Biological Control Research Articles

Nonconsumptive effects of the predator Hippodamia convergens reduce probing behavior of Diaphorina citri on Citrus sinensis

AbstractNonconsumptive effects (NCEs) impact predator–prey interactions when the presence of a predator affects behavior, physiology, or population dynamics of the prey species without resulting in consumption. NCEs are critical to understanding ecological interactions broadly and in an applied manner, when addressing the efficacy of biological control within agroecosystems. In this study, we explore the impact of cues from the predator, Hippodamia convergens Guérin‐Méneville (Coleoptera: Coccinellidae), on the probing and feeding behavior of Diaphorina citri Kuwayama (Hemiptera: Psyllidae), the Asian citrus psyllid (ACP), which transmits the causal bacteria of Huanglongbing (HLB) disease of citrus (Rutaceae). Due to wide‐spread HLB incidence and insecticide resistance, it has become critical to better understand the activity of biological control agents within the HLB–ACP pathosystem. Utilizing electropenetrography (EPG), we investigated the feeding behavior of ACP exposed to the predator H. convergens or exposed to the chemical trails H. convergens produce while foraging. Overall, ACP detected H. convergens cues and responded by avoiding probing, although the extent of this response varied depending on the type of cue perceived. When H. convergens was present in the leaf but unable to reach the psyllid, ACP were slower to initiate probing and spent less time overall on probing and feeding from the xylem. In contrast, when exposed to H. convergens foraging cues without the beetle present, ACP initiated probing quicker than when the beetle was present and had a shorter total probing time compared to the control, with no other parameters being affected. Interestingly, the H. convergens chemical trail extracts, at two dosages, did not significantly influence ACP probing and feeding, except for a lower proportion of salivation and ingestion events into the phloem at the lower test dose. Our results suggest ACP exhibits avoidance behaviors in response to H. convergens cues, leading to a reduction in feeding, which suggests the maintenance of agroecosystem health through preservation of insect community diversity may be overlooked as an additive factor in vector management.

Reproductive and biological control performance of in vitro and in vivo reared Trichogramma dendrolimi on Spodoptera frugiperda

Reproductive and biological control performance of in vitro and in vivo reared Trichogramma dendrolimi on Spodoptera frugiperda

Pathogenicity of Serratia marcescens strains as biological control agent: Implications for sustainable pest management.

The escalating demand for sustainable and eco-friendly pest management strategies has raised interest in harnessing the pathogenic potential of microorganisms. Serratia marcescens, a Gram-negative bacterium, has emerged as a potential biological control agent for sustainable pest management. This review critically examines the history, biology, identification, and pathogenicity of S. marcescens strain with their potential application in pest management. The diverse mechanisms employed by the strain to exert control over pests, including the production of metabolites and the induction of systemic resistance in plants, are examined. The review also summarizes the ecological significance and global distribution of S. marcescens associated with the use of S. marcescens in biological control strategies. Furthermore, the usage efficacy of S. marcescens over other conventional chemicals is discussed. A comprehensive understanding of the pathogenic potential of S. marcescens strains as biological control agents is crucial for developing effective and sustainable pest management strategies. This review consolidates current research advances on S. marcescens, and provides insights into the prospects and challenges of using S. marcescens for integrated pest management.

Legacies of a Large Flood and Biological Control on Riparian Vegetation Successional Trajectories Along a Dryland Braided River

ABSTRACTThe interplay of disturbance and stability drives vegetation dynamics. Disturbance reduces vegetation biomass, and stability fosters its development. In riparian systems, natural disturbance is largely manifested through flood‐driven fluvial processes, but other forms of disturbance, such as herbivory or fire, may influence vegetation dynamics. We studied the successional trajectories of plant communities following a 40‐year flood in 2010 that significantly changed floodplain vegetation along the lower Virgin River (southwestern USA). Shortly (0–2 years) after this flood, another large disturbance event of a different nature occurred: extensive defoliation and some mortality of alien Tamarix shrubs (which dominated vegetation cover at that time in the study area) by a biological control beetle. In 2021, we resampled vegetation and topography in 439 plots that we previously monitored in 2010, 2012, 2015, and 2017 along 23 transects across five river reaches. Between 2015 and 2021, stability predominated, with only small floods (1.5‐ to 3‐year) and limited Tamarix defoliation. By 2021, plant communities were converging, but persistent divergences existed and were associated with legacy effects of fluvial disturbance and defoliation. Native Pluchea sericea shrubs had the highest cover across all fluvial landforms. Tamarix partially recovered from defoliation, but only reached similar cover to P. sericea in plots less affected by the 40‐year flood. Native Populus fremontii, Prosopis pubescens, and Salix gooddingii trees, and Salix exigua shrubs, remained subordinate. Our study illustrates how successional trajectories in riparian systems depend on the nature and regime of disturbance and its legacy effects on vegetation.

First report of Trichopoda pictipennis (Diptera, Tachinidae) for the Canary Islands

The genus Trichopoda Berthold, 1827 is distributed in the Neotropical and Nearctic Regions and some species are very important for biological control. During the last decades, the species Trichopoda pictipennis Bigot, 1876 has received much attention. It is of Neotropical origin, but it has been introduced throughout the western Palaearctic, probably through exchanges that transported its main host, the 'southern green stink bug' Nezara viridula. Trichopoda pictipennis is reported for the first time from the Canary Islands. To date, this introduced species has been detected throughout the island of Tenerife and in a single locality on the island of La Gomera. This finding confirms that this species of Neotropical origin is expanding its range across the Palaearctic realm of this species of Neotropical origin. Parasitised Nezara viridula were collected and reared under laboratory conditions to document the complete life cycle of T. pictipennis. Its potential effects on its main host, as well as on the Canary fauna, are discussed.

Septoria lamiicola Causing Leaf Spot on Lamium purpureum in Korea.

Lamium purpureum L. (purple dead-nettle), an annual herbaceous plant in the family Lamiaceae, is native to Europe and western Asia. It has become invasive in eastern Asia, including Korea and North America. Due to its rapid growth and tolerance of disturbed soils, it invades croplands and natural ecosystems, reducing crop yields (Mock et al. 2009). It also serves as an overwintering host for cucumber mosaic virus (Tomlinson et al. 1970). Leaf spots on purple dead-nettle were first observed in April 2022 in Gimje (35°43'10"N, 127°00'42"E) and in April 2023 in Jangsu (35°36'16"N, 127°22'43"E), Korea, with a disease incidence of 20-30% among surveyed plants. Symptoms were distinct, angular, pale brown to brown, and bordered by leaf veins. Numerous blackish conidiomata with cirriform conidial horns were visible on the spots. Conidiomata were numerous, scattered, pycnidial, amphigenous but abundantly epigenous, scattered, dark brown to rusty brown, globose, embedded in host tissue or partly erumpent, 60 to 110 µm in diameter, with ostioles measuring 28 to 56 µm in diameter. Conidiogenous cells lining the inner wall layer were hyaline and ampulliform. Conidia were filiform, straight or slightly curved, 32 to 48 × 2 to 3 µm, hyaline, 2 to 5-septate, but often 3-septate. Morphological descriptions were consistent with Septoria lamiicola Sacc. (Verkley et al. 2013). For monoconidial isolation, a conidial horn was collected, placed in a 1.5 ml tube containing sterile water, and streaked onto the surface of 2% water agar (WA). After four days, a hyphal tip was transferred to fresh potato dextrose agar (PDA). Colonies incubated for two weeks at 25°C on PDA were measured 10 to 15 mm in diameter, with a white to greyish at the center and a dark grey to black at the margin. Voucher specimens were deposited at the Korea University Herbarium (KUS-F32758 and F33612), and a representative culture was deposited at the Korea Agricultural Culture Collection (Acc. No. KACC 410468). Nucleotide sequences of the internal transcribed spacer (ITS), 28S rDNA (LSU), β-tubulin (TUB2), translation elongation factor 1-α (EF), actin (ACT), and RNA polymerase II second largest subunit (RPB2) genes were determined (Verkley et al. 2013) and deposited in GenBank (Accession Nos: PQ061283, PQ106849, PQ120989, PQ120981, PQ120994, and PQ120985). BLASTn search of the sequences showed 100% identity with the reference sequences of Septoria lamiicola CBS 102328 for ITS (KF251441.1), LSU (KF251945.1), ACT (KF253745.1), and RPB2 (KF252438.1). The TUB2 sequences showed 99.7% similarity (1/311 nucleotides different) with KF252913.1, and the EF sequences showed 96.0% similarity (13/368 different) with KF253389.1. In a phylogenetic tree reconstructed using the multi-loci sequences, the Korean isolate formed a well-supported group with reference isolates of S. lamiicola (Verkley et al. 2013). Pathogenicity was tested twice by spraying a conidial suspension (1×104 conidia/mL) harvested from a four-week-old culture (KACC 410468) onto twenty leaves of three-potted plants (two months old). Three control plants were sprayed with sterile distilled water. Plants were placed in a dew chamber at 26°C for 24 h before being transferred to a greenhouse. After ten days, typical symptoms appeared on the inoculated leaves, while no symptoms were observed on the controls. S. lamiicola was re-isolated from the symptomatic lesion and confirmed by microscopy, fulfilling Koch's postulates. Although S. lamiicola has been recorded on L. purpureum in Bulgaria, Poland, and Portugal (Farr and Rossman 2024), there is no previous record of this fungus in Korea. To our knowledge, this is the first report of leaf spot caused by S. lamiicola on L. purpureum in Korea. Septoria lamiicola could be utilized as a biological control agent against this invasive weed, thereby supporting sustainable management strategies for croplands and natural ecosystems.

New Records of Phenacoccus solenopsis Natural Enemies in Europe and Taxonomic Additions on Anagyrus matritensis

The cotton mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae) is a polyphagous invasive species native to America and considered one of the major cotton pests in Asia. It is currently threatening horticultural and ornamental protected crops in Mediterranean countries. Due to ecological and environmental concerns, the conventional chemical control of P. solenopsis in new areas of introduction is being replaced by exploring the potential of indigenous natural enemies as a sustainable biological control tool. After P. solenopsis introduction in Sicily (Italy), field surveys were conducted on native natural enemies attacking the mealybug to select promising biocontrol agents for field applications. For the first time, Aenasius arizonensis (Hymenoptera: Encyrtidae) was reported in Europe, and the native Anagyrus matritensis (Hymenoptera: Encyrtidae) was recorded in association with P. solenopsis. The two parasitoid species were identified by morphological features and molecularly using a portion of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene. Because of missing information, additional morphological features were provided for the morphological identification of A. matritensis. In addition, the generalist predators Cryptolaemus montrouzieri, Hippodamia variegata and Parexochomus nigripennis (Coleoptera: Coccinellidae) were also recorded attacking the invasive mealybug.

A comprehensive review of mycoviruses infecting the plant pathogenic fungus Rosellinia necatrix

The number of documented viruses that infect fungi has increased during the past few decades. Mycoviruses that infect plant pathogenic fungi are the main focus of mycoviral research since some of them have the capacity to cause hypovirulence to their host and hence function as potential biocontrol agents. This article provides a comprehensive overview of mycoviruses infecting plant pathogenic fungus Rosellinia necatrix causing white root rot, including the prevalence of their occurrence, their taxonomic classification, their genomic organization and structure, impacts on their fungal host in terms of phenotype in general and virulence in particular, and their ecological interactions including transmission. The white root rot fungus is found to harbor diverse mycoviruses with double-stranded and positive-sense single-stranded RNA genomes from different families, including Spinareoviridae, Megabirnaviridae, Partitiviridae, Quadriviridae, Pseudototiviridae, Endornaviridae, Fusariviridae, Yadokariviridae, Hypoviridae, Fusagraviridae and Megatotiviridae. Some of these mycoviruses studied in R. necatrix or a heterologous host Cryphonectria parasitica revealed interesting virus-host interplays and appear to be promising agents for biological control applications against white root rot.

Quality traits of the lady beetle Eriopis connexa (Germar) resistant to pyrethroids over 130 generations of rearing

Abstract Augmentative biological control requires the rearing of large quantities of natural enemies to meet customers' demands. We hypothesise that successive generations of an insecticide‐resistant lady beetle population, under constant physical conditions and fed alternative prey, could compromise its quality as a natural enemy. Adaptive costs of resistance are particularly high in insecticide‐resistant populations. The predatory lady beetle, Eriopis connexa (Germar), exhibits resistance to λ‐cyhalothrin (EcViR), and others pyrethroids. We compared the biological and predatory traits of the EcViR population to those of a field‐collected and susceptible population (EcCV). During 35 days of observations, when females from both populations faced food shortages, EcViR females demonstrated higher fecundity and similar survival rates. Predation of the aphid, Lipaphis pseudobrassicae (Davis), resulted in a similar response for both populations and greater aphid consumption by EcViR beetles in the presence of λ‐cyhalothrin residue. Rearing larvae and adults at three constant temperatures (18, 25, and 32°C) resulted in similar developmental times between populations, but adult EcCV beetles were larger and produced more eggs at 25 and 32°C. The results show that food shortages did not affect the reproductive output or the developmental time at 18, 25, and 32°C in EcViR compared with EcCV. Nevertheless, egg production at 25 and 32°C was lower for EcViR females than for EcCV. Among the studied traits, only an effect on fecundity was observed, as predicted previously, due to the adaptive cost of resistance in EcViR, which became more evident at higher temperatures.

Application of omics technology in ecotoxicology of arthropod in farmland

Abstract Arthropods, abundant in farmland, have unique biological traits that make them valuable for studying the ecotoxicological impacts of pollutants. Recent advancements in multi-omics technologies have enhanced their use in assessing pollution risks and understanding toxicity mechanisms. This paper reviews recent developments in applying omics technologies—genomics, transcriptomics, proteomics, metabolomics and meta-omics to ecotoxicological research on farmland arthropods. Agricultural arthropods manage genes and proteins like metallothioneins (MTs), antioxidant enzyme systems, heat shock proteins, cytochrome P450 (CYP450), carboxylesterases (CarEs), and glutathione S-transferases (GSTs), for detoxification and antioxidant purposes. They adjust amino acid, sugar, and lipid metabolism to counteract pollutant-induced energy drain and modify gut microbiota to aid in detoxification. This study advocates for enhanced analysis of compound pollution and emerging pollutants using multi-omics, especially meta-omics, to clarify the toxicological mechanisms underlying arthropod responses to these pollutants. Furthermore, it underscores the urgent need for subsequent gene function mining and validation to support biological control strategies and promote sustainable agricultural practices. The findings of this research provide significant insights into the toxicological impacts and mechanisms of pollutants within farmland ecosystems, thereby contributing to the preservation of arthropod diversity.

Bacillus velezensis CE 100 controls anthracnose disease in walnut trees (Juglans regia L.) by inhibiting Colletotrichum gloeosporioides and eliciting induced systemic resistance.

Biological control of plant diseases is recognized as an effective and environmental friendly alternative to chemical fungicides. We demonstrated the dual biocontrol strategy of Bacillus velezensis CE 100 through the hydrolytic activity of chitinase and β-1,3-glucanase and the elicitation of induced systemic resistance (ISR) against Colletotrichum gloeosporioides that causes anthracnose disease in walnut trees. B. velezensis CE 100 produced a maximum of 62.1 units mL-1 (132.9 units mL-1) chitinase and 5.2 units mL-1 (9.4 units mL-1) β-1,3-glucanase enzymes in the broth culture (crude enzyme fraction), and inhibited spore germination and mycelial growth of C. gloeosporioides by 81.6% and 22.6%, respectively, at 100µlmL-1 of crude enzyme fraction. The inoculation of B. velezensis CE 100 induced the production of pathogenesis-related (PR) chitinase in walnuts by 2.1-fold, and to a lesser extent PR β-1,3-glucanase, and reduced anthracnose disease severity by 3.0-fold compared to the control group. The bacterium produced a maximum of 11.4µgmL-1 indole-3-acetic acid (IAA) and improved the chlorophyll content, shoot length, and root collar diameter of walnut trees compared to the fungicide treatment and control groups. B. velezensis CE 100 demonstrated the prospect of controlling walnut anthracnose by direct antagonism and ISR against C. gloeosporioides, while simultaneously enhancing walnut growth through IAA production.

Exploring climate-driven phenological mismatches in pears, pests and natural enemies: a multi-model approach

Abstract Pear psyllid (Cacopsylla pyri) is the dominant pest of UK pear orchards, with an estimated cost of £5 million per annum. Insecticide withdrawal and increased pesticide resistance of C. pyri have led many growers to depend more on natural enemies for pest management, including earwigs. However, there is concern how phenological events may shift with future climate change, which may result in phenological mismatches. This study aimed to determine shifts in timing of phenological events within an agroecosystem and predict phenological mismatches or synchronies between trophic levels. We evaluated three models: the C. pyri phenology model, the earwig degree day model and the PhenoFlex model (flowering time). Phenological events predicted by models included: first, full and last flowering time for Pyrus communis; peak psyllid abundance date for first-generation (G1) C. pyri nymphs and second-generation (G2) eggs, nymphs and adults; and peak abundance date for stage 4 Forficula auricularia and adults. Findings indicated that the timing of phenological events was advancing for all trophic levels, becoming significantly earlier under the current time period. Furthermore, predictions indicated that timing events would continue to advance under the RCP8.5 scenario. However, not all phenological events advanced at the same rate; the date of peak C. pyri G1 nymph abundance advanced at a higher rate than full flowering time, which could result in a phenological mismatch by 2071. Conversely, C. pyri and F. auricularia showed phenological synchrony, with peak abundance dates advancing at a similar rate, which could be beneficial for future biological control.

Pantoea–Bacillus as a Composite Microbial Community: Inhibition and Potential Mechanism Against Potato Anthracnose Disease

The potato (Solanum tuberosum), an important component of global food security, often faces threats from various diseases during its growth process, especially potato anthracnose (Colletotrichum coccodes), which severely affects crop yield and quality. In this study, we successfully isolated and identified two bacteria with potential for biological control, (Pantoea agglomerans) and (Bacillus subtilis).The experimental results indicate that the bacterial suspensions of strains JZ-1-1-1 and JZ-2-2-2 had a significant inhibitory effect on the pathogen ZL-7, with the inhibition rate of JZ-1-1-1 reaching as high as 55.21%. The inhibition rate of JZ-2-2-2 was 53.48%. When these two strains were mixed at a 4:6 ratio, the inhibitory effect on pathogenic bacteria was even more significant, reaching 68.58% inhibition. In addition, the composite microbial community produced biofilms with their yield gradually increasing within 24 h and showing a slight decrease after 72 h. The efficacy test further indicated that the composite bacterial suspension was highly effective in controlling the spread of lesions, with an efficacy rate as high as 81.40%. In the analysis of defense enzyme activity, peroxidase (POD) and superoxide dismutase (SOD) levels peaked on day seven, while the composite bacterial suspension significantly reduced malondialdehyde (MDA) and polyphenol oxidase (PPO) activity. Quantitative real-time PCR confirmed that these two strains effectively colonized the surface of potato tubers. In summary, this study provides an important theoretical basis and practical guidance for the application of biological methods for the prevention and control of potato anthracnose.

PxDorsal Regulates the Expression of Antimicrobial Peptides and Affects the Bt Susceptibility of Plutella xylostella

The insect NF-κB pathway is primarily constituted by nuclear factor κB (NF-κB) and the inhibitor of κB (IκB), which plays a crucial role in the innate immune response. Dorsal and Cactus, as NF-κB and IκB factors, are important downstream regulators of the Toll pathway in Plutella xylostella. In this study, the PxDorsal and PxCactus genes of P. xylostella were cloned, and the molecular docking demonstrated that PxDorsal and PxCactus can interact with each other. RT-qPCR results indicated that PxDorsal and PxCactus were expressed in all stages, and the expression of PxDorsal, PxCactus, and antimicrobial peptides PxGloverin2, PxMoricin3, and PxLysozyme2 were significantly down-regulated under Bacillus thuringiensis (Bt8010) infection. Interestingly, silencing the PxDorsal gene by RNA interference (RNAi) significantly down-regulated the expression of PxGloverin2 and PxMoricin3 and increased the epidermis melanization of P. xylostella larvae fed with Bt8010. Our findings indicate that PxDorsal and PxCactus may interact with each other, and silencing PxDorsal inhibits the expression of downstream antimicrobial peptides, thereby enhance the susceptibility of P. xylostella to Bt8010. This study contributes a theoretical basis for further research on the Toll pathway of P. xylostella to pathogens and offers insights for screening effective biological control targets from the perspective of the immune system.

The utilization of biological control against regulated pests in the EPPO region: challenges and opportunities

AbstractBiological control is a pest control method that can offer an environmentally safer alternative to chemical pesticides. The proven safety record of both augmentative and classical biological control technologies allows its utilization against indigenous and non‐indigenous but well‐established pests, whether under protected conditions (e.g., glasshouses) or in open field cropping systems. This manuscript has been developed by the Joint European and Mediterranean Plant Protection Organization (EPPO) and the International Organization for Biological and Integrated Control (IOBC) Panel on Biological Control Agents and presents an assessment on the current use of classical and augmentative biological control for the control of regulated plant pests. The paper discusses challenges for the uptake of biological control for regulated pests and provides recommendations to increase the safe use of biological control agents in the EPPO region.

Orchard systems offer low-hanging fruit for low-carbon, biodiversity-friendly farming

Abstract As core constituents of healthy diets, fruits are often cultivated in temporally stable and structurally complex ecosystems that harbor high levels of biodiversity. However, high-intensity orchard management can lessen the human and environmental health benefits of fruticulture. In the present article, we argue that increased emphasis on biological control could contribute to preventative management of fruit pests, weeds, and diseases, resulting in pesticide phasedown. Carefully calibrated orchard management can increase the provision of ecosystem services by above- and belowground biota, improve soil health, and store atmospheric carbon. When tactically integrated with agroecological measures, behavior-modifying chemicals, or digital tools, biological control helps to conserve pollinator or soil fauna, protect vertebrate communities, and improve vegetation restoration outcomes. Its implementation can, however, give rise to scientific and social challenges that will need to be explored. By resolving the adoption hurdles for biological control at scale, human society could enjoy the myriad benefits of nature-friendly fruit production.

Commercial availability of invertebrate biological control agents targeting plant pests in Germany

Abstract Biological control is a recognized and well-implemented strategy to protect crops from pests and diseases, and there is an urgent need to expand biocontrol-based crop protection further, also in Germany. Specially, the use of invertebrate biological control agents (IBCA) is considered as a fundamental method in integrated pest management and organic farming. The objective of this article is to give an overview of the current commercially available and used IBCA species in Germany. Of those, individual non-indigenous species are critically examined for potential environmental risks. Furthermore, the current legal situation in Germany about the use of IBCA is described. Based on this information, this article clarifies the need for an environmental impact assessment for IBCA species that do not occur naturally in Germany. An outlook for their safe use in the future is discussed.

Non-target effects of insecticides and herbicides on earwigs.

Conservation biological control in agriculture primarily relies on avoiding pesticides that may harm key natural enemies. In temperate tree fruit crops, the European earwig, Forficula auricularia (L.) has only recently become appreciated as an important predator of economic pests, particularly woolly aphids and pear psylla. Therefore, the non-target effects of orchard pesticides on earwigs are largely understudied. This is particularly true for herbicides, which earwigs are likely to be exposed to due to their foraging behavior moving between the canopy and the ground cover. We tested residues of formulated pesticides (8 insecticides and 7 herbicides) commonly used in tree fruit crops for lethal and sublethal (movement, predation rate) effects on adult female earwigs. Two herbicides, paraquat and glufosinate, and one insecticide, spinetoram, were acutely toxic to earwigs within 72h. No tested pesticides altered earwigs' movement or resting behavior compared to the control. The insecticides spinosad and cyantraniliprole and the herbicides 2,4-D, glufosinate, halosulfuron, rimsulfuron, and oxyfluorfen reduced earwig predation on green peach aphids. Therefore, these pesticides may reduce earwig predation on pests in orchards. Our results suggest that some pesticides are of greater risk, and thus, should be carefully considered or better timed when used in tree fruit orchards where earwigs are considered for conservation or augmentative biological control.

Field trial of biologicals for managing potato early dying complex in Maine, 2024

Potato early dying complex is caused by fungal pathogen Verticillium dahliae and Pratylenchus root lesion nematodes. It is an economically impactful potato disease in the United States. Symptoms include decreased tuber yield, unilateral wilting, chlorosis, and necrosis of leaves, and brown vascular discoloration in stems and tubers. This report evaluates the efficacy of two biological controls in conjunction with a traditional chemical management of potato early dying complex. This trial was conducted in Presque Isle, ME in 2024 on potato (Solanum tuberosum) ‘Kennebec’. Results from this study can help advise potato producers in the U.S. in managing this disease complex.

Three‐trophic level food webs support the safety of a biocontrol agent 3 years after release

Biological control (biocontrol) is a powerful tool for managing invasive alien species and assisting the restoration of native ecosystems. Rigorous post‐release monitoring of biocontrol agents is critical to evaluate the success of biocontrol programs; however, this is still rarely implemented. Here, we combined the use of species interaction networks with a Before‐After Control‐Impact design to evaluate the target and non‐target, direct and indirect effects of the Australian gall wasp Trichilogaster acaciaelongifoliae, released to control the invasive plant Acacia longifolia in Portugal. We compared the structure of plant‐galling insect‐parasitoid food webs before and 3 years after the release of the biocontrol agent. Exhaustive sampling did not detect any non‐target effects, either direct (on non‐target plants) or indirect (on other galling insects via shared plants). Additionally, no significant changes were detected in network structure that could be related to the establishment of the biocontrol agent. This study shows that monitoring biocontrol at the community level is possible and that, when carefully planned, biocontrol poses minimal risk of non‐target effects.