Biological Control Strategies Research Articles

Could Bacillus biofilms enhance the effectivity of biocontrol strategies in the phyllosphere?

Maize (Zea mays L.), a major crop in Argentina and a staple food around the world, is affected by the emergence and re-emergence of foliar diseases. Agrochemicals are the main control strategy nowadays; however, they can cause resistance in insects and microbial pathogens and have negative effects on the environment and human health. An emerging alternative is the use of living organisms, i.e. microbial biocontrol agents, to suppress plant pathogen populations. This is a risk-free approach when the organisms acting as biocontrol agents come from the same ecosystem as the foliar pathogens they are meant to antagonize. Some epiphytic microorganisms may form biofilm by becoming aggregated and attached to a surface, as is the case of spore-forming bacteria from the genus Bacillus. Their ability to sporulate and their tolerance to long storage periods make them a frequently used biocontrol agent. Moreover, the biofilm that they create protects them against different abiotic and biotic factors and helps them to acquire nutrients, which ensures their survival on the plants they protect. This review analyzes the interactions that the phyllosphere-inhabiting Bacillus genus establishes with its environment through biofilm, and how this lifestyle could serve to design effective biological control strategies.

Biocontrol: Endophytic bacteria could be crucial to fight soft rot disease in the rare medicinal herb, Anoectochilus roxburghii.

Microbial destabilization induced by pathogen infection has severely affected plant quality and output, such as Anoectochilus roxburghii, an economically important herb. Soft rot is the main disease that occurs during A. roxburghii culturing. However, the key members of pathogens and their interplay with non-detrimental microorganisms in diseased plants remain largely unsolved. Here, by utilizing a molecular ecological network approach, the interactions within bacterial communities in endophytic compartments and the surrounding soils during soft rot infection were investigated. Significant differences in bacterial diversity and community composition between healthy and diseased plants were observed, indicating that the endophytic communities were strongly influenced by pathogen invasion. Endophytic stem communities of the diseased plants were primarily derived from roots and the root endophytes were largely derived from rhizosphere soils, which depicts a possible pathogen migration image from soils to roots and finally the stems. Furthermore, interactions among microbial members indicated that pathogen invasion might be aided by positively correlated native microbial members, such as Enterobacter and Microbacterium, who may assist in colonization and multiplication through a mutualistic relationship in roots during the pathogen infection process. Our findings will help open new avenues for developing more accurate strategies for biological control of A. roxburghii bacterial soft rot disease.

Biocontrol of Candida albicans by Antagonistic Microorganisms and Bioactive Compounds

Candida albicans is an endogenous opportunistic pathogenic fungus that is harmless when the host system remains stable. However, C. albicans could seriously threaten human life and health when the body’s immune function declines or the normal flora is out of balance. Due to the increasing resistance of candidiasis to existing drugs, it is important to find new strategies to help treat this type of systemic fungal disease. Biological control is considered as a promising strategy which is more friendly and safer. In this review, we compare the bacteriostatic behavior of different antagonistic microorganisms (bacteria and fungi) against C. albicans. In addition, natural products with unique structures have attracted researchers’ attention. Therefore, the bioactive nature products produced by different microorganisms and their possible inhibitory mechanisms are also reviewed. The application of biological control strategies and the discovery of new compounds with antifungal activity will reduce the resistance of C. albicans, thereby promoting the development of novel diverse antifungal drugs.

Entomopathogenic fungi and Schinus molle essential oil: The combination of two eco-friendly agents against Aedes aegypti larvae

Aedes aegypti transmits arbovirus, which is a public health concern. Certain filamentous fungi have the potential to control the disease. Here, the effects of Metarhizium anisopliae s.l. CG 153, Beauveria bassiana s.l. CG 206 and Schinus molle L. were investigated against Aedes aegypti larvae. In addition, the effect of essential oil on fungal development was analyzed. Fungal germination was assessed after combination with essential oil at 0.0025 %, 0.0075 %, 0.005 %, or 0.01 %; all of the oil concentrations affected germination except 0.0025 % (v/v). Larvae were exposed to 0.0025 %, 0.0075 %, 0.005 %, or 0.01 % of the essential oil or Tween 80 at 0.01 %; however, only the essential oil at 0.0025 % achieved similar results as the control. Larvae were exposed to fungi at 107 conidia mL-1 alone or in combination with the essential oil at 0.0025 %. Regardless of the combination, M. anisopliae reduced the median survival time of mosquitoes more than B. bassiana. The cumulative survival of mosquitoes exposed to M. anisopliae alone or in combination with essential oil was 7.5 % and 2 %, respectively, and for B. bassiana, it was 75 % and 71 %, respectively. M. anisopliae + essential oil had a synergistic effect against larvae, whereas B. bassiana + essential oil was antagonistic. Scanning and transmission electron microscopy, and histopathology confirmed that the interaction of M. anisopliae was through the gut and hemocoel. In contrast, the mosquito’s gut was the main route for invasion by B. bassiana. Results from gas chromatography studies demonstrated sabinene and bicyclogermacrene as the main compounds of S. molle, and the in-silico investigation found evidence that both compounds affect a wide range of biological activity. For the first time, we demonstrated the potential of S. molle and its interaction with both fungal strains against A. aegypti larvae. Moreover, for the first time, we reported that S. molle might be responsible for significant changes in larval physiology. This study provides new insights into host-pathogen interplay and contributes to a better understanding of pathogenesis in mosquitoes, which have significant consequences for biological control strategies.

An optimal control problem for dengue transmission model with Wolbachia and vaccination

The release of Wolbachia-infected mosquitoes into the wild mosquitoes population is an excellent biological control strategy which can be effective against mosquito-borne infections. In this work, we propose a dengue transmission model that incorporates releasing Wolbachia into the wild mosquito population and vaccinating human population. We analyze the basic reproduction number, the existence and stability of the equilibria, and carry out the sensitivity analysis to quantify the effects of parameters on the basic reproduction number. The analysis shows that the basic reproduction number determines the stability of two equilibria, and two transmission probabilities are positively correlated with the basic reproduction number, especially, the transmission probability of human being infected byWolbachia-infected mosquitoes is more sensitive than that of wild mosquitoes. Based on an integrated control strategy for the prevention of dengue fever (vaccination, using mosquito nets, improved treatment of dengue and spraying insecticides), we derive the necessary conditions for the optimal control problem using Pontryagin’s Maximum Principle and carry out numerical simulations by MATLAB. Finally, the cost-effectiveness analysis of several control strategies is examined to determine the most feasible strategy. It shows that the most cost-effective integrated strategy is vaccination, using mosquito nets and spraying insecticides.

Disentangling arthropod and plant resources consumed by Orius spp. in peach and alfalfa crops by metagenomic analysis

Agricultural intensification is affecting the biological control of insect pests, an important component for sustainable crop production. To understand the changing patterns of insect abundance within an agroecosystem, it is necessary to disentangle the trophic interactions between species, and metabarcoding is an excellent alternative to show them. In the Ebro Basin (NE Iberian Peninsula), agricultural landscapes are composed of a mosaic of crops scattered with natural and semi-natural habitats, where the presence of Orius spp., used as biocontrol agents, is well known. To shed light on their predatory role in this area, a previously developed metabarcoding multi-primer method has been used to study the arthropod and plant most frequently resources consumed by some field-collected Orius, sampled at different dates in a peach and an alfalfa adjacent crop. Their high-throughput sequencing (HTS) analysis showed the consumption of 15 arthropod and 12 plant taxa. Eight of them were consumed by O. laevigatus, six by O. majusculus and 23 by O. niger. The obtained results showed that HTS is a powerful tool in studies of trophic interactions in agroecosystems. Among the detected arthropods, other natural enemies were present, showing a certain degree of intraguild predation, which has been demonstrated by developing a new added strategy in the bioinformatic analysis. Detected plant consumption indicates that Orius forages on several plant species, showing their movement from them to the sampled crops. These plants could have a potential role in attracting or maintaining these predators in both crops in biological control strategies.

The Synthesis and Assembly of a Truncated Cyanophage Genome and Its Expression in a Heterogenous Host.

Cyanophages play an important role in regulating the dynamics of cyanobacteria communities in the hydrosphere, representing a promising biological control strategy for cyanobacterial blooms. Nevertheless, most cyanophages are host-specific, making it difficult to control blooming cyanobacteria via single or multiple cyanophages. In order to address the issue, we explore the interaction between cyanophages and their heterologous hosts, with the aim of revealing the principles of designing and constructing an artificial cyanophage genome towards multiple cyanobacterial hosts. In the present study, we use synthetic biological approaches to assess the impact of introducing a fragment of cyanophage genome into a heterologous cyanobacterium under a variety of environmental conditions. Based on a natural cyanophage A-4L genome (41,750 bp), a truncated cyanophage genome Syn-A-4-8 is synthesized and assembled in Saccharomyces cerevisiae. We found that a 351–15,930 bp area of the A-4L genome has a fragment that is lethal to Escherichia coli during the process of attempting to assemble the full-length A-4L genome. Syn-A-4-8 was successfully introduced into E. coli and then transferred into the model cyanobacterium Synechococcus elongatus PCC 7942 (Syn7942) via conjugation. Although no significant phenotypes of Syn7942 carrying Syn-A-4-8 (LS-02) could be observed under normal conditions, its growth exhibited a prolonged lag phase compared to that of the control strain under 290-millimolar NaCl stress. Finally, the mechanisms of altered salt tolerance in LS-02 were revealed through comparative transcriptomics, and ORF25 and ORF26 on Syn-A-4-8 turned out to be the key genes causing the phenotype. Our research represents an important attempt in designing artificial cyanophages towards multiple hosts, and offers new future insights into the control of cyanobacterial blooms.

Screening and efficacy evaluation of antagonistic fungi against Phytophthora infestans and combination with arbuscular mycorrhizal fungi for biocontrol of late blight in potato

Late blight caused by Phytophthora infestans is the most devastating disease of potato crops worldwide. Control practices mostly rely on synthetic fungicides or copper-based products. In recent years, biological control agents have generated significant enthusiasm as eco-friendly sustainable alternatives. Here, the filtrates of 149 filamentous fungi and yeasts were tested in vitro against P. infestans MUCL 54981. The most effective filtrates were then combined in alginate beads with the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis MUCL 41833 and tested in vitro for their compatibility, and finally in the greenhouse for their efficacy against P. infestans. The filtrates of Penicillium aurantiogriseum MUCL 47586, Penicillium griseofulvum MUCL 29201, Trichoderma virens MUCL 18139, and Verticillium psalliotae MUCL 18310 totally suppressed conidial germination and growth of P. infestans in vitro. In whole potato plants in vitro, only the filtrate of T. virens significantly suppressed P. infestans plant infestation. With the exception of P. griseofulvum, none of the selected filtrates affected the germination, root colonization, and spore production of R. irregularis following their combined entrapment in alginate beads. According to these results, the filtrate of T. virens was selected for the greenhouse experiment with the potato variety Annabelle. The filtrate was used as leaf spray and/or as root treatment in combination with R. irregularis entrapped in alginate beads. Root treatments with AMF alone as well as with the AMF entrapped with the filtrate of T. virens significantly reduced the area under disease progress curve compared to the non-treated plants. LC-MS analyses of the filtrate showed the production of koninginin D, gliotoxin, and koningic acid, three antifungal compounds, which could have impacted P. infestans. Conversely, foliar application of the filtrate, whether the plant was colonized by the AMF or not, did not reduce symptoms of the disease, possibly because of the greenhouse growth conditions making the potato plants more susceptible to P. infestans and counterbalancing the positive effects of the antimicrobial secondary metabolites or AMF. Our results demonstrated the potential of R. irregularis MUCL 41833 combined or not with a filtrate of T. virens MUCL 18139 into alginate beads as a biological control strategy against P. infestans.

Microbiota Communities of Healthy and Bacterial Pustule Diseased Soybean.

Soybean is an important source of protein and for a wide range of agricultural, food, and industrial applications. Soybean is being affected by Xanthomonas citri pv. glycines, a causal pathogen of bacterial pustule disease, result in a reduction in yield and quality. Diverse microbial communities of plants are involved in various plant stresses is known. Therefore, we designed to investigate the microbial community differentiation depending on the infection of X. citri pv. glycines. The microbial community’s abundance, diversity, and similarity showed a difference between infected and non-infected soybean. Microbiota community analysis, excluding X. citri pv. glycines, revealed that Pseudomonas spp. would increase the population of the infected soybean. Results of DESeq analyses suggested that energy metabolism, secondary metabolite, and TCA cycle metabolism were actively diverse in the non-infected soybeans. Additionally, Streptomyces bacillaris S8, an endophyte microbiota member, was nominated as a key microbe in the healthy soybeans. Genome analysis of S. bacillaris S8 presented that salinomycin may be the critical antibacterial metabolite. Our findings on the composition of soybean microbiota communities and the key strain information will contribute to developing biological control strategies against X. citri pv. glycines.

Bioassays of Beauveria bassiana Isolates against the Fall Armyworm, Spodoptera frugiperda.

The control of Spodoptera frugiperda, the key invasive pest of maize, is a serious concern due to its biology and the current global restriction on applying synthetic pesticides. Entomopathogenic fungi are considered to be a potential biological control strategy. The pathogenicity of 12 isolates of Beauveria bassiana in the immature stages and feeding efficacy of S. frugiperda were evaluated. The B. bassiana isolates QB-3.45, QB-3.46 and QB-3.428 caused the highest egg mortality rates of 87.3, 82.7 and 79.3%, respectively, when applied at a concentration of 1 × 108 conidia/mL and measured at 7 days post-treatment. Neonate mortality rates of 45.6 to 53.6% were observed with the same isolates. The B. bassiana isolates caused significant cumulative mortality rates ranging from 71.3 to 93.3% at 14 days post-treatment and reduced larval feeding efficacy from 69.4 to 77.8% at 48 h post-treatment. This study supports using the effective B. bassiana isolates as a biological control agent against S. frugiperda. The significant mortality of the eggs and neonatal larvae and the reduction in the feeding efficacy of the second instar larvae of the S. frugiperda that were treated with isolates of B. bassiana supports the application of entomopathogenic fungi as a biocontrol agent for the effective control of the S. frugiperda population.

The kairomone p-anisaldehyde increases the effectiveness of sticky traps for capturing Neohydatothrips signifer (Insecta: Thysanoptera) in yellow passion fruit (Passiflora edulis) crops

Thrips are important pest species in a wide variety of crops. Their cryptic behavior imposes a challenge for damage detection and population control with traditional methods (e.g., insecticides). Although the exploitation of chemical ecology strategies for thrip monitoring and mass-trapping is relatively widespread, the research in this regard in Neotropical regions is still scanty. In this study, we conducted a field experiment to test whether the kairomonep-anisaldehyde would increase the effectiveness of sticky traps for controlling (masstrapping) the thrip Neohydatothrips signifier. We found out that sticky traps equipped with the kairomone collected more thrips (nymphs + adults) through time, and this effect was not dependant on trap height. Additionally, we demonstrated that thrip incidence was quickly reduced in Passiflora edulis plants when surrounded by kairomone-containing sticky traps. Our results highlight the benefit of using kairomones in the integrated pest management programs for N. signifier as a straightforward selective method compatible with biological and chemical control strategies.

Trichoderma Enzymes for Degradation of Aflatoxin B1 and Ochratoxin A.

The contamination of agricultural products with mycotoxins causes risks to animal and human health and severe economic losses. Mycotoxicoses can be reduced by preventing fungal infection using chemical and biological approaches. The chemical strategies can release toxic molecules; therefore, strategies for biological control are being evaluated, such as using nontoxic fungi and their metabolites. This work evaluated the effect of exoenzymes produced by the beneficial fungus Trichoderma afroharzianum strain T22 in degrading Aflatoxin B1 (AFB1) and Ochratoxin A (OTA). The ability of Trichoderma to produce hydrolases was stimulated by using different inducing substrates. The highest AFB1 and OTA degradation activity was obtained using a medium containing lyophilized mushrooms and crude fiber. The T. afroharzianum T22’s ability to reduce mycotoxins may be attributed to peroxidase enzymes. This study showed that T. afroharzianum strain T22 or its peroxidase supplementation could represent a sustainable strategy for the degradation of AFB1 and OTA in feed and food products.

Management of potato cyst nematodes with special focus on biological control and trap cropping strategies.

Potato cyst nematodes (PCNs; Globodera spp.) are one of the most difficult pests of potato to manage worldwide. Indiscriminate use of pesticides and their hazardous effects discourage the use of many chemicals for the management of PCNs. As a result, biological control agents and trap crops have received more attention from growers as safer ways to manage PCNs. The biological control agents such as Pochonia chlamydosporia, Purpureocillium lilacinum, Trichoderma spp., Pseudomonas fluorescens, Bacillus spp., Pasteuria spp., and others are recognized as potential candidates for the management of PCNs. Moreover recently, the use of trap crop Solanum sisymbriifolium also showed promise by drastically reducing soil populations of PCNs. Integration of these management strategies along with other practices including identification, conservation, and multiplication of native antagonists, will facilitate efficient management of the PCNs in potato cropping system. Some of the promising research approaches that are being used against PCNs are addressed in this review. © 2022 Society of Chemical Industry.

Virulence of native isolates of entomopathogenic fungi (Hypocreales) against the “sweetpotato whitefly” Bemisia tabaci (Hemiptera: Aleyrodidae), including the effects of temperature and fungicides

Hypocrella, Moelleriella and related species in the Hypocreales (Ascomycota, Sordariomycetes) cause epizootics of whiteflies and scale insects in nature. However, studies on their host specificity, virulence, infection cycles, optimal development under laboratory conditions, and compatibility with other control methods, are unexplored for most species. Under laboratory conditions, the virulence of several isolates of field-collected hypocrealean fungi (Hypocrella, Moelleriella, Regiocrella, and Verticillium) was determined on Bemisia tabaci eggs and 4th instar nymphs. In addition to virulence, the effect of temperature and two commercial fungicides on growth rates and germination of the isolates was evaluated. None of the isolates infected the eggs, while M. libera, M. ochracea, and M. turbinata caused high nymphal mortality. Moelleriella libera was the most virulent isolate. At all temperatures, M. libera, Regiocrella sp. (P17H20), and Verticillium cf. pseudohemipterigenum had the highest germination and growth rates. The optimal growth temperature depended on the isolate, but at 23 °C and 25 °C, the probability of spore germination was higher for most isolates. Finally, the fungicides azoxystrobin and chlorothalonil inhibited growth rates and conidial germination at 24 and 48 h of exposure. This research produces vital knowledge on the virulence and infection cycles of poorly studied native species of entomopathogenic fungi. In addition, the results provide information on the optimal temperature for development in laboratory conditions and susceptibility to fungicides, which could contribute to future biological control strategies.

Predator-prey interactions and life history of Orius laevigatus and O. majusculus feeding on flower and leaf-inhabiting thrips

Thrips (Thysanoptera: Thripidae) are major pests in horticulture worldwide. Longstanding biological control strategies that have been developed for flower thrips such as Frankliniella occidentalis (Pergande) are being disrupted by the recent introduction of leaf-inhabiting thrips such as Echinothrips americanus Morgan and Thrips setosus Moulton in Northern Europe. In this study, we evaluated the predator–prey interactions, predation capacity, juvenile development and adult reproduction of the two commercial anthocorid predators Orius laevigatus (Fieber) and Orius majusculus (Reuter) (Hemiptera: Anthocoridae) on these thrips. In behavioral assays, predators were more successful in subduing and consuming sedentary leaf-inhabiting thrips adults compared to the highly mobile F. occidentalis. Furthermore, O. laevigatus was more successful in subduing prey compared to the bigger predator O. majusculus. Female adults of O. laevigatus and O. majusculus killed 18 and 20 F. occidentalis adults, respectively, in 24 h, while the kill rate was around two times higher when predators were offered E. americanus or T. setosus as prey. Developmental and reproductive parameters of both Orius predators were more favorable when feeding on the leaf-inhabiting thrips compared to F. occidentalis. This was further evident in the higher intrinsic rates of increase (rm) we recorded on a diet of E. americanus compared to F. occidentalis (0.162 and 0.148 females/female/day for O. laevigatus, respectively; 0.148 and 0.127 for O. majusculus, respectively). Our findings show that E. americanus and T. setosus constitute high quality prey for anthocorid predators, highlighting the potential of these predators for effective pest control.

Factors Influencing the Efficacy of Biological Control Agents Used to Manage Insect Pests in Indoor Cannabis (Cannabis sativa) Cultivation

Current biological control strategies in cannabis (Cannabis sativa) cultivation have resulted in poor efficacy for managing certain insect pests. The cannabis industry has grown at a rapid pace, surpassing our ability to develop knowledge on the production systems for this crop. Currently, the research focus is on optimizing agronomic and environmental factors to maximize the yield and quality of cannabis. However, cannabis growers are increasingly challenged by severe insect pest pressure, with few effective options. Decades of research have optimized biological control strategies in other crops. The implementation of effective biological control strategies in cannabis is hindered by a variety of morphological, biochemical, and agronomic factors unique to this crop. Here, we review the rather limited literature relevant to insect pest management in indoor cannabis production. Further, we have identified three factors that we believe are primarily responsible for the ineffectiveness of biological control in cannabis: Plant morphology including trichome density and floral resources, effects of plant biochemistry on prey suitability, and finally the effects of supplemental lighting including photoperiod, intensity, and spectrum. We highlight the importance of prioritizing the evaluation of these factors to improve our understanding of the tritrophic interactions governing the success of biological control in cannabis cultivation. As intensive research efforts are underway to optimize agronomic practices for cannabis, it is also important to consider their relevance to biological control.

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

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

New insights from the virome of Halyomorpha halys (Stål, 1855)

Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae), the brown marmorated stink bug, is an invasive pentatomid native to East-Asia, and introduced worldwide in recent times. It is a polyphagous pest with approximately 300 host plants, which, due to its plasticity, reproductive and feeding behavior, long-distance flight, and walking as well as human-mediated dispersal ability, is able to cause significant economic and ecological damage. In several cases pest control mediated by insecticide treatments leads to unsatisfactory efficacy, mostly due to insect recovery ability. Thus, the most promising method for the long-term management of this pest has been focused with growing emphasis on classical biological control strategies. In this framework, viruses have untill now been poorly investigated in H. halys with only a single virus described from the US territory. For this reason we investigated the virome associated with a small and well described population of H. halys from Piedmont (Italy) describing for the first time 7 new viral sequences belonging to different taxonomical groups. Further studies will be necessary to assess the biological and ecological effects the viruses have on their host. Due to the agricultural importance of this insect, the biological characterization of these viruses would give important information on the possibility to exploit viral entities as biological control agents. Finally, the presence of a such relevant number of viruses from a small population suggests a wide association between the brown marmorated stink bug and viral entities. Further studies to determine the possible exploitation of viral sequences to trace different populations are ongoing.

The effect of host plant on the biological control efficacy of the predatory mite, Phytoseiulus persimilis Athias-Henriot against two-spotted spidermites, Tetranychus urticae koch on field-grown vegetables

Tetranychus urticae Koch (Acari: Tetranychidae) is one of the key pests causing economic losses in vegetable fields. Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) is used effectively in the biological control of this mite on many vegetable crops. The present study determined how different crops such as pepper, eggplant, cucumber and tomato affected the biological control of T. urticae when using P. persimilis in the field-grown vegetables in the Çanakkale of northwestern part of Turkey in 2016 and 2017. Predatory and prey mites were released at a ratio of 1:10 predator:prey on host plants and their numbers on leaves were counted weekly for a period of 8 weeks. The highest number of T. urticae and P. persimilis were counted on cucumber with 108.70 ± 8.14 and 81.00 ± 6.00 mites per leaf in 2016, and with 113.30 ± 10.95 and 24.00 ± 4.58 mites per leaf in 2017, respectively. Also, there was a significant difference for both the populations of T. urticae and P. persimilis on the crops on all weeks in both years. It was revealed that P. persimilis markedly suppressed T. urticae on eggplant and tomato compared to pepper and cucumber in both years. It is clear that the host crops is a key factor on the success of P. persimilis on the biological control of T. urticae on field-grown vegetables. Consequently, it is thought that these results should be taken into account in the biological control strategies of mite pests by using the predatory mites on field-grown vegetables.

An overview of the biological ammonia treatment, model prediction and control strategies in water and wastewater treatment plant

Water disruption has always been a major issue in Malaysia. The reason for the frequent water disruption is due to the shutdown of water treatment plant (WTP) for unable to process contaminated raw water from the river. In wastewater treatment plant (WWTP), main source of ammonia is from the breakdown of proteins and amino acids in organic waste. Typically, ammonia is not fully removed from the WWTP and most of the ammonia is being discharged together with the plant effluent into the river streams. High levels of ammonia in the water exerts an oxygen demand which causes oxygen depletion. Hence, affecting the aquatic ecosystem and creates a toxic environment for the aquatic life. Biological treatment is known to be the most cost saving method as it only constructs of simple components, chemical free treatment and producing no harm by-products which later cause cost increment for additional treatment. Furthermore, biological treatment is capable in producing high quality treated drinking water that meets the standard water guidelines and regulations. In this paper, the aim is to conduct an overview on the application of biological treatment as an alternative treatment method of ammonia removal in water and wastewater treatment plant. This overview presents the cohesive approach of biological treatment in water and wastewater treatment plant, source of ammonia pollution, standard implies on ammonia concentration to control potential hazards, reported cases and recent pollution status of ammonia globally. In addition, the use of an artificial intelligence for model prediction and control strategies for water treatment have been included in this overview.