Biological Control Strategies Research Articles

Understanding complex spatial dynamics from mechanistic models through spatio‐temporal point processes

Landscape heterogeneity affects population dynamics, which determine species persistence, diversity and interactions. These relationships can be accurately represented by advanced spatially‐explicit models (SEMs) allowing for high levels of detail and precision. However, such approaches are characterised by high computational complexity, high amount of data and memory requirements and spatio‐temporal outputs may be difficult to analyse. A possibility to deal with this complexity is to aggregate outputs over time or space, but then interesting information may be masked and lost, such as local spatio‐temporal relationships or patterns. An alternative solution is given by meta‐models and meta‐analysis, where simplified mathematical relationships are used to structure and summarise the complex transformations from inputs to outputs. Here, we propose an original approach to analyse SEM outputs. By developing a meta‐modelling approach based on spatio‐temporal point processes (STPPs), we characterise spatio‐temporal population dynamics and landscape heterogeneity relationships in agricultural contexts. A landscape generator and a spatially‐explicit population model simulate hierarchically the pest–predator dynamics of codling moth and ground beetles in apple orchards over heterogeneous agricultural landscapes. Spatio‐temporally explicit outputs are simplified to marked point patterns of key events, such as local proliferation or introduction events. Then, we construct and estimate regression equations for multi‐type STPPs composed of event occurrence intensity and magnitudes. Results provide local insights into spatio‐temporal dynamics of pest–predator systems. We are able to differentiate the contributions of different driver categories (i.e. spatio‐temporal, spatial, population dynamics). We highlight changes in the effects on occurrence intensity and magnitude when considering drivers at global or local scale. This approach leads to novel findings in agroecology where, for example, we show that the organisation of cultivated patches and semi‐natural elements play different roles for pest regulation depending on the scale considered. It aids to formulate guidelines for biological control strategies at global and local scale.

Transmission-Blocking Strategies Against Malaria Parasites During Their Mosquito Stages.

Malaria is still the most widespread parasitic disease and causes the most infections globally. Owing to improvements in sanitary conditions and various intervention measures, including the use of antimalarial drugs, the malaria epidemic in many regions of the world has improved significantly in the past 10 years. However, people living in certain underdeveloped areas are still under threat. Even in some well-controlled areas, the decline in malaria infection rates has stagnated or the rates have rebounded because of the emergence and spread of drug-resistant malaria parasites. Thus, new malaria control methods must be developed. As the spread of the Plasmodium parasite is dependent on the part of its life cycle that occurs in mosquitoes, to eliminate the possibility of malaria infections, transmission-blocking strategies against the mosquito stage should be the first choice. In fact, after the gametocyte enters the mosquito body, it undergoes a series of transformation processes over a short period, thus providing numerous potential blocking targets. Many research groups have carried out studies based on targeting the blocking of transmission during the mosquito phase and have achieved excellent results. Meanwhile, the direct killing of mosquitoes could also significantly reduce the probability of malaria infections. Microorganisms that display complex interactions with Plasmodium, such as Wolbachia and gut flora, have shown observable transmission-blocking potential. These could be used as a biological control strategy and play an important part in blocking the transmission of malaria.

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

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

Impact of heavy metal exposure on biological control of a deadly amphibian pathogen by zooplankton

Despite devastating effects on global biodiversity, efficient mitigation strategies against amphibian chytridiomycosis are lacking. Since the free-living pathogenic zoospores of Batrachochytrium dendrobatidis (Bd), the infective stage of this disease, can serve as a nutritious food source for components of zooplankton communities, these groups may act as biological control agents by eliminating zoospores from the aquatic environment. Such pathogen-predator interaction is, however, embedded in the aquatic food web structure and is therefore affected by abiotic factors interfering with these networks. Heavy metals, released from both natural and anthropogenic sources, are widespread contaminants of aquatic ecosystems and may interfere with planktonic communities and thus pathogen elimination rates. We investigated the interaction between zooplankton communities and chytridiomycosis infections in a Flemish agricultural region. Moreover, we also investigated the impact of heavy metal contamination, that was previously investigated in the region and presented in recent work, on zooplankton assemblages and chytridiomycosis infections. Finally, we tested the effect of sublethal concentrations of copper and zinc on Bd removal rates by Daphnia magna in a laboratory assay. Although zinc, copper, nickel and chromium were widely abundant pollutants, heavy metals were no driving force for zooplankton assemblages at our study locations. Moreover, our field survey did not reveal indirect effects of zooplankton assemblages on chytridiomycosis infections. However, sampling occasions testing negative for Bd showed a higher degree of copper contamination compared to positive sampling occasions, indicating a potential inhibitory effect of copper on Bd prevalence. Finally, whereas D. magna significantly reduced zoospore densities in its environment, sublethal concentrations of copper and zinc showed no interference with pathogen removal in the laboratory assay. Our results provide perspectives for further research on such a biological control strategy against chytridiomycosis by optimizing environmental conditions for pathogen predation.

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

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

Half Friend, Half Enemy? Comparative Phytophagy between Two Dicyphini Species (Hemiptera: Miridae).

Simple SummaryOmnivorous predators, such as some mirids, are important biological control agents in several vegetable crops since they are generalists and can survive in the crop in the absence of prey. Nesidiocoris tenuis is a mirid used worldwide and its phytophagy is well known, which is not the case for the Palearctic Dicyphus cerastii. To use the latter in biological control it is crucial to evaluate the damage it causes to plants. We compared these two mirid species, under laboratory and semi-field conditions, regarding the damage they caused to plants and fruit, and their location on the plant versus on the fruit. Both species produced plant damage (scar punctures on leaves and necrotic patches on petioles) and caused flower abortion, at a similar level, however, only N. tenuis produced necrotic rings. Overall, N. tenuis females produced more damage to tomato fruit than D. cerastii. There was an increased frequency of D. cerastii females found on the plants over time, which did not happen with N. tenuis. Our results suggested that although D. cerastii caused less damage to tomato fruit than N. tenuis, it did feed on the fruit and could cause floral abortion, which requires field evaluation and caution in its use.Despite their importance as biological control agents, zoophytophagous dicyphine mirids can produce economically important damage. We evaluated the phytophagy and potential impact on tomato plants of Dicyphus cerastii and Nesidiocoris tenuis. We developed a study in three parts: (i) a semi-field trial to characterize the type of plant damage produced by these species on caged tomato plants; (ii) a laboratory experiment to assess the effect of fruit ripeness, mirid age, and prey availability on feeding injuries on fruit; and (iii) a laboratory assay to compare the position of both species on either fruit or plants, over time. Both species produced plant damage, however, although both species produced scar punctures on leaves and necrotic patches on petioles, only N. tenuis produced necrotic rings. Both species caused flower abortion at a similar level. Overall, N. tenuis females produced more damage to tomato fruit than D. cerastii. There was an increased frequency of D. cerastii females found on the plants over time, which did not happen with N. tenuis. Our results suggested that, although D. cerastii caused less damage to fruit than N. tenuis, it still fed on them and could cause floral abortion, which requires field evaluation and caution in its use in biological control strategies.

First record of miracine parasitoid wasps (Hymenoptera: Braconidae) from Australia: molecular phylogenetics and morphology reveal multiple new species

AbstractMiracinae are a small subfamily of parasitoid wasps that are under‐represented in collections and that have yet to be formally recorded from Australia. Bayesian and maximum likelihood phylogenetic analyses were performed using the barcoding region of cytochrome c oxidase subunit I (COI) from 11 miracine specimens collected throughout Australia, along with extralimital miracine COI sequences from the Barcode of Life Database (BOLD). Of 14 miracine sequences from Australia, 11 distinct species were identified at a 2% pairwise difference threshold. Four of these species, for which female specimens were available for morphological examination, are here described: Mirax arcisensis Slater‐Baker & Fagan‐Jeffries sp. nov., Mirax caelicus Slater‐Baker & Fagan‐Jeffries sp. nov., Mirax cowellensis Slater‐Baker & Fagan‐Jeffries sp. nov. and Mirax trianguliceps Slater‐Baker & Fagan‐Jeffries sp. nov. Although specimens are apparently rare in collections, these results suggest that the continent may have a much larger endemic miracine fauna and highlights the need for additional work on the subfamily in Australia. Further studies on the taxonomy and biology of Australian miracines could have important implications for conservation and may reveal opportunities for biological control strategies against leaf‐mining pests.

Detection of Wolbachia and Leishmania DNA in sand flies (Diptera: Psychodidae, Phlebotominae) from a focus of cutaneous leishmaniasis in Tabasco, Mexico.

Phlebotomine sand flies are the main vectors of Leishmania genus species worldwide; therefore, the detection of some reproductive parasites, such as Wolbachia, has been considered a possible strategy for biological control. In Mexico, leishmaniasis cases have been recorded in 25 states, yet only two sand fly species have been related to Wolbachia spp. Although the state of Tabasco has a high number of leishmaniasis cases, only few studies have been done on sand fly species. The aim of this study was to analyze the diversity of sand fly species and to detect Wolbachia spp. and/or Leishmania spp. in the captured specimens. Sand flies were collected at the locality of Huimango, Tabasco, Mexico, during October 2019, using nine light traps (CDC) and two Shannon traps per night. The specimens were identified and females were analyzed by PCR for the DNA detection for pathogens. A total of 193 sand fly specimens belonging to five species were morphologically identified. Pintomyia ovallesi was the most abundant species (76.84%), followed by Micropygomyia cayennensis (6.40%). Furthermore, first records of four sand fly species were established for the state of Tabasco, thereby increasing the species richness in the state from four to eight. We observed a natural infection rate of 9.7% (10/103) for Leishmania and 0.91% (1/103) for Wolbachia. The importance of conducting entomological surveys in endemic areas of leishmaniasis in Mexico is highlighted, to determine whether other sand fly species may be potential vectors of Leishmania spp., and if some Wolbachia strains could be relevant for the control of leishmaniasis.

Composition identification and functional verification of bacterial community in disease-suppressive soils by machine learning.

It has been widely reported that probiotic consortia in the rhizosphere can enhance the plant resistance to pathogens. However, the general composition and functional profiles of bacterial community in soils which suppress multiple diseases for various plants remain largely unknown. Here, we combined metadata analysis with machine learning to identify the general patterns of bacterial-community composition in disease-suppressive soils. Disease-suppressive soils significantly enriched Firmicutes and Actinobacteria but showed a decrease in Proteobacteria and Bacteroidetes. Our machine-learning models accurately identified the disease-conducive and -suppressive soils with 54 biomarker genera, 28 of which were potentially beneficial. We further carried out a successive passaging experiment with the susceptible rps2 mutant of Arabidopsis thaliana invaded by Pseudomonas syringae pv. tomato DC3000 (avrRpt2) for functional verification of potential beneficial bacteria. The disease-suppressive ability of Kribbella, Nocardioides and Bacillus was confirmed, and they positively activated the pathogen-associated molecular patterns-triggered immunity pathway. Results also showed that chemical control by pesticides in agricultural production decreased the disease-suppressive ability of soil. This study provides a method for accurately predicting the occurrence of multiple diseases in soil and identified potential beneficial bacteria to guide a wide range of multiple-strain biological control strategies in agricultural management.

Lantana camara: Poisonous Species and a Potential Browse Species for Goats in Southern Africa—A Review

Among the possible impacts of plant invaders on South African biodiversity, water supplies, and rangeland production, Lantana camara is ranked the highest in terms of its environmental impact. Globally, L. camara is regarded as one of the most ecologically and economically destructive invasive alien plants. The spread of L. camara affects the environment and threatens livestock productivity due to its toxicity to animals (especial cattle and sheep) in most semi-arid areas of South Africa. Lantana camara is known to have high concentrations of nutrients that are beneficial to livestock, but most previous research has concentrated on its toxicity. To enrich our knowledge on its nutritive value, further research has to evaluate its dietary impact on the growth and health of different ruminant livestock species, particularly goats. This review evaluates L. camara as a potential browse species for goats in southern Africa, and its adverse effects on goats and other ruminant livestock are also presented. The review describes L. camara and its distribution globally, its poisonous effect to livestock, and potential use as an alternative forage to browsing animals such as goats, which have proved resistant to its harmful traits. The high crude protein content, low fibre and adequate macro-minerals for small ruminants makes L. camara a good ruminant protein supplement in semi-arid areas. In addition to other biological control strategies, the prospects of using goats as a biological management tool is discussed. The research will contribute to the understanding of the control measures of L. camara while improving the productivity of small stock, especially goats. This means that a balanced understanding of its nutritional value as a source of protein and its negative impact on the environment should be considered in developing mitigation strategies to arrest its spread. We, therefore, recommend the use of goats in the control of L. camara; however, further studies are needed to limit its toxic effects, and thus improve its value.

Root-knot nematodes (Meloidogyne spp.) a threat to agriculture in Mexico: biology, current control strategies, and perspectives.

Root-knot nematodes (RKN) are sedentary parasites of the roots of plants and are considered some of the most damaging pests in agriculture. Since RKN target the root vascular system, they provoke host nutrient deprivation and defective water transport, causing above-ground symptoms of growth stunting, wilting, chlorosis, and reduced crop yields. In Mexico RKN infestations are primarily dealt with by treating with synthetic chemically based nematicides that are preferred by farmers over available bioproducts. However, due to environmental and human health concerns chemical control is increasingly restricted. Biological control of RKNs can help reduce the use of chemical nematicides as it is achieved with antagonistic organisms, mainly bacteria, fungi, other nematodes, or consortia of diverse microorganisms, which control nematodes directly by predation and parasitism at different stages: eggs, juveniles, or adults; or indirectly by the action of toxic diffusible inhibitory metabolites. The need to increase agricultural production and reduce negative environmental impact creates an opportunity for optimizing biological control agents to suppress nematode populations, but this endeavour remains challenging as researchers around the world try to understand diverse control mechanisms, nematode and microbe life cycles, ecology, metabolite production, predatory behaviours, molecular and biochemical interactions, in order to generate attractive products with the approval of local regulatory bodies. Here, we provide a brief review of the biology of the genus Meloidogyne, biological control strategies, and a comparison between chemical and bioproducts in the Mexican market, and guidelines emitted by national agencies to ensure safety and effectiveness of new developments.

Complete genome sequence of Bacillus thuringiensis BR145, a strain with insecticidal activity against Lepidoptera pests.

Bacillus thuringiensis BR145 isolated from a soybean field in Southern Brazil showed toxicity against two important insect pests from soybean crop, Helicoverpa armigera, and Chrysodeixis includens, with LC50 0.294 µg.cm-2 and 0.277 µg.cm-2, respectively. We analyzed the genome of this strain through sequences obtained by Next Generation DNA Sequencing and de novo assembly. The analysis of the genome revealed insecticidal genes cry1Aa, cry1Ab, cry1Ac, cry1Ia, cry2Ab, cyt1, and vip3Aa, suggesting the use of this strain in new strategies of biological control.

Abundance and diversity of insect pests and their natural enemies in Brassica campestris (L.) crop ecosystem

For the development of an efficient ecological and biological control strategy that are economically and environmentally sound, it is essential to study the diversity indexes and abundance of insect fauna. In this study we recorded a total number of twelve species of insect pests and twenty four species of natural enemies throughout the cropping season of Brassica campestries during 2019–20 and 2020–21. Among insect pests mustard aphid species (Lipaphis erysimi pseudobrassicae, Myzus persicae) were dominant in both the years with relative abundance of 73.46 and 76.70% respectively. Amongst natural enemies Coccinella septempunctata (14.66 and 16.36%) and Diaeretiella rapae (21.97 and 17.89%) were dominant in both the years respectively. The diversity indexes of insect pests and natural enemies with respect to the Shannon index (H = 0.78, 1.54), Richness (M.I. = 6.34, 7.18), Evenness (J = 0.23, 0.45) was higher during 2020–2021 respectively. This study offer some new insights into the frequency of insect pests and their natural enemies, and may support the idea that sustaining ecosystem health and fostering biodiversity may require an ecological and biological approach to pest management.

The inhibitory action of plant extracts on the mycelial growth of Ascosphaera apis, the causative agent of chalkbrood disease in Honey bee

Ascosphaera apis is a fungal pathogen, which causes chalkbrood disease in bees and is threatening beekeeping worldwide. The demand for organic honey for export has lately heightened hence the biological control is the option. This study aimed at the in vitro evaluation of the potency of plant extracts against chalkbrood disease for the possibility of being employed as a biological control strategy. The results showed that the combination of plant extracts from cinnamon with spearmint, cinnamon with lemongrass, cinnamon with geranium, and cinnamon with palmarosa at a concentration of 25% and 12.5% inhibited mycelial growth of A. apis by 100%. This demonstrated the potentiality of combining different plant extracts in controlling this disease. In addition, oregano caused inhibition of up to 100% singly. Conclusively, cinnamon in combination with several extracts has a great potential in curbing this disease while oregano offers an amazing remedy and hence the best formulations should be generated for the beekeeper to utilize.

Evaluation of strategies of pesticide use and biological control through linear feedback control for controlling rapidly growing pest population

Evaluation of strategies of pesticide use and biological control through linear feedback control for controlling rapidly growing pest population

Predstavnici roda "Trissolcus" (Hymenoptera: Scelionidae) prirodni neprijatelji štetnih stenica (Hemiptera: Pentatomidae) i preliminarna istraživanja u Srbiji

Different types of polyphagous true bug pests are present in Serbia and countries in the region, many of which stand out as significant pests of agricultural crops. Among the harmful true bugs, the green vegetable bug, Nezara viridula Linnaeus, 1758 and the brown marble bug Halyomorpha halys Stål, 1855 (Hemiptera: Pentatomidae) are the species that currently attract attention the most, primarily because of their invasive and polyphagous nautre and ability to migrate rapidly from one crop to another. In many regions, where harmful bugs cause large economic losses, control strategies are primarily based on the application of chemicals. In addition to chemical control measures, biological control measures are increasingly present, which are based on the application of natural enemies of pests. Species from the genus Trissolcus (Hymenoptera: Scelionidae) show the best results in the biological control of polyphagous true bug. The species that has been commercially used for many years to control harmful Hemiptera is Trissolcus basalis Wollaston, 1958, which is one of the most important natural enemies of the green vegetable bug in the World. The species Trissolcus japonicus Ashmead, 1904 and Trissolcus mitsukurii Ashmead, 1904 have been identified as the predominant parasitoids of the brown marble bug and show great potential in the biological control of this harmful species. Representatives of the genus Trissolcus are also registered on the territory of Serbia, which opens the possibility of including native species of the genus Trissolcus in the strategies of biological control of true bug pests on the territory of Serbia and the region.

Evaluation of Cuban Bacillus thuringiensis (Berliner, 1911) (Bacillales: Bacillacea) isolates with larvicidal activity against Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae)

Objective: To evaluate 11 Cuban native Bacillus (B.) thuringiensis isolates in order to select one with the best larvicidal activity against Aedes (Ae.) aegypti and low cytotoxicity.Methods: The cry and cyt genes of the isolates (A21, A51, L95, L910, M29, R84, R85, R87, R89, U81 and X48) were amplified by PCR. The influence of organic matter and NaCl on the larvicidal activity was tested by bioassays. Cytotoxicity was assayed on peritoneal macrophages of BALB/c mice.Results: The cyt1 (Aa, Ab, Ba), cyt2, cry4aA, cry4Ba, cry11 (Aa, Ba, Bb) and cry10 genes were identified in all native Cuban isolates. The larvicidal activity (LC90) of seven isolates was affected by the presence of organic matter in the water, while A21, A51, L910, R84, U81 and X48 had better LC50, LC90, LC95 than the 266/2 9-VII-98 control strain. The LC50 of two isolates was affected by the presence of NaCl and A21, A51, R85 isolate had better larvicidal activity than the 266/2 9-VII-98 control strain. In terms of toxicity against macrophages, the extracts of nine isolates were less cytotoxic than the control strains.Conclusions: Native isolate A21 had the main virulence factors against Ae. aegypti larvae, displayed a good larvicidal activity in presence of different factors related with Ae. aegypti breeding sites, and had low citotoxicity against macrophages. These results can contribute to the improvement of existing biological control strategies and the development of new biolarvicides.

Mathematical modeling and analysis of biological control strategy of aphid population

<abstract><p>To study the biological control strategy of aphids, in this paper we propose host-parasitoid-predator models for the interactions among aphids, parasitic wasps and aphidophagous Coccinellids incorporating impulsive releases of Coccinellids, and then study the long-term control and limited time optimal control of aphids by adjusting release amount and release timing of Coccinellids. For the long-term control, the existence and stability of the aphid-eradication periodic solution are investigated and threshold conditions about the release amount and release period to ensure the ultimate extinction of the aphid population are obtained. For the limited-time control, three different optimal impulsive control problems are studied. A time rescaling technique and an optimization algorithm based on gradient are applied, and the optimal release amounts and timings of natural enemies are gained. Our simulations indicate that in the limited-time control, the optimal selection of release timing should be given higher priority compared with the release amount.</p></abstract>

Genomic Analysis of the First European Bacteriophages with Depolymerase Activity and Biocontrol Efficacy against the Phytopathogen Ralstonia solanacearum.

Ralstonia solanacearum is the causative agent of bacterial wilt, one of the most destructive plant diseases. While chemical control has an environmental impact, biological control strategies can allow sustainable agrosystems. Three lytic bacteriophages (phages) of R. solanacearum with biocontrol capacity in environmental water and plants were isolated from river water in Europe but not fully analysed, their genomic characterization being fundamental to understand their biology. In this work, the phage genomes were sequenced and subjected to bioinformatic analysis. The morphology was also observed by electron microscopy. Phylogenetic analyses were performed with a selection of phages able to infect R. solanacearum and the closely related phytopathogenic species R. pseudosolanacearum. The results indicated that the genomes of vRsoP-WF2, vRsoP-WM2 and vRsoP-WR2 range from 40,688 to 41,158 bp with almost 59% GC-contents, 52 ORFs in vRsoP-WF2 and vRsoP-WM2, and 53 in vRsoP-WR2 but, with only 22 or 23 predicted proteins with functional homologs in databases. Among them, two lysins and one exopolysaccharide (EPS) depolymerase, this type of depolymerase being identified in R. solanacearum phages for the first time. These three European phages belong to the same novel species within the Gyeongsanvirus, Autographiviridae family (formerly Podoviridae). These genomic data will contribute to a better understanding of the abilities of these phages to damage host cells and, consequently, to an improvement in the biological control of R. solanacearum.

Incidence of Groundnut Leafminer (GLM), Aproaerema modicella (Deventer) (Lepidoptera: Gelechiidae) and its Parasitic Fauna on Alternate Leguminous Hosts in Tamil Nadu, India

Background: The groundnut leafminer (GLM), Aproaerema modicella is an important pest of several legume crops which causes 50 to 100 per cent yield loss in India. The exploration of indigenous natural enemies is crucial to the success of every biological control strategy. Besides, alternative host plants act as a source of both herbivorous pests and their natural enemies. In this view, occurrence of GLM and their parasitic fauna on groundnut, alternate leguminous hosts viz., redgram and babchi were recorded. Methods: Survey on damage potential of GLM and their parasitic fauna were recorded on groundnut at Sivagangai and Coimbatore districts of Tamil Nadu, India during 2016 to 2018. Survey was also conducted to find the damage potential of A. modicella on alternate leguminous hosts viz., redgram, babchi and their parasitic fauna at Coimbatore district. The damage potential of A. modicella, per cent parasitization and parasitoid emergence were assessed from A. modicella infested groundnut, redgram and babchi leaves. Result: Severe incidence of A. modicella was recorded as 98.10% (2016 to 2017) and 98.45% (2017 to 2018) at Sivagangai district. The parasitization of GLM was also found higher at Sivagangai recording 46.67% in both the years which was positively related with the pest population. 13 hymenopteran parasitoids belonging to eight families were recorded. Among them, Avga choaspes Nixon recorded high per cent parasitoid emergence (20.00%). Furthermore, GLM incidence on redgram and babchi indicated the highest damage potential of 38.20 and 34.50 per cent and parasitization of 33.33 and 20.00 per cent, respectively during 2017 to 2018.