Biocontrol Systems Research Articles

Expanding the transgene expression toolbox of the malaria vector Anopheles stephensi.

Anopheles stephensi Liston, 1901 (Diptera: culicidae) is a competent vector of Plasmodium falciparum (Haemosporida: plasmodiidae) malaria, and its expansion in the African continent is of concern due to its viability in urban settings and resistance to insecticides. To enhance its genetic tractability, we determined the utility of a ~2 kb An. stephensi lipophorin (lp) promoter fragment in driving transgene expression. Lipophorin genes are involved in lipid transport in insects, and an orthologous promoter in An. gambiae (AGAP001826) was previously demonstrated to successfully express a transgene. In the present study, we qualitatively characterised the expression of a ZsYellow fluorescent marker protein, expressed by An. stephensi lp promoter fragment. Our study indicated that the lp promoter fragment was effective, generating a distinct expression pattern in comparison to the commonly utilised 3xP3 promoter. The lp:ZsYellow fluorescence was largely visible in early instar larvae and appeared more intense in later instar larvae, pupae and adults, becoming especially conspicuous in adult females after a blood meal. Different isolines showed some variation in expression pattern and intensity. Aside from general transgene expression, as the lp promoter produces a suitable fluorescent protein marker expression pattern, it may facilitate genotypic screening and aid the development of more complex genetic biocontrol systems, such as multi-component gene drives. This study represents an expansion of the An. stephensi genetic toolbox, an important endeavour to increase the speed of An. stephensi research and reach public health milestones in combating malaria.

Application of a Standardized Impact Monitoring Protocol (SIMP) to assess biological weed control projects in the State of Idaho, USA

In the USA, the lack of systematic post-release assessments of weed biological control projects demonstrating quantitative effects of biological control agents on target weed densities, population biology, and/or vegetation responses remain a concern. While there are numerous quantitative assessments, overall conclusions are limited in scope by the spatial scale covered, duration of study, potentially confounding factors, or weed parameters measured. The United States Department of Agriculture’s Animal Plant Health Inspection Service is the regulatory agency responsible for biological control agent releases. USDA APHIS requires post-release impact monitoring of target weed populations as part of release permits issued for new biological control agents. However, large scale, long-term impact assessments are rarely conducted for a variety of reasons. To address this problem, biocontrol practitioners developed a standardized impact monitoring protocol (SIMP) for the State of Idaho in 2007. The intent was to collect ecological data which are sufficiently robust for quantitative analysis, while minimizing time spent in the field to make data collection appealing to citizen scientists and land managers. SIMP has since been implemented for ten weed biocontrol systems, with more than fifteen years of monitoring data for some systems. SIMP data are collected along permanent transects and include weed density and size parameters, categorical vegetation community and biocontrol agent abundance data. Data are repeated measures, which are well suited for dynamic population modeling and can be coupled with environmental factors (e.g., climate or soil data) to analyze how processes like climate (and climate change) can drive variation in weed biocontrol agent interactions. SIMP data can be combined with detailed weed, nontarget plant and/or biocontrol agent surveys to add analytical data. Finally, SIMP has also been implemented for two weeds for which biological control agents have not yet been introduced to provide weed and community vegetation data prior to releases.

Electromyography signal based hand gesture classification system using Hilbert Huang transform and deep neural networks

This research aims to provide the groundwork for smartly categorizing hand movements for use with prosthetic hands. The hand motions are classified using surface electromyography (sEMG) data. In reaction to a predetermined sequence of fibre activation, every single one of our muscles contracts. They could be useful in developing control protocols for bio-control systems, such human-computer interaction and upper limb prostheses. When focusing on hand gestures, data gloves and vision-based approaches are often used. The data glove technique requires tedious and unnatural user engagement, whereas the vision-based solution requires significantly more expensive sensors. This research offered a Deep Neural Network (DNN) automated hand gesticulation recognition system based on electromyography to circumvent these restrictions. This work primarily aims to augment the concert of the hand gesture recognition system via the use of an artificial classifier. To advance the recognition system's classification accuracy, this study explains how to build models of neural networks and how to use signal processing methods. By locating the Hilbert Huang Transform (HHT), one may get the essential properties of the signal. When training a DNN classifier, these characteristics are sent into it. The investigational results reveal that the suggested technique accomplishes a better categorization rate (98.5 % vs. the alternatives).

Aflatoxins in the nut chains: strategies to reduce their impact on consumer’s health and economic losses

Abstract The presence of Aspergillus section Flavi and aflatoxins (AFs) in nut chains are of great concern due to the toxic effects of AFs on human and animal health as well as the economic losses during commercialisation. Extreme events related to climate change like increased temperature, severe rainfalls and droughts are modulating factors of fungal growth and mycotoxin production. The Expert Working Group (EWG) on nuts that worked under the frame of the Horizon 2020 Mycokey Project prepared this review based on discussions about the situation of contamination with AFs in nuts and the available strategies to reduce the impact of these toxins in the nut chains. The EWG selected as examples peanuts, pistachios and Brazil nuts, and discussed in the review the importance of nut value chains in the production, commercialisation and regulations that establish maximum levels for AFs. Also data on the Rapid Alert System for Food and Feed (RASFF) was considered and showed several notifications for mycotoxins, mainly AFs for nuts and nut products, such as pistachio nuts and dried mix nuts. Under a scenario of climate change, we elaborated strategies to prevent AFs contamination with emphasis on biocontrol and decision support systems. Also, the relevance of strategies to prevent and reduce both fungal infection and AFs accumulation in peanuts, Brazil nuts and pistachio are included as guidelines.

Changes in longevity, parasitization rate and development time of the whitefly parasitoid Encarsia formosa under future climate conditions

Biological control by augmentative release of parasitoids is an established practice for controlling an economically very important insect pest group, whiteflies (Aleyrodidae), in protected cropping systems worldwide. One of the two most used parasitoids is Encarsia formosa. Anthropogenic climate change will modify multitrophic interactions between organisms, and sensitive biocontrol systems are not an exception. At the same time, there is a knowledge gap in our understanding of the performance of E. formosa as a biocontrol agent in mid-future climate. In the present study, we evaluate the parasitization rate, development time, and longevity of this important biocontrol agent by performing climatic chamber simulation driven by physically consistent, regionally downscaled, numerical future climate projections. The parasitoid shows 8.6 days accelerated development, 15-fold higher parasitization rate, and 38% shorter longevity under the tested future climate conditions. Challenges in conclusively assessing life parameters of this parasitoid, and the implications on whitefly biocontrol in the future are discussed.

Exploring yeast-based microbial interactions: The next frontier in postharvest biocontrol.

Fresh fruits and vegetables are susceptible to a large variety of spoilage agents before and after harvest. Among these, fungi are mostly responsible for the microbiological deteriorations that lead to economically significant losses of fresh produce. Today, synthetic fungicides represent the first approach for controlling postharvest spoilage in fruits and vegetables worldwide. However, the emergence of fungicide-resistant pathogen biotypes and the increasing awareness of consumers towardthe health implications of hazardous chemicals imposed an urgent need to reduce the use of synthetic fungicides in the food supply; this phenomenon strengthened the search for alternative biocontrol strategies that are more effective, safer, nontoxic, low-residue, environment friendly, and cost-effective. In the last decade, biocontrol with antagonistic yeasts became a promising strategy to reduce chemical compounds during fruit and vegetable postharvest, and several yeast-based biocontrol products have been commercialized. Biocontrol is a multipartite system that includes different microbial groups (spoilage mold, yeast, bacteria, and nonspoilage resident microorganisms), host fruit, vegetables, or plants, and the environment. The majority of biocontrol studies focused on yeast-mold mechanisms, with little consideration for yeast-bacteria and yeast-yeast interactions. The current review focused mainly on the unexplored yeast-based interactions and the mechanisms of actions in biocontrol systems as well as on the importance and advantages of using yeasts as biocontrol agents, improving antagonist efficiency, the commercialization process and associated challenges, and future perspectives.

Chromosome-level genome assemblies of two parasitoid biocontrol wasps reveal the parthenogenesis mechanism and an associated novel virus

BackgroundBiocontrol is a key technology for the control of pest species. Microctonus parasitoid wasps (Hymenoptera: Braconidae) have been released in Aotearoa New Zealand as biocontrol agents, targeting three different pest weevil species. Despite their value as biocontrol agents, no genome assemblies are currently available for these Microctonus wasps, limiting investigations into key biological differences between the different species and strains.Methods and findingsHere we present high-quality genomes for Microctonus hyperodae and Microctonus aethiopoides, assembled with short read sequencing and Hi-C scaffolding. These assemblies have total lengths of 106.7 Mb for M. hyperodae and 129.2 Mb for M. aethiopoides, with scaffold N50 values of 9 Mb and 23 Mb respectively. With these assemblies we investigated differences in reproductive mechanisms, and association with viruses between Microctonus wasps. Meiosis-specific genes are conserved in asexual Microctonus, with in-situ hybridisation validating expression of one of these genes in the ovaries of asexual Microctonus aethiopoides. This implies asexual reproduction in these Microctonus wasps involves meiosis, with the potential for sexual reproduction maintained. Investigation of viral gene content revealed candidate genes that may be involved in virus-like particle production in M. aethiopoides, as well as a novel virus infecting M. hyperodae, for which a complete genome was assembled.Conclusion and significanceThese are the first published genomes for Microctonus wasps which have been deployed as biocontrol agents, in Aotearoa New Zealand. These assemblies will be valuable resources for continued investigation and monitoring of these biocontrol systems. Understanding the biology underpinning Microctonus biocontrol is crucial if we are to maintain its efficacy, or in the case of M. hyperodae to understand what may have influenced the significant decline of biocontrol efficacy. The potential for sexual reproduction in asexual Microctonus is significant given that empirical modelling suggests this asexual reproduction is likely to have contributed to biocontrol decline. Furthermore the identification of a novel virus in M. hyperodae highlights a previously unknown aspect of this biocontrol system, which may contribute to premature mortality of the host pest. These findings have potential to be exploited in future in attempt to increase the effectiveness of M. hyperodae biocontrol.

Longevity of the whitefly parasitoid Eretmocerus eremicus under two different climate scenarios

Whiteflies (Aleyrodidae) cause high economic losses in agricultural systems worldwide. Heavy reliance on insecticide use for whitefly control has led to the resistance development towards nearly all used groups of insecticides. A more sustainable, widely used, and irreplaceable control measure in protected cropping systems is biological control by augmentative release of parasitoids. All commercially available whitefly parasitoids are wasps from the genera Encarsia and Eretmocerus, with one of the most used parasitoid species being Eretmocerus eremicus. Biocontrol by these highly specialized natural enemies is sensitive to changes in environmental conditions. Ongoing anthropogenic climate change could affect multitrophic interactions between organisms, and biocontrol systems are not an exception. At the same time, little is known about the development of E. eremicus under projected future climate conditions. The present study evaluates the longevity of this important biocontrol agent by performing climatic chamber simulation driven by physically consistent, regionally downscaled, multi-model ensemble projections of the future climate for Luxembourg. Results show a reduction of its longevity up to 50% under future climate. The median survival in the projected future climate was found to be 13 days, which is 9 days less than under present climate. Implications on the efficacy of the whitefly biocontrol practices in future climate conditions are discussed.

A methodical survey of mathematical model-based control techniques based on open and closed loop control approach for diabetes management

Disturbance of blood sugar level is controlled through well-known biomechanical feedback loops: high levels of glucose in blood facilitate to release insulin from the pancreas which accelerates the absorption rate of cellular glucose. Low glucose levels encourage to release pancreatic glucagon which induces glycogen breakdown to glucose in the liver. These bio-control systems do not function properly in diabetic patients. Though the control of disease seems intuitively easy, in real life, due to many differences in structure by diet and fasting, exercise, medications, patient’s profile and other stressors, it is not that easy. The mathematical models of the glucose-insulin regulatory system follow the patient’s physiological conditions which make it difficult to identify and estimate all the model parameters. In this paper, we have given a systematic literature review on mathematical models of the diabetic patients, and various kinds of disease control techniques through the development of open and closed loop insulin deliver command system and optimization of exogenous insulin rate. It demonstrates the open and closed loop type model-based control strategies underlying the assumptions of the concerned models. The combination of mathematical model with control strategies such as genetic algorithm (GA), neural network (NN), sliding mode controller (SMC), model predictive controller (MPC), and fuzzy logic control (FLC) has been considered, which provides an overview of this area, highlighting the control profile over the diabetic model with promising clinical results, outlining key challenges, and identifying needs for the future research. Also, the significance of these control algorithms has been discussed in the presence of the noises, the controller’s robustness and various other disturbances. It provides substantial information on diabetes management through various control techniques.

Assessing Genotypic and Environmental Effects on Endophyte Communities of Fraxinus (Ash) Using Culture Dependent and Independent DNA Sequencing.

Fraxinus excelsior populations are in decline due to the ash dieback disease Hymenoscyphus fraxineus. It is important to understand genotypic and environmental effects on its fungal microbiome to develop disease management strategies. To do this, we used culture dependent and culture independent approaches to characterize endophyte material from contrasting ash provenances, environments, and tissues (leaves, roots, seeds). Endophytes were isolated and identified using nrITS, LSU, or tef DNA loci in the culture dependent assessments, which were mostly Ascomycota and assigned to 37 families. Few taxa were shared between roots and leaves. The culture independent approach used high throughput sequencing (HTS) of nrITS amplicons directly from plant DNA and detected 35 families. Large differences were found in OTU diversity and community composition estimated by the contrasting approaches and these data need to be combined for estimations of the core endophyte communities. Species richness and Shannon index values were highest for the leaf material and the French population. Few species were shared between seed and leaf tissue. PCoA and NMDS of the HTS data showed that seed and leaf microbiome communities were highly distinct and that there was a strong influence of Fraxinus species identity on their fungal community composition. The results will facilitate a better understanding of ash fungal ecology and are a step toward identifying microbial biocontrol systems to minimize the impact of the disease.

Insights Into the Establishment of Introduced Species Using Coccinellines (Coleoptera: Coccinellidae) as a Model System

Species introductions occur around the world both inadvertently and deliberately (typically for conservation, agriculture or fisheries). However, not all introduced species become established. Understanding the factors that affect the establishment success of introduced species will help us improve species introductions for biocontrol and conservation purposes. Here we argue that important generalist arthropod predators, the Coccinellini ladybirds (Coleoptera: Coccinellidae), are an ideal taxon for investigating the establishment process of introduced species. Coccinellini are introduced accidently via plant exports, as well as deliberately as biocontrol agents to reduce agricultural pests, and a few have become invasive species. Here, using work from invasive biology and biocontrol systems, we categorize the factors affecting the successful establishment of introduced species. These factors are 1) invasiveness of the species, 2) invasibility of the recipient ecosystem and 3) stochastic events that occur after the introduction. We review how factors such as diet and competition, dispersal ability, propagule population, disturbances and climate change can be studied within these three categories to better predict the establishment success of introduced ladybirds. Our review highlights that our current understanding of the differences between successful and unsuccessful species establishments is limited. To address this, we need direct comparisons of dispersal ability and both interspecific and intraspecific variation in ladybirds. We conclude that studies of ladybirds will help to develop theories that better characterize and predict establishment success and invasive potential.

Поглощение витального красителя байкальской губкой как тест-отклик на воздействие ПАВ

Baikal sponges account for a large, if not the largest proportion of zoobenthos of Lake Baikal, especially in the littoral. It is here that the largest number of pollutants comes. A fixed lifestyle, inertia, and the absence of visible manifestations of the life activity of the sponges create significant specific difficulties when working with them in a laboratory experiment. The lack of clear criteria, test reactions, and rapid biocontrol systems hinder the determination of the physiological state of the sponges, their activity, degree of infection, cure, and the influence of various stress factors on them. In this regard, there is relatively little information about the reactions of Baikal Porifera to toxicants. This report presents experimental materials on the change in dye absorption by Baicalospongia bacilifera sponge under the influence of one of the most common components of domestic wastewater – sodium dodecyl sulfate. A negative effect was noted with a 2-hour exposure to the sponge of this surfactant in a concentration of 25 mg/l and higher. The obtained experimental data suggest that, in further studies, bleaching of dye solutions with a sponge of B. bacilifera can serve as a test reaction for the presence of contaminants.

Bugs scaring bugs: enemy-risk effects in biological control systems.

Enemy‐risk effects, often referred to as non‐consumptive effects (NCEs), are an important feature of predator–prey ecology, but their significance has had little impact on the conceptual underpinning or practice of biological control. We provide an overview of enemy‐risk effects in predator–prey interactions, discuss ways in which risk effects may impact biocontrol programs and suggest avenues for further integration of natural enemy ecology and integrated pest management. Enemy‐risk effects can have important influences on different stages of biological control programs, including natural enemy selection, efficacy testing and quantification of non‐target impacts. Enemy‐risk effects can also shape the interactions of biological control with other pest management practices. Biocontrol systems also provide community ecologists with some of the richest examples of behaviourally mediated trophic cascades and demonstrations of how enemy‐risk effects play out among species with no shared evolutionary history, important topics for invasion biology and conservation. We conclude that the longstanding use of ecological theory by biocontrol practitioners should be expanded to incorporate enemy‐risk effects, and that community ecologists will find many opportunities to study enemy‐risk effects in biocontrol settings.

The postharvest microbiome: The other half of sustainability

Biological control of postharvest diseases has been suggested as a viable alternative to synthetic chemicals and has been the focus of considerable research worldwide for the last 30 years by many scientists and several commercial companies. Microbiome-based research has opened a whole new frontier that will greatly expand our knowledge of postharvest pathology and biology and offer new opportunities for developing novel approaches for biocontrol that are based on a deeper understanding of the complex interactions taking place between the resident microbiota and harvested produce. The postharvest microbiome is only beginning to be explored and the composition and functional effect of the microbiome on fresh produce after harvest is largely unknown. Determining if different commodities have a core microbiome that influences potential host-microbiome interactions has yet to be determined. Viewing harvested produce as a meta-organism, within the holobiont concept, and its recent iterations, may represent a useful model for the postharvest microbiome considering that harvested commodities represent dynamic systems with complex microbial community-host interactions. Understanding the functional role and impact of the endophytic and epiphytic microbiome of developing and harvested fruit would provide valuable information needed for the development of safe and effective, function-based biocontrol systems that can be used to enhance the shelf life of produce by controlling decay pathogens and perhaps even postharvest physiological disorders.

The fruit microbiome: A new frontier for postharvest biocontrol and postharvest biology

Microorganisms are an integral part of the composition of fruits and vegetables and are found as epiphytes on the surface or as endophytes within tissues. The realization that fruit surfaces harbor beneficial microorganisms fostered the field of biological control using epiphytic microorganisms which led to the development of several commercial biocontrol products. Advances in DNA sequencing and “omics” technologies have enhanced our ability to characterize the diversity and function of microbial communities (microbiome) present in and on plant tissues. Microbiome studies have the potential of providing knowledge that will lead to a fundamental paradigm shift in the way we think about biocontrol strategies, biocontrol products, and postharvest biology, as well as the health attributes of fruits and vegetables. Fruit microbiome research will enhance our understanding of harvested commodities as an ecosystem in which the microbiome plays an essential role in the health and physiology of fruit after it is harvested. Meta-omic (metagenomics, metatranscriptomics, metaproteomics, and metametabolomics) technologies are only beginning to be applied to postharvest studies and will revolutionize our understanding of postharvest biocontrol systems, foodborne pathogens, and postharvest physiology. The role of the microbiome in plant health, productivity, and cultivar development should be considered as much as the plant itself. Plant breeding or genetic modification of plants could be used to intentionally modulate the composition of the microbiome and its function, recruiting disease antagonists and plant-growth promoters that enhance plant health and the quality of the harvested products. Increased knowledge of microbial community systems will lead to the development of natural or synthetic consortia that can be used to prevent postharvest diseases and mitigate physiological disorders in harvested commodities.

Rethinking biological control programs as planned invasions.

Biological control of pests with their natural enemies essentially consists of planned invasions, with the opportunity to select both the invader and the invaded environment. Recent advances in invasion science link 'intrinsic invasion factors' (life history and behavioral traits) with invader success; connect 'extrinsic invasion factors' (abiotic and biotic aspects of the invaded environment) with environmental invasibility; and demonstrate that their interaction leads not only to ecologically driven variability but also to rapid evolutionary change in biocontrol systems. However, current theory and empirical evidence from invasion science have not yet been extensively adopted into biological control research and practice.

The biocontrol agent Pseudomonas chlororaphis PA23 primes Brassica napus defenses through distinct gene networks

BackgroundThe biological control agent Pseudomonas chlororaphis PA23 is capable of protecting Brassica napus (canola) from the necrotrophic fungus Sclerotinia sclerotiorum via direct antagonism. While we have elucidated bacterial genes and gene products responsible biocontrol, little is known about how the host plant responds to bacterial priming on the leaf surface, including global changes in gene activity in the presence and absence of S. sclerotiorum.ResultsApplication of PA23 to the aerial surfaces of canola plants reduced the number of S. sclerotiorum lesion-forming petals by 91.1%. RNA sequencing of the host pathogen interface showed that pretreatment with PA23 reduced the number of genes upregulated in response to S. sclerotiorum by 16-fold. By itself, PA23 activated unique defense networks indicative of defense priming. Genes encoding MAMP-triggered immunity receptors detecting flagellin and peptidoglycan were downregulated in PA23 only-treated plants, consistent with post-stimulus desensitization. Downstream, we observed reactive oxygen species (ROS) production involving low levels of H2O2 and overexpression of genes associated with glycerol-3-phosphate (G3P)-mediated systemic acquired resistance (SAR). Leaf chloroplasts exhibited increased thylakoid membrane structures and chlorophyll content, while lipid metabolic processes were upregulated.ConclusionIn addition to directly antagonizing S. sclerotiorum, PA23 primes the plant defense response through induction of unique local and systemic defense networks. This study provides novel insight into the effects of biocontrol agents applied to the plant phyllosphere. Understanding these interactions will aid in the development of biocontrol systems as an alternative to chemical pesticides for protection of important crop systems.

Biological Control of Aflatoxin Contamination in U.S. Crops and the Use of Bioplastic Formulations of Aspergillus flavus Biocontrol Strains To Optimize Application Strategies.

Aflatoxin contamination has a major economic impact on crop production in the southern United States. Reduction of aflatoxin contamination in harvested crops has been achieved by applying nonaflatoxigenic biocontrol Aspergillus flavus strains that can out-compete wild aflatoxigenic A.flavus, reducing their numbers at the site of application. Currently, the standard method for applying biocontrol A.flavus strains to soil is using a nutrient-supplying carrier (e.g., pearled barley for Afla-Guard). Granules of Bioplastic (partially acetylated corn starch) have been investigated as an alternative nutritive carrier for biocontrol agents. Bioplastic granules have also been used to prepare a sprayable biocontrol formulation that gives effective reduction of aflatoxin contamination in harvested corn kernels with application of much smaller amounts to leaves later in the growing season. The ultimate goal of biocontrol research is to produce biocontrol systems that can be applied to crops only when long-range weather forecasting indicates they will be needed.

Unraveling the mechanisms used by antagonistic yeast to control postharvest pathogens on fruit

Biological control using microbial antagonists is one of the most promising alternatives for reducing fungicide use during the postharvest life of fruits. To date, there are hundreds of reports about using yeast antagonists to control biologically postharvest diseases. Very few of these antagonists, however, have reached the commercial development stage and launched as commercial products. In most cases, there are inherent problems in the biocontrol systems related to poor performance and inconsistency under commercial conditions. Among the reasons for these shortcomings is the lack of understanding of mechanisms of actions of these BCAs. A deep understanding of the mode of action is essential to develop appropriate formulation and methods of application, and to obtain registration. In recent years, there has been a phenomenal advancement in the use of molecular techniques contributing to the development of innovative tools for improving knowledge on the antagonistic mechanisms of BCAs. In particular, the omics techniques are providing a powerful tool to dissect the complex interactions between the antagonist, the pathogen, the fruit host, the natural microflora, and the environmental conditions.

Breaking and remaking a seed and seed predator interaction in the introduced range of Scotch Broom (Cytisus scoparius) in New Zealand

Summary Introduced plants may initially experience enemy release, but some of those interactions may be reinstated through biological control. These cases provide opportunities to explore the dynamics of broken and remade consumer–resource interactions. The European shrub broom (Cytisus scoparius) was introduced to New Zealand without a specialist seed predator (Bruchidius villosus) until a biological control programme reinstated this interaction in 1988. Broom produces substantially larger seeds throughout its non‐native range, and there are differences in seedling establishment beneath broom canopies between the native and introduced ranges. We hypothesized that large broom seeds produce seedlings with a survival advantage in shaded conditions, consistent with establishment under broom canopies in the introduced range. We also predicted that the seed‐feeding beetle would experience increased fitness in larger seeds. We found that seedling survival was correlated with seed weight in shaded conditions, consistent with the observed establishment of seedlings beneath broom stands in the non‐native range. Beetle size was positively correlated with seed weight, and female fecundity increased with body size. Comparison of the size distributions of beetle populations before and after hibernation provided indirect evidence that overwintering survival of beetles is also size‐dependent. These findings are consistent with observed higher levels of abundance of B. villosus in New Zealand, compared to native habitats. Selection gradients for seed size‐dependent seedling survival on broom occupancy were explored using the Rees–Paynter population model, demonstrating that a fitness benefit to the plant of large seed size through enhanced seedling survival beneath the parental canopy is only likely under low‐disturbance scenarios and moderate fecundity levels. Synthesis. The dynamics of biocontrol systems provide an underexploited opportunity to examine the impact of removal and reinstatement of species interactions. Differences in seed size between native and non‐native ranges may result from varying intensities of conflicting selection pressures acting on seed size. It remains to be seen whether a decline in seed size towards that seen in the native range will result from the biocontrol agent introduction, as we have demonstrated that selection pressures on seed size vary with disturbance‐mediated population turnover and fecundity.