Augmentative Biological Control Research Articles

First record of a new microsporidium pathogenic to Gonipterus platensis in Brazil

Microsporidia are naturally occurring fungal-related parasites that can infect nearly all animal hosts, but their biocontrol potential of insect pests is routinely overlooked in agriculture and forestry. This research brings the first report describing the natural occurrence of a microsporidium causing disease in field-collected populations of the invasive eucalyptus snout beetle, Gonipterus platensis (Coleoptera: Curculionidae), a major destructive pest of eucalyptus plantations in Brazil. Adult beetles were collected during field surveys in commercial eucalyptus plantations in southern Brazil to be examined and dissected with typical symptoms to verify presence of microsporidian spores in haemolymph. From 14 plantations in different sites, the natural infection occurrence in these populations ranged from 0 to 65%, while a lab colony exhibited an infection incidence of 70%. Spore density in haemolymph of symptomatic insects averaged 2.1 (± 0.4) × 107 spores/beetle. Symptoms in infected adults were identified by an abnormal abdomen with malformation of the second pair of wings, impairing their flight activity. Electron transmission microscopy of the pathogen showed morphological features similar to species belonging to the genus Nosema or Vairimorpha. Phylogenetic analysis of the full-length small subunit ribosomal RNA gene suggests this pathogen’s placement in the genus Vairimorpha, but with a sequence identity of ~ 94% with the nearest neighbours. The low level of sequence identity suggests this pathogen may represent a novel taxon in the genus and further requires whole genome sequencing for definitive taxonomic resolution. These findings provide insights on the natural occurrence of this novel pathogen of this invasive pest in Eucalyptus plantations in Brazil. Further studies are needed to determine potential of this microsporidium in the design of conservative or augmentative biological control programs for this invasive pest.

Male Impact on Female Reproductive Performance of the Larval Tephritid Parasitoid Diachasmimorpha tryoni (Hymenoptera: Braconidae).

Diachasmimorpha tryoni (Cameron) (Hymenoptera: Braconidae) is a larval parasitoid that has been mass-reared for augmentative biological control against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in Hawaii and other regions. To improve performance of female wasps in biological control programs, we conducted a series of experiments to investigate male wasp reproductive performance and its role in female reproductive success. The results showed that D. tryoni males remained close to the emergence (release) site following release. Males emerged earlier than females and male's capacity to inseminate females reached the highest level (inseminated 9.2 ± 0.4 females/day) on the second day after eclosion in synchronization with female emergence peak; allowing males encountering most receptive females to enhance their mating success. Mating rates under normal rearing conditions (200 pairs per cage) reached optimum 100% insemination after 5 d. However, oviposition experience prior to mating impaired female's receptivity as a percentage of inseminated females reduced to 17.5 ± 4.8%, while 70.0 ± 4.1% females without prior oviposition experience accepted mating. Mating reduced male's survivorship and the potential lifetime fecundity of females, although multiple mating increased percentage of female offspring. Overall, influence of male density on the female oviposition rate and offspring sex ratio was not detected under captive rearing conditions. These results suggest that local and early mating is important for male's reproductive success and females must be allowed to mate before they are exposed to hosts or released in the field to achieve their full reproductive potential.

Adding a Natural Enemy to Respond to Pest Immigration and Delayed Natural Enemy Releases in Augmentative Biological Control.

Whether increased natural enemy density or adding a second natural enemy species will provide superior pest suppression in greenhouse augmentative biological control is unknown for many commercially available natural enemy species. In this study, we use sweetpotato whiteflies, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), on poinsettias, Euphorbia pulcherrima Willd. ex Klotzsch (Malpighiales: Euphorbiaceae), to determine whether adding Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) to Eretmocerus eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae) is better for B. tabaci suppression compared with either natural enemy alone, both with and without challenges with whitefly immigration or delayed natural enemy releases. The number of whiteflies on caged poinsettias treated with different natural enemy release rates (single or double rate), natural enemy species (one or two species), natural enemy delayed release (weeks 4 and 8), and whitefly immigration treatments (introduced at week 4 or week 8) was censused biweekly for 16 wk. Both species used in combination provided similar or better suppression of whiteflies compared with either natural enemy alone. Both species combined also provided superior suppression of whiteflies when challenged with whitefly immigration or delays in natural enemy releases compared with E. eremicus alone. Whitefly immigration or delays in E. eremicus releases did not increase whitefly populations, suggesting that suppression of whiteflies by E. eremicus alone is relatively robust. This study found no evidence for negative interactions between E. eremicus and A. swirskii for suppressing B. tabaci.

Intrinsic Interspecific Competition Between Telenomus podisi and Trissolcus teretis (Hymenoptera: Scelionidae).

The competition between Telenomus podisi Ashmead and Trissolcus teretis (Johnson) parasitizing eggs of Diceraeus melacanthus (Dallas) and Euschistus heros (Fabricius) was studied in three different laboratory bioassays to gather knowledge in order to improve stink bug management and to strengthen the preservation of naturally occurring parasitoid species. The impact of parasitoid sequence and time intervals (4 to 192 h) between parasitoid species was evaluated. Competition of Te. podisi and Tr. teretis for the same host favored the parasitoid encountering the egg host first, as it usually outcompetes the second parasitoid. We conclude that it is unwarranted in a short-term goal to release both species together in augmentative biological control programs since the repeated release of Te. podisi led to higher parasitism than any other studied variation of parasitoid sequence. However, simultaneous release of multiple species could be important to help the preservation of the diversity of scelionids in the agroecosystem, a hypothesis that needs to be further investigated in future research.

Aphidophagous hoverflies reduce foxglove aphid infestations and improve seed set and fruit yield in sweet pepper

Larvae of many hoverfly species prey upon aphids, whereas the adults, by relying on nectar and pollen, contribute to the pollination of many plant species. Despite their great potential for pest control and pollination, important gaps still exist regarding the efficacy of hoverflies in regulating infestations of major aphid pests in augmentative biological control programs. Here, we tested the potential of the commercially available hoverflies Eupeodes corollae and Sphaerophoria rueppellii to regulate populations of the foxglove aphid Aulacorthum solani in sweet pepper. In a semi-field experiment, aphid numbers were 93.2% and 78.4% lower in the E. corollae and S. rueppellii treatments, respectively, compared to the control. Fruit yield was increased by 390% and 361% and seed set by 395% and 399% for E. corollae and S. rueppellii. In a separate laboratory trial, we found that under conditions of limited prey, hoverfly larvae did not complete development, but that larvae of S. rueppellii survived significantly longer than larvae of E. corollae. We have shown for the first time that E. corollae and S. rueppellii can reduce infestations of foxglove aphid in sweet pepper. The limited amount of prey, related to the small size of the A. solani colonies, means that hoverfly larvae were often not able to complete development. In practice, repeated releases of hoverflies, possibly in combination with other natural enemies, might be used to achieve effective suppression of A. solani infestations. © 2021 Society of Chemical Industry.

Recent advances in the biological control of citrus nematodes: A review

Parasitic nematodes including Tylenchulus semipenetrans, Radopholus similis, Pratylenchus coffeae and Meloidogyne spp. are significant pests of citrus worldwide. Various microbes and soil-dwelling predatory mites (Acari: Mesostigmata) have been evaluated as augmentative biological control agents against citrus parasitic nematodes. Some microbial candidates have received attention as bionematicides with reduced environmental toxicity. They include fungi (Trichoderma spp., Purpureocillium lilacinum, Pochonia chlamydosporia, and mycorrhizae, Glomus spp.) and bacteria (Bacillus spp., Pseudomonas fluorescens, Streptomyces avermitilis, and Pasteuria spp.), that have been applied against nematodes parasitic in different citrus cultivars. To date, at least sixteen bionematicides based on fungi and bacteria have been developed and marketed for use in citrus crops in various countries. Integration of bionematicides with other management tools as well as the conservation and enhancement of indigenous antagonists, will further enhance the management of citrus parasitic nematodes. Promising research avenues are discussed.

Antennal Transcriptome Analysis and Identification of Candidate Chemosensory Genes of the Harlequin Ladybird Beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae).

Simple SummaryThe predatory harlequin ladybird Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) has been widely released for classical and augmentative biological control programs of insect herbivores and is now distributed worldwide. Because of its invasive behavior and the threat it can pose to local biodiversity, this ladybird has been adopted as a model species for invasive biocontrol predators. A huge amount of existing literature is available on this species. However, little is known about the mechanisms underlying H. axyridis smell and taste, even though these senses are important in this ladybird for courtship, mating, and for locating suitable habitats for feeding and oviposition. Here we describe the first chemosensory gene repertoire that is expressed in the antennae of male and female H. axyridis. Our findings would likely represent the basis for future functional studies aiming at increasing the efficacy of H. axyridis in biological control or at reducing its populations in those areas where the ladybird has become a matter of concern due to its invasiveness.In predatory ladybirds (Coleoptera: Coccinellidae), antennae are important for chemosensory reception used during food and mate location, and for finding a suitable oviposition habitat. Based on NextSeq 550 Illumina sequencing, we assembled the antennal transcriptome of mated Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) males and females and described the first chemosensory gene repertoire expressed in this species. We annotated candidate chemosensory sequences encoding 26 odorant receptors (including the coreceptor, Orco), 17 gustatory receptors, 27 ionotropic receptors, 31 odorant-binding proteins, 12 chemosensory proteins, and 4 sensory neuron membrane proteins. Maximum-likelihood phylogenetic analyses allowed to assign candidate H. axyridis chemosensory genes to previously described groups in each of these families. Differential expression analysis between males and females revealed low variability between sexes, possibly reflecting the known absence of relevant sexual dimorphism in the structure of the antennae and in the distribution and abundance of the sensilla. However, we revealed significant differences in expression of three chemosensory genes, namely two male-biased odorant-binding proteins and one male-biased odorant receptor, suggesting their possible involvement in pheromone detection. Our data pave the way for improving the understanding of the molecular basis of chemosensory reception in Coccinellidae.

No deleterious effect of inundative releases of biological agents on native arthropod assemblages in poultry farms: A mesocosm experiment

Augmentative biological control relies on the inundative release of natural enemies of pests that are usually mass-reared in the laboratory. This practice substantially reduces the environmental impact of pest control in agriculture by reducing the use of insecticides. However, there are many reasons to expect more or less deleterious effects on biodiversity: if the enemy is not specific to the pest, the release of large populations of predators can directly affect native assemblages through the predation process itself and/or through competition with their native counterparts. In addition, mass-reared populations of enemies generally come from gene pools that are different from native populations and may, through the effects of hybridization, alter their population dynamics. On the other hand, during mass rearing, populations of natural enemies to be released are subject to different selection pressures from those in the field and may be less adapted than native populations to farm ecosystems. These effects are generally very difficult to assess in agro-ecosystems themselves due to the multiplicity of factors. In order to assess the effects of inundative releases of generalist predatory mites on native assemblages that colonize poultry houses from the surrounding environment, we conducted an experiment over several generations of mites using mesocosms mimicking a piece of a henhouse (mite-proof units, each housing one hen). No deleterious effects on native populations of Androlaelaps casalis and Cheyletus spp. have been detected from the mass introduction of marketed populations of A. casalis and C. eruditus. The mass introduction of marketed predatory mites against D. gallinae appears to be compatible with the conservation of native arthropod assemblages. The mass-reared populations of A. casalis and C. eruditus did not establish their populations under conditions which otherwise allowed their native counterparts (same taxa) to do so.

Examining potential intra-guild predation of Peristenus relictus by Geocoris punctipes, and its effects on the biological control of Lygus lineolaris

The generalist predator Geocoris punctipes (Say) and the parasitoid Peristenus relictus (Ruthe) are Lygus bug natural enemies. Augmentative biological control of some Lygus species has been attempted using either the predatory bug, or the parasitoid, but never in combination. In the present study, in laboratory assays, we determined whether G. punctipes engaged in intra-guild predation of P. relictus while developing in nymphs of Lygus lineolaris Palisot de Beauvois. In choice and no-choice experiments, G. punctipes preyed on more first and second instar nymphs of L. lineolaris than third and fourth instar nymphs. In choice and no-choice experiments G. punctipes ate more L. lineolaris nymphs that contained P. relictus eggs than nymphs containing P. relictus larvae; no nymphs containing P. relictus pupae were eaten. In experimental arenas in the laboratory, simultaneous release of G. punctipes and P. relictus achieved an additive effect on the mortality of L. lineolaris, killing 90, 80 and 70 percent of first, second and third instar nymphs, respectively. Although those are encouraging results for pest management, additional research on the interactions between these two natural enemies in commercial strawberry fields is needed before practical recommendations can be made.

Influence of the eggs of Ephestia kuehniella (Lepidoptera: Pyralidae) reared on different diets on the performance of the predatory bug Orius laevigatus (Hemiptera: Anthocoridae)

The predatory bug, Orius laevigatus (Fieber, 1860) (Hemiptera: Anthocoridae), is an important biological control agent and widely used for augmentative biological control of the western flower thrips, Frankliniella occidentalis Pergande, 1895 (Thysanoptera: Thripidae) in greenhouse crops. This bug is generally reared using the Mediterranean flour moth, Ephestia kuehniella Zeller, 1879 (Lepidoptera: Pyralidae). The aim of this study was to determine the effects of E. kuehniella eggs produced by adult moths reared on different larval diets on the performance of O. laevigatus. The diets were 95% cornmeal + 5% yeast (CY diet), 53.3% cornmeal + 26.7% wheat bran + 15% Glycerine + 5% yeast (CBGY diet) and 53.3% wheat flour + 26.7% wheat bran + 15% Glycerine + 5% yeast (WBGY diet). Laboratory studies started with newly emerged nymphs of O. laevigatus kept in a climate chamber at 27°C, 60% relative humidity and a 14L :10D photoperiod. Eggs of E. kuheniella adults that were fed on one of the three different larval diets were provided to the nymphs as a source of food and bean pods of water. Following adult emergence, all individuals were sexed, and female and male pairs were put in plastic containers (30 cc) with eggs of E. kuehniella and bean pods. Nymphal development time, fecundity and longevity of O. laevigatus were not differently affected by feeding on the eggs of E. kuehniella reared on the three diets. In addition, the daily and total egg consumption of adults of O. laevigatus were similar. Because the CY diet eggs contain more nutrients, their consumption by nymphs was lower. This study indicates that the CY diet is an adequate diet for rearing E. kuehniella for producing eggs for rearing O. laevigatus.

Feeding potential and foraging behaviour of Cheilomenes sexmaculata (F.) on the cotton aphid, Aphis gossypii glover

Feeding potential and foraging behaviour are two important factors which determine the predator’s efficiency of managing prey. Predator-prey system of Cheilomenes sexmaculata (Fabricius) and Aphis gossypii Glover was evaluated to find out the predation efficiency. Feeding potential was observed for different stages of C. sexmaculatus on A. gossypii whereas, functional and numerical responses were ascertained as a function of prey/host density. For the grub stage, highest feeding potential (101.43 ± 3.04 aphids) was observed for the fourth instar which was higher than the gross feeding potential of all other instars. Among the adults, female recorded high feeding potential with a mean daily consumption of 43.13 ± 0.54 aphids. Life table studies showed intrinsic rate of increase (r) of 0.22 with the mean generation time of 27.29 days. The foraging behaviour studies revealed that all the grub stages and adults displayed a type-II functional response. The IV instar grub has shown the lowest handling time with highest maximum predation (96.1aphids/day), followed by female (94.6), male (82.6) and other stages. However, female depicted a rapid extinction of aphid by keeping it below 25, as against fourth instar grub and male which affected extinction by keeping it below 30. So, the releases of fourth instar grub and female of C. sexmaculatus could be advocated for the augmentative biological control of A. gossypii.

Augmentative biological control in greenhouses in Japan

Abstract In Japan, augmentative biological control is mainly implemented in greenhouses using arthropod natural enemies. Two imported natural enemy species, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) against spider mites and Encarsia formosa Gahan (Hymenoptera: Aphelinidae) against the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), were first commercialised in greenhouses in 1995, followed by the commercialisation of other exotic species. Exotic arthropod natural enemies are used to control both exotic and indigenous pests in greenhouses. Currently, the most popular exotic natural enemy species are predatory mites such as P. persimilis and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Recently, there has been a shift from using exotic to using indigenous natural enemies in greenhouses. Currently, the importation of generalist predators for augmentative biological control is very difficult in Japan. Several collaborative studies have been conducted in Japan to develop biological control using indigenous natural enemies. These studies developed innovative technologies, such as new banker plant systems based on combinations of two natural enemies or flightless Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Indigenous natural enemies have been commercialised following the registration of Orius strigicollis (Poppius) (Hemiptera: Anthocoridae). Biological control can be achieved using an indigenous strain of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) with a banker plant system, on which the bug can reproduce without alternative prey. Research and development of biological control using indigenous natural enemies should be continued in Japan.

House Fly (Diptera: Muscidae): Biology, Pest Status, Current Management Prospects, and Research Needs

AbstractThe house fly, Musca domestica L. (Diptera: Muscidae), is a global pest of humans and animals that carries scores of pathogens and costs up to $1 billion per year in the United States alone. Information is reviewed on recognition, distribution, biology, dispersal, and associations with microbes. Particular challenges of managing flies in different animal systems are discussed for swine, poultry, dairy cattle, beef feedlot, and equine operations. Effective fly management requires diligent monitoring and integration of cultural control, especially manure management, with mechanical control, traps, conservation or augmentative biological control, and judicious use of insecticides. House fly is notorious for developing insecticide resistance and its resistance status is summarized as of August 2020. Several critical research needs are identified. Monitoring systems and nuisance/action thresholds need improvement. Faster-killing strains and better formulations are needed to integrate pathogens into Integrated Pest management (IPM) programs. The use of parasitoids remains an inexact science with many questions remaining about species selection and release rates. New attractants are needed for use in traps and attract-and-infect/kill strategies. Screening of new active ingredients for toxicity should continue, including a rigorous assessment of essential oils and other botanicals. Rising global temperatures may affect the balance of the fly with natural enemies. An understanding of the fly microbiome may reveal unknown vulnerabilities, and much remains to be learned about how flies acquire, retain, and transmit human and animal pathogens. System-specific research is also needed to tailor fly IPM programs to individual animal systems, especially in organic and free-range animal production.

Development and reproduction of Cataclysta lemnata, a potential natural enemy of the invasive alien duckweed Lemna minuta in Italy

Life cycle of the aquatic moth Cataclysta lemnata (Lepidoptera: Crambidae) was studied in laboratory conditions to obtain a basic biological knowledge useful for predicting the possible success of the herbivorous larvae of this insect as potential control agents in limiting the spread of the invasive American duckweed Lemna minuta (Alismatales: Araceae) in Italy. The multivoltinism of C. lemnata, as well as the high overall emergence from the pupal stage (85%), the high success in mating among the formed couples (>90%), and the high number of larvae born from each egg laying (on average 310 individuals), suggest that the insect can be successfully bred in the laboratory for the purposes of an augmentative biological control. Under experimental conditions, larvae developed in 23 days (through six larval instars, distinguishable by cephalic capsule dimensions) and pupae in 10, with no difference in duration between females and males. The larval phase resulted longer than the adult one (23 vs 10 days); therefore, it can be considered the most suitable stage for releasing the insect in the field for biocontrol purposes. Indeed, the larvae having a herbivorous diet might consume a large amount of the invasive plant, contrarily to the adult phase which is focused exclusively on reproduction. Our results not only contribute to the knowledge of aquatic Lepidoptera that are scarcely known, but also support the effectiveness of a possible protocol for an augmentative biological control of the invasive alien duckweed L. minuta.

Reclaimed desert habitats favor entomopathogenic nematode and microarthropod abundance compared to ancient farmlands in the Nile Basin

Abstract Characterizing entomopathogenic nematode (EPN) biogeography with a goal of augmentation and conservation biological control requires fine-scale taxonomic resolution, because closely related EPN species can exhibit divergent phenotypes for key properties such as habitat adaptation and insect host specificity. Consequently, we employed high throughput genome sequencing (HTS) to identify and compare EPNs and natural enemies of EPNs in 58 citrus orchards in 2 ecoregions in Egypt (El Beheira and Al Qalyubia governorates). We designed improved primers targeting the ITS2 rDNA to discriminate EPN species and used pre-reported primers targeting D2-D3 region for soil microarthropods. Five EPN species (Heterorhabditis bacteriophora, H. indica, H. taysearae, Steinernema glaseri, and S. scapterisci) and one steinernematid not represented in Genbank databases were detected. This is the first report of S. scapterisci and possibly the unknown (perhaps undescribed) species in Egypt. Only heterorhabditid species, dominated by H. indica, were detected in the reclaimed, sandy desert soils of El Beheira governorate. In the fine textured, ancient farming lands of the Nile delta all six species were detected, but at lower frequency and abundance. Microarthropod family richness (P = 0.01) and abundance (P = 0.001) was higher in the reclaimed lands than in the Nile Delta. Soil clay content, pH and elevation explained significant variation in the mite community structure. Population density of H. indica, the only EPN found consistently and at high abundance in El-Beheira, was inversely related to abundance of species in the nematophagous mite family Rhodacaridae.

Lack of phenotypic variation despite population structure in larval utilization of pea aphids by populations of the lady beetle Hippodamia convergens

The convergent lady beetle (Hippodamia convergens) is a generalist natural enemy that is utilized extensively in augmentative biological control across the United States. Recent studies have pointed to both genetic and phenotypic differences in Western (California) versus Eastern (Kansas) populations of the species. Here we investigate (1) genetic population structure, and (2) phenotypic differences in the utilization of pea aphids at temperatures that resemble the Western United States in (a) Eastern versus Western populations, (b) F1 Eastern X Western hybrids versus their progenitor populations, and investigate the effects of competition between (c) Eastern and Western populations. We found no differences in final pupal weight, or the net weight gain ratio through larval development from the third instar to pupal stage, despite genetic population structure. Our study points towards plastic response and effectiveness in feeding phenotypes of Eastern and Western populations of H. convergens, and the absence of hybrid vigor and heterozygote advantages in hybrids.

Functional response of Neochrysocharis formosa to Tuta absoluta

ABSTRACT Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive invasive pests of tomato worldwide. To improve biological control of T. absoluta, we studied the functional response of Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) to T. absoluta. Under laboratory conditions, N. formosa parasitised and host-fed on the first three larval instars, while the fourth instar was not selected for oviposition or feeding. The logistic regression analyses yielded significantly negative linear coefficients, confirming a type II functional response of the parasitoid to each host stage. Irrespective of the mode of host-killing, the attack rate was the highest and the handling time the lowest on the second instar host larvae. The theoretical maximum numbers of host larvae that a single mated female N. formosa could parasitise, host-feed or host-kill over a 24 h foraging period are 2.82, 2.87 and 5.66 (first instar); 3.50, 5.99 and 9.05 (second instar); and 2.28 1.71 and 3.38 (third instar), respectively. In conclusion, the parasitoid may enhance the augmentative and/or conservation biological control of T. absoluta under Indian conditions.

Exotic generalist arthropod biological control agents: need to improve environmental risk assessment to ensure safe use

Exotic generalist arthropod biological control agents (GABCAs) have been historically marginalized in classical and augmentative biological control due to their broad diet breadth, but an increasing demand for a more sustainable pest control is encouraging their reconsideration. This special issue compiles a collection of papers revealing that risks of several exotic GABCAs were overestimated, not all generalists are riskier than specialists and their environmental risk assessment (ERA) solely based on exposure analysis is inadequate. Three papers demonstrated that generalists were not involved in predicted non-target interactions: generalist idiobiont parasitoids probably do not exhibit interference competition with each other, an oligophagous exotic egg-larval koinobiont parasitoid does not compete with a native larval koinobiont, and an invasive generalist predator does not escape from its enemies. Two innovative methods for selecting non-target species are proposed, one based on existing food web data to predict indirect non-target effects, and the other on functional traits to predict competition with native natural enemies. Also a comprehensive GABCA-ERA method is proposed that integrates adverse effect analysis to the ‘conventional’ exposure analysis. The method was scrutinized by two studies: one suggesting that it could have resulted in faster and less costly decisions on two exotic generalists in New Zealand, and the other suggesting that eight exotic GABCAs released in Argentina might potentially reduce native natural enemies. We hope this special issue will stimulate the continued advance in the biosafety research of GABCAs so their safe use does not stagnate.

Influence of competition and predation on survival of the hydrilla tip mining midge and its success as a potential augmentative biological control agent of hydrilla

Hydrilla verticillata is an aquatic weed that grows densely throughout the water column and is costly to manage. The hydrilla tip mining midge, Cricotopus lebetis, a potential augmentative biological control agent of hydrilla, feeds on the apical meristem preventing growth. The goal of this study was to quantify the influence of a predator (mosquitofish, Gambusia sp.) and a competitor (hydrilla leafcutter moth, Parapoynx diminutalis) and their interactions, on the ability of the midge to survive and feed on hydrilla. The first experiment involved six treatments established in 37.8 L tanks with combinations of the organisms, including larval C. lebetis. Survival to adult midge eclosion was significantly reduced in the presence of the predator but was unaffected by the competitor’s presence alone. Apical meristem damage was reduced when both the competitor and predator were present. The second experiment included four treatments with C. lebetis egg masses or larvae and the presence or absence of mosquitofish. Adding C. lebetis as eggs rather than as larvae increased midge survival in the absence of the predator. Midge survival was lower when larvae were added, but the predator had no additional effect. To facilitate successful establishment of the midge and control of hydrilla, high numbers of larvae should be released to overcome predation.

Learned predators enhance biological control via organizational upward and trophic top-down cascades.

Learning is a behavioural change based on memory of previous experiences and a ubiquitous phenomenon in animals. Learning effects are commonly life‐stage‐ and age‐specific. In many animals, early life experiences lead to pervasive and persistent behavioural changes.There is broad consensus that learning has far‐reaching implications to biological control. Proximate and ultimate factors of individual learning by parasitoids and true predators are relatively well understood, yet the consequences of learning to higher organizational levels, populations and communities, and top‐down trophic cascades are unexplored.We addressed this issue using a tri‐trophic system consisting of predatory mites Amblyseius swirskii, Western flower thrips Frankliniella occidentalis and whole common bean plants, Phaseolus vulgaris. F. occidentalis are notorious horticultural pests that are difficult to control. Therefore, practitioners have much to gain by optimizing biological control of thrips.Previous studies have shown that early life experience of thrips by A. swirskii improves foraging on thrips later in life due to decreased prey recognition times and increased predation rates, together enhancing predator fecundity. Here, we hypothesized that early learning by A. swirskii enhances biological control of thrips via immediate and cascading effects. We predicted that release of thrips‐experienced predators enhances predator population growth and thrips suppression and reduces plant damage as compared to release of thrips‐naïve predators.The behavioural changes brought about by early learning cascaded up to the population and community levels. Thrips‐experienced predators caused favourable immediate and cascading effects that could not be compensated for in populations founded by thrips‐naïve predators. Populations founded by thrips‐experienced predators grew faster, reached higher abundances, were more efficacious in suppressing an emerging thrips population and kept plant damage at lower levels than populations founded by thrips‐naïve predators. Plant fecundity correlated negatively with thrips abundance and positively with predatory mite abundance. Improved biological control was mainly due to thrips‐experienced founders providing for a head‐start in predator population growth and thrips suppression. Synthesis and applications. Our study suggests that learned natural enemies have high potential to optimize augmentative biological control on a larger scale due to favourably modulating organizational upward and trophic top‐down cascades.