Tuscany (Italy). Sampling was fine-tuned with a degree-day model estimating the presence of pest pupae in the soil. PCR analyses carried out on field-collected specimens demonstrated that O. olens is a predator of B. oleae, at least during autumn. These results are consistent with predictions of the degree-day model. Knowledge on species composition, traits and complementarity of the natural enemies of B. oleae pupae needs further investigation to advance conservation biological control strategies.

Cucumber Plants Baited with Methyl Salicylate Accelerates Scymnus (Pullus) sodalis (Coleoptera: Coccinellidae) Visiting to Reduce Cotton Aphid (Hemiptera: Aphididae) Infestation

The cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae), is a major pest of many crops worldwide and a major cucumber plant pest in Taiwan. Because cotton aphids rapidly develop insecticide resistance and because of the insecticide residue problem, a safe and sustainable method is required to replace conventional chemical control methods. Methyl salicylate (MeSA), a herbivore-induced plant volatile, has been shown to affect aphids' behavior and attract the natural enemies of aphids for reducing their population. Therefore, this study examined the direct effects of MeSA on cotton aphids' settling preference, population development, and attractiveness to natural enemies. The efficiency of using MeSA and the commercial insecticide pymetrozine for reducing the cotton aphid population in laboratory and outdoor cucumber plant pot was also examined. The results showed no difference in winged aphids' settling preference and population development between the MeSA and blank treatments. Cucumber plants infested with cotton aphids and baited with 0.1% or 10% MeSA contained significantly higher numbers of the natural enemy of cotton aphids, namely Scymnus (Pullus) sodalis (Weise) (Coleoptera: Coccinellidae), and MeSA-treated cucumber plants contained a lower number of aphids. Significantly lower cotton aphid numbers were found on cucumber plants within a 10-m range of MeSA application. In addition, fruit yield showed no difference between the MeSA and pymetrozine treatments. According to our findings, 0.1% MeSA application can replace insecticides as a cotton aphid control tool. However, large-scale experiments are necessary to confirm its efficiency and related conservation biological control strategies before further use.

Wild flower resources and insect honeydew are potential food items for Elasmus flabellatus

Adult parasitoids need non-host food such as nectar or honeydew for survival and reproduction. In a conservation biological control strategy, the knowledge about non-host feeding of parasitoid species is a key factor to successfully increase their action. The nutritional behavior of Elasmus flabellatus (Fonscolombe) (Hymenoptera: Eulophidae), a major parasitoid of the olive moth, Prays oleae (Bernard) (Lepidoptera: Praydidae), is completely unknown. Survival experiments were performed on two secondary olive pest honeydews and eight common flowering plant species in order to analyze their suitability as potential food sources for E. flabellatus females. Abdomen and gut dissections were carried out to verify the pollen consumption and the egg production. Floral architecture and insect morphology were described. Cox’s proportional hazard regression models were used to analyze the differences between parasitoid survivals. Honeydews secreted by Saissetia oleae (Olivier) (Hemiptera: Coccidae) and Euphyllura olivina (Costa) (Hemiptera: Psyllidae) resulted in the best performance followed by the flowers of Malva sylvestris L. (Malvaceae), Daucus carota L. (Apiaceae), and the Cichorioideae Tolpis barbata (L.) and Andryala integrifolia L. Theoretical flower resources accessibility were assessed and related with the survival results. E. flabellatus females did not consume pollen and did not produce eggs, suggesting that the species is synovigenic and requires additional foods for egg production. In sustainable pest control programs, this novel knowledge is a promising opportunity for improving suitable food resources of E. flabellatus in the field.