Introduction Of Natural Enemies Research Articles

Survey on Aculops lycopersici and operational factors potentially affecting successful pest management among 50 tomato producers in Germany

Aculops lycopersici (Acari: Eriophyoidea) is a pest in tomato cultivation worldwide. In recent years, the number of reports of A. lycopersici infestations in tomato have increased in Germany. In the first half of 2019, a survey of 50 tomato producing farms was conducted to assess the occurrence of A. lycopersici and the impact this pest has on tomato cultivation in Germany. The participating farms represented ~ 3.5% of the 1448 farms in Germany with protected tomato production in 2019. Total tomato production area considered in the survey was 131.8 ha which corresponds to ~ 34% of the 385.63 ha of protected tomato production area in Germany in this year. A. lycopersici presence was reported by 33 of the 50 surveyed farms, within the last 5 years. Amongst these 50 participants it was the pest with the highest relative importance in terms of plant protection effort exerted. A. lycopersici occurrence was reported more frequently from production systems with a higher intensification. For instance, heating in cold months and a larger production area were considered intensification factors in this study. However, due to autocorrelation between intensification factors it was not possible to link increased occurrence to specific factors. As the intensification factors favouring A. lycopersici occurrence are more prevalent in integrated production, those farms faced A. lycopersici occurrence more often than the organic growers in this study. Plant protection strategies often combine broad treatments of sulphur with local abamectin treatments, removal of infested plant material and the introduction of natural enemies.

Validation of Integrated Pest Management Modules against Piercing and Sucking Insect Pest of Rice

Background: Rice is one of the most common cereal crops in India, which has been found attacked by several insect pests including hoppers, stem borer, leaf folder, gall midge and ear head bugs. Farmers typically employ insecticides as preventative and curative management which causes needless issues. Although integrated pest management (IPM) has been recommended to nullify the ill effects of chemicals pesticides, farmers are hesitant to employ the IPM’s components and mostly rely on pesticides. IPM integrates knowledge-based techniques of biological, cultural, physical, host plant resistance and chemical control strategies in order to limit pest populations considered economically acceptable. Present investigation was conducted to evaluate the effectiveness of IPM strategy improving upon the crop productivity. Methods: An Integrated Pest Management (IPM) module comprising of spacing, introduction of natural enemies, application of botanicals, entomopathogenic fungi, installation of yellow sticky traps and chemical pesticide (Thiamethoxam) was assessed in comparison with Farmers Practice (FP) (usual routine followed by the farmer during the cropping season) in the farmer’s fields. Result: The pooled mean data of per cent leaf incidence by Nephotettix virescens ranged between 4.59-6.25% during the two years research in IPM module, while in farmers practices mean leaf damage varied between 8.09-8.61%. Similarly, the leaf damage caused by Nilaparvata lugens ranged between 4.88-7.61% as compared to 8.64-10% in the farmers practices. The BC ration was recorded to be 1: 7.6 and 1:6.85 during 2018 and 2019, respectively.

Does the fundamental host range of Trissolcus japonicus match its realized host range in Europe?

Unintentional introduction of natural enemies has increased in recent years due to a massive rise in global trade and tourism. One such natural enemy is the Asian egg parasitoid Trissolcus japonicus, a promising agent for classical biological control of Halyomorpha halys. In Europe, adventive T. japonicus populations have been detected in Switzerland, Italy and Germany. Host specificity testing demonstrated that its fundamental host range is fairly broad; however, it is unclear whether spatial or temporal refuges reduce parasitism of non-target species in the field. To address this, the realized host range of T. japonicus was assessed over three years by exposing sentinel egg masses of H. halys and 18 non-target species and collecting naturally laid egg masses in Switzerland and Italy. In total, 15 of 18 non-target species were successfully parasitized by T. japonicus in the field, confirming its broad fundamental host range. However, most non-target species were less parasitized by T. japonicus than H. halys, profiting from either partial temporal or spatial refuges from parasitism. Species with an unusual life cycle and the same ecological niche as H. halys, such as Pentatoma rufipes, which was the most parasitized non-target species in both countries, potentially face an increased risk of parasitism. In contrast, beneficial non-target effects may occur for the invasive pest, Nezara viridula, which suffered high non-reproductive mortality induced by T. japonicus. In both cases, life table studies will be needed to determine the impact of non-target parasitism and the potential consequences at the population level.

Principles and strategies of biological control economically harmful forest organisms

Essentially, biological control is nothing but applied ecology, ie the use of natural enemies to (regulatory) reduce abundance in pest populations. Intellectually satisfying, biologically intriguing and ecologically rational, a means of pest control, biological control, is one of the areas of integrated management and protection of forest ecosystems, which is rapidly developing and brings together scientists from many disciplines. Ecologists, entomologists, pathologists of plants and insects, microbiologists, approach the subject of research from different angles. Each discipline uses biological control in order to reduce the number of pests or pathogens, through the activity of beneficial living organisms. Biological control of economically harmful forest organisms means that those who decide on its application in specific environmental conditions should first accurately identify the type of pest, assess the level of infestation and predict potential economic damage, explore all available strategies, their advantages and disadvantages, and select the most efficient, which must be in correlation with all applicable local, national and international regulations. Within the biological control of pests, mainly insects, various strategies are used, which basically include the introduction of natural enemies, predators, parasitoids and pathogens, indigenous and allochthonous harmful insect species (classical and inoculation biological control) and increasing their numbers (inundative biological suppression). It should be noted here that the legislation in the field of nature and environmental protection prohibits the introduction of allochthonous, exotic species into natural and anthropogenic ecosystems in many countries, and therefore, the application of biological control is quite limited. A special, promising, strategy within biological control is the selection of strains with genetically induced ability of autocidal action. Entomopathogenic organisms, various types of viruses, microsporidia, bacteria, protozoa, fungi, which under favorable conditions can cause mass death of insects, live normally in nature and are important regulatory factors in host populations. Epizootics caused by natural viral and fungal pathogens are often responsible for spectacular crashes in populations of graded species, e.g. gubara, žutotrbe, ordinary and red pine sol. Despite such brilliant characteristics, a small number of them are included in certain biological control strategies. Suppression of plant pathogens can rarely be achieved without a careful combination of many techniques. Legislation in the field of nature and environmental protection in many countries prohibits the introduction of non-native, exotic species, and thus, the application of a number of biological control strategies is prevented.The application of fungicides in forest ecosystems is usually too expensive, so biological control measures are preferred, through the use of antagonistic or hypovirulent species of microorganisms and their strains. In essence, when it comes to plant pathogens, biological control measures are more preventive than palliative or curative, and are based on sustainable ecological concepts of forest ecosystems.

Prospects for classical biological control of Spodoptera frugiperda (Lepidoptera: Noctuidae) in invaded areas using parasitoids from the Americas.

Fall armyworm, Spodoptera frugiperda (J.E. Smith) is a polyphagous agricultural pest threatening food security worldwide. This American species recently invaded most of Africa, many Asian countries, and Oceania, where it mainly damages maize. Classical biological control (CBC) through the introduction of natural enemies from its area of origin is considered as a potential management approach. The paper reviews the prospects and constraints of a CBC programme against S. frugiperda using larval parasitoids, which are considered the most suitable natural enemies for introduction against this pest. The most important larval parasitoids in its native range are presented and discussed for their suitability as CBC agents, based the following criteria: their frequency of occurrence and parasitism levels, specificity, climatic suitability and absence of closely related species parasitizing S. frugiperda in the area of introduction. The ichneumonid Eiphosoma laphygmae Costa-Lima (Hymenoptera: Icheumonidae) is considered as a potential candidate for introduction because of its specificity and its importance as a parasitoid of the pest in most of its native range. The most frequent and important parasitoid of S. frugiperda in the Americas, the braconid Chelonus insularis Cresson (Hymenoptera: Braconidae), would most probably contribute to the control of S. frugiperda if released in invaded areas. However, it is oligophagous and would most certainly parasitize nontarget species. Before introducing C. insularis, or any other parasitoid species, the potential nontarget effects will have to be assessed and the risks will have to be weighed against the benefits of improving the natural control of this important pest.

Risk Analysis Frameworks Used in Biological Control and Introduction of a Novel Bayesian Network Tool.

Classical biological control, the introduction of natural enemies to new environments to control unwanted pests or weeds, is, despite numerous successful examples, associated with rising concerns about unwanted environmental impacts such as population decline of nontarget species. Recognition of these biosafety risks is globally increasing, and prerelease assessments of biological control agents (BCAs) have become more rigorous in many countries. We review the current approaches to risk assessment for BCAs as used in Australasia, Europe, and North America. Traditionally, these assessments focus on providing assurance about the specificity of a proposed BCA, generally via a list of suitable versus nonsuitable hosts determined through laboratory specificity tests (i.e., by determining the BCA's physiological host range). The outcome of interactions of proposed agents in the natural environment can differ from laboratory-based predictions. Potential nontarget host testing may be incomplete, additional ecological barriers under field conditions may limit encounters between BCA and nontargets or reduce attack levels, and BCAs could disperse to habitats beyond those used by the target species and adversely affect nontarget species. We advocate for the adoption of more comprehensive, ecologically-based, probabilistic risk assessment approaches to BCA introductions. An example is provided using a Bayesian network that can integrate information on probabilities and uncertainties of a BCA to spread and establish in new habitats, interact with nontarget species in these habitats, and eventually negatively impact the populations of these nontarget species. Our new model, Biocontrol Adverse Impact Probability Assessment, aims to be incorporated into a structured decision-making framework to support national regulatory authorities.

Niche Modeling May Explain the Historical Population Failure of Phytoseiulus persimilis in Taiwan: Implications of Biocontrol Strategies.

Simple SummaryPhytoseiulus persimilis Athias-Henriot, a mite species widely used in pest management for the control of spider mites, has been commercialized and introduced to numerous countries. In the 1990s, P. persimilis was imported to Taiwan, and a million individuals were released into the field. However, none have been observed since then. In this study, we explored the ecological niche of this species to determine reasons underlying its establishment failure. The results indicate that P. persimilis was released in areas poorly suited to their survival. To the best of our knowledge, the present study is the first to predict the potential distribution of phytoseiids as exotic natural enemies. This process should precede the commercialization of exotic natural enemies and their introduction into any country.Biological control commonly involves the commercialization and introduction of natural enemies. Phytoseiulus persimilis Athias-Henriot, a mite species widely used in the control of spider mites, was imported to Taiwan in the 1990s and was mass-reared and released into the field. However, none have been observed in comprehensive surveys of phytoseiid mites for over 30 years. In this study, the distribution of P. persimilis in Taiwan was predicted, and environmental variables that affect its distribution were analyzed. The mountainous region of southcentral Taiwan was determined to be suitable for the establishment of this species, whereas the four sites at which it was released in the 1990s, particularly those in southwestern Taiwan, exhibited low suitability. Notably, the minimum temperature of the coldest month was identified as a crucial limiting factor affecting the distribution of P. persimilis, indicating that a Mediterranean climate is more suitable for this species. To the best of our knowledge, this study is the first to predict the suitable distribution of exotic predatory mites in a biological control program. The present findings serve as a pivotal assessment framework for the commercialization and foreign introduction of natural enemies.

Biological control of thrips pests (Thysanoptera: Thripidae) under greenhouse conditions in Transylvania, Romania

In present, vegetable cultivation faces significant challenges for two reasons: (i) cultivators have to produce healthy, first-class goods, and (ii) vegetables are allowed to contain only a specified pesticide residue. Development of insecticide resistance as a result of repeated insecticide treatments is causing difficulties to cultivators, who have paid attention to biological control methods over recent years. In Romania, pepper sprouting represents a prominent place in greenhouse vegetable production. Under greenhouse conditions, one of the most dangerous pests of peppers is the western flower thrips (Frankliniella occidentalis), which can trigger high economic losses. In recent years, several populations have been found resistant to insecticides and other active compounds, therefore, in our experiments, performed under greenhouse conditions, we used the predatory mite Amblyseius swirskii and the pirate bug Orius laevigatus against the western flower thrips. In addition to thrips, we monitored the growth and spread of introduced beneficial organisms based on collected flower samples. We also evaluated the relationships between beneficial organisms and greenhouse climate data. Introduction of natural enemies has proven a success of biological plant protection, as thrips did not cause economic losses in our experiment.

A Mathematical Model for the Eradication of Anopheles Mosquito and Elimination of Malaria

A mathematical model to eliminate malaria by breaking the life cycle of anopheles mosquito using copepods at larva stage and tadpoles at pupa stage was derived aimed at eradicating anopheles pupa mosquito by introduction of natural enemies “copepods and tadpoles” (an organism that eats up mosquito at larva and pupa stage respectively). The model equations were derived using the model parameters and variables. The stability analysis of the free equilibrium states was analyzed using equilibrium points of Beltrami and Diekmann’s conditions for stability analysis of steady state. We observed that the model free equilibrium state is stable which implies that the equilibrium point or steady state is stable and the stability of the model means, there will not be anopheles adult mosquito in our society for malaria transmission. The ideas of Beltrami’s and Diekmann conditions revealed that the determinant and trace of the Jacobian matrix were greater than zero and less than zero respectively implying that the model disease free equilibrium state is stable. Hence, the number of larva that transforms to pupa is almost zero while the pupa that develop to adult is zero meaning the life-cycle is broken at the larva and pupa stages with the introduction of natural enemy. Maple was used for the symbolic and numerical solutions.

Compatibility of early natural enemy introductions in commercial pepper and tomato greenhouses with repeated pesticide applications.

Successful integrated pest management in protected crops implies an evaluation of the compatibility of pesticides and natural enemies (NE), as control strategies that only rely on one tactic can fail when pest populations exceed NE activity or pests become resistant to pesticides. Nowadays in Almería (Spain), growers release NE prior to transplanting or early in the crop cycle to favor their settlement before pest arrival because this improves biocontrol efficacy, although it extends pesticide exposure periods. The purpose of this research was to evaluate the compatibility of two applications of pesticides with key NE in 2‐year trials inside tomato and sweet pepper commercial greenhouses: Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), Orius laevigatus (Say) (Hemiptera: Anthocoridae) and Amblyseius swirskii (Athias‐Henriot) (Acari: Phytoseiidae). In tomato, flubendiamide and chlorantraniliprole (IOBC category 1) were compatible with N. tenuis, but chlorpyrifos‐methyl and spinosad (IOBC categories 2–3), which effectively reduced Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) density, compromised its predatory activity. In sweet pepper, chlorantraniliprole (IOBC category 1) was the only pesticide compatible with O. laevigatus while chlorantraniliprole, emamectin benzoate, spirotetramat and pymetrozine were harmless (IOBC category 1) to Amblyseius swirskii, and sulfoxaflor slightly harmful (IOBC category 2) to this phytoseiid predator.

Pengendalian hama padi secara terpadu di Desa Pulau Rambai Kabupaten Kampar

Komoditas padi merupakan pangan utama dan banyak ditanam di Desa Pulau Rambai Kecamatan Kampa Kabupaten Kampar. Serangan hama merupakan kendala utama dalam pembudidayaan tanaman padi. Konsep Pengendalian Hama Terpadu (PHT) diterapkan ke petani padi yaitu memadukan teknik pengendalian hama yang kompatibel, mengutamakan pengendalian alami menggunakan musuh alami. Pengabdian bertujuan memberikan penyuluhan, pendampingan dan bimbingan petani padi menerapkan PHT untuk meningkatkan kuantitas dan kualitas produksi padi. Sasaran yang ditujukan adalah petani padi di Desa Pulau Rambai. Metoda penerapan yang dilakukan adalah penyuluhan, pembimbingan dan pendampingan. Penyuluhan berupa penyajian di pondok sawah petani mengenalkan konsep PHT, pengelolaan budidaya tanaman yang kurang sesuai untuk perkembangan hama padi, dan pengenalan jenis musuh alami hama, dan jenis pengendalian yang ramah lingkungan seperti pestisida nabati dan agen hayati. Pembimbingan dan pendampingan petani dalam pemantauan hama, musuh alami, dan ekosistem padi. Tingkat ketercapaian sasaran program terpantau dari kuisioner yang diisi oleh petani sebelum penyuluhan dan akhir program kegiatan pendampingan. Dari kuisioner terlihat adanya perubahan pandangan dan pengetahuan petani dalam konsep pengendalian hama. Ketercapaian program juga terlihat dari adanya perubahan cara budidaya seperti sistem legowo 4x1 dengan 3 bibit per rumpun dan pengendalian hama menggunakan pestisida hayati sesuai yang disuluhkan.

Trapping success and flight behavior of two parasitoid species of the woodwasp Sirex noctilio

Classical biological control relies on the deliberate introduction of natural enemies to reduce pest populations below damage thresholds. Knowledge on key aspects of the behavior of antagonists and their population densities through time can be important to increase the efficiency of control programs. The woodwasp Sirex noctilio is a global threat to pine forests and biological control can be based, among other agents on two parasitoids, Ibalia leucospoides and Megarhyssa nortoni, with variable success. Currently no sensitive and standardized monitoring method exists for these control agents and little is known on their behavior, such as their vertical flight-distribution. Our aims were: firstly, assess the efficiency in capturing the parasitoids of four methods (two passive traps based on flight-path interception or caging previously-attacked trees to retain emerging insects, and two active traps baited with pine volatiles), and secondly establish the parasitoids vertical flight distribution. Ibalia leucospoides (females) was captured by all methods but intercept panel traps registered the highest captured individuals when accounting for effort. Conversely M. nortoni did not respond to baited traps, and low numbers were recorded in passive traps. Males of both species flew higher than females of I. leucospoides. Intercept traps baited with pine volatiles could be used to monitor I. leucospoides, but M. nortoni is not captured in these traps. We suggest that both species could be monitored by passively trapping insects at the moment of emergence from previously-infested trees. Further research is needed, especially on the chemical ecology of both species, to further develop inexpensive and standardized monitoring methods.

An early suitability assessment of two exotic Ophraella species (Coleoptera: Chrysomelidae) for biological control of invasive ragweed in Europe

Classical biological control is an important means of managing the increasing threat of invasive plants. It constitutes the introduction of natural enemies from the native range of the target plant into the invaded area. This method may be the only cost-effective solution to control the rapidly expanding common ragweed, Ambrosia artemisiifolia, in non-crop habitats in Europe. Therefore, candidate biocontrol agents urgently need to be assessed for their suitability for ragweed control in Europe. A previous literature review prioritized the host-specific leaf beetle Ophraella slobodkini as a candidate agent for ragweed control in Europe, whereas it rejected its oligophagous congener O. communa. Meanwhile, O. communa was accidentally introduced and became established south of the European Alps, and we show here that it is expanding its European range. We then present a short version of the traditional pre-release risk-benefit assessment for these two candidate agents to facilitate fast decision-making about further research efforts. We selected two complementary tests that can be conducted relatively rapidly and inform about essential risks and benefits. We conducted a comparative no-choice juvenile performance assay using leaves of ragweed and sunflower, the most important non-target plant, in Petri dishes in climatic conditions similar to that in the current European range of O. communa. This informs on the fundamental host range and potential for increasing abundance on these host plants. The results confirm that O. slobodkini does not survive on, and is hence unlikely to cause severe damage to sunflower, while O. communa can survive but develops more slowly on sunflower than on ragweed. In parallel, our species distribution models predict no suitable area for the establishment of O. slobodkini in Europe, while O. communa is likely to expand its current range to include a maximum of 18% of the European ragweed distribution. Based on this early assessment, the prioritization and further assessment of O. slobodkini seem unwarranted whereas the results urgently advocate further risk-benefit analysis of O. communa. Having revealed that most of the European area colonized by ragweed is unlikely to be suitable for these species of Ophraella we suggest the use of such relatively short and cheap preliminary assessment to prioritise other candidate agents or strains for these areas.

Augmentative biocontrol when natural enemies are subject to Allee effects.

Intraspecific interactions such as Allee effects are key properties that can guide population management. This contribution considers component Allee effects that are elementary mechanisms leading to declines of fitness at the population scale, i.e. demographic Allee effects. It especially focuses on the consequences of such properties in predator populations, and investigates their repercussions in a biological control context. A modelling framework able to account for reproductive and/or foraging component Allee effects is proposed. From this, four models of augmentative biological control, corresponding to the periodic introduction of natural enemies, have been investigated. This is done using semi-discrete models: ordinary differential equations are used to depict predator-prey dynamics and a discrete equation describes the abrupt augmentation of predators at periodic intervals. In that context, stability of a prey-free solution corresponding to pest eradication has been analyzed. It has been found that rare but large introductions should be preferred over frequent and small ones, when Allee effects influence predator populations. In particular, the occurrence of foraging, rather than reproducing, Allee effects significantly hinders pest eradication. Cases where the pest-free solution is locally, but not globally, stable were also observed and were shown to be favored by the occurrence of reproductive Allee effects among predators.

Oviposition Site Selection Structures Niche Partitioning Among Coccinellid Species in a Tropical Ecosystem.

The competitive exclusion hypothesis suggests that coexisting related species using similar resources in nature should partition their realized niches. This hypothesis has direct implications for conservation strategies using biological control, taking into consideration the shifts caused by the introduction of natural enemies in a local community. Such introductions typically lead to disruptions in species interactions and interfere with community structure. In this study, we asked whether community structure of aphidophagous lady beetles is determined by the distribution of specific plants and aphids. To answer this question, we describe the distribution patterns of lady beetles (adults, larvae, and egg clusters) relative to plants and aphids in eight crop ecosystems in a central region of Brazil. We used canonical correspondence analysis to evaluate lady beetle distribution relative to selected habitat variables. Cycloneda sanguinea L., Hippodamia convergens Guérin-Méneville, Harmonia axyridis Pallas, and Eriopis connexa Germar (Coleoptera: Coccinellidae) differed in their use of plants and aphids. The association of egg clusters with specific plants/aphids was stronger than that of larvae or adults. In conclusion, lady beetle species occupied different niches, indicating different patterns of habitat use that may facilitate their coexistence in crop ecosystems. Furthermore, immature individuals had more specific environmental associations than adults, likely because female choice of oviposition sites influences their distribution and thus lady beetle community structure.

Integrated Pest Management in a Predator-Prey System with Allee Effects.

A commonly used biocontrol strategy to control invasive pests with Allee effects consists of the deliberate introduction of natural enemies. To enhance the effectiveness of this strategy, several tactics of control of invasive species (e.g., mass-trapping, manual removal of individuals, and pesticide spraying) are combined so as to impair pest outbreaks. This combination of strategies to control pest species dynamics are usually named integrated pest management (IPM). In this work, we devise a predator-prey dynamical model in order to assess the influence of the intensity of chemical killing on the success of an IPM. The biological and mathematical framework presented in this study can also be analyzed in the light of species conservation and food web dynamics theory.

Guiding Classical Biological Control of an Invasive Mealybug Using Integrative Taxonomy.

Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is a mealybug of Southern African origin that has recently been introduced into Eastern Spain. It causes severe distortions on young citrus fruits and represents a growing threat to Mediterranean citrus production. So far, biological control has proven unsatisfactory due to the absence of efficient natural enemies in Spain. Hence, the management of this pest currently relies only on chemical control. The introduction of natural enemies of D. aberiae from the native area of the pest represents a sustainable and economically viable alternative to reduce the risks linked to pesticide applications. Since biological control of mealybugs has been traditionally challenged by taxonomic misidentification, an intensive survey of Delottococcus spp. and their associated parasitoids in South Africa was required as a first step towards a classical biological control programme. Combining morphological and molecular characterization (integrative taxonomy) a total of nine mealybug species were identified in this study, including three species of Delottococcus. Different populations of D. aberiae were found on wild olive trees, in citrus orchards and on plants of Chrysanthemoides monilifera, showing intra-specific divergences according to their host plants. Interestingly, the invasive mealybug populations from Spanish orchards clustered together with the population on citrus from Limpopo Province (South Africa), sharing COI haplotypes. This result pointed to an optimum location to collect natural enemies against the invasive mealybug. A total of 14 parasitoid species were recovered from Delottococcus spp. and identified to genus and species level, by integrating morphological and molecular data. A parasitoid belonging to the genus Anagyrus, collected from D. aberiae in citrus orchards in Limpopo, is proposed here as a good biological control agent to be introduced into Spain.

Development and thermal requirements of the Nearctic predator Geocoris punctipes (Hemiptera: Geocoridae) reared at constant and alternating temperatures and fed on Anagasta kuehniella (Lepidoptera: Pyralidae) eggs

Knowledge of the optimal temperatures for development and survival of biological control agents is essential for efficient mass-rearing and introduction of natural enemies in augmentative biological control programs. We studied the effect of constant and alternating temperatures on development and survival of immature stages and the sex ratio at emergence of adults of the Nearctic generalist predator Geocoris punctipes (Say). We also determined its thermal requirements. They were reared in climatic chambers at alternating (21/11°C, 24/18°C, 27/21°C and 30/26°C ± 1°C) and constant temperatures (16.8°C, 21.5°C, 24.5°C and 28.3°C ± 1°C), RH 70 ± 10% and a 14 h photophase. Survival and development of G. punctipes were the same when reared at constant and alternating temperatures. Five instars were recorded in all temperature regimes. The duration of the egg stage and each instar, as well as that of total larval development were longer, and larval survival lower when reared at 16.8°C, 21/11°C, 21.5°C and 24/18°C than at 24.5°C, 27/21°C, 28.3°C and 30/26°C. The optimal temperature range for development and survival of G. punctipes is 24.5°C to 30°C, its lower development threshold temperature is 13.5°C and its thermal constant 295.9 DD. Sex ratios were not significantly different from 1 : 1 male : female ratio in all temperature regimes. There is an excellent match between the temperature regimes at which the prey Tuta absoluta (Meyrick) and predator G. punctipes are active, which indicates that this predator will function well in crops where this pest is present.

Population biology and epidemiology of plant virus epidemics: from tripartite to tritrophic interactions

Natural enemies have long been used in biological control programs to mitigate the damage caused by herbivory. Many herbivorous insect species also act as plant virus vectors, enabling virus transmission from plant to plant and hence disease development in a plant population. Whilst an intuitive assumption would be to expect a decrease in vector numbers to lead to subsequent reductions in virus transmission, recent evidence suggests that introduction of natural enemies (parasitoids and predators) may in some cases increase plant virus transmission while at the same time reducing vector numbers. In this paper we review the evidence for plant-virus-vector-natural enemy interactions, the signalling mechanisms involved and their implications for virus transmission, and show how a modelling approach can assist in identifying the key parameters and relationships involved in determining the disease outcome. A mathematical model linking the population dynamics of a vector-parasitoid system with virus transmission was used to investigate the effects of virus inoculation and acquisition rates, parasitoid attack rate and vector aggregation on disease dynamics across a wide range of parameter value combinations. Virus spread was found to increase with enhanced inoculation, acquisition and parasitoid attack rate but decrease with high levels of vector aggregation.

An innovative method for the biological control of Alternanthera philoxeroides

AbstractBiological invasion has become a serious global environmental problems and been considered as an important component of global change^1-2^. Invasions by alien species can have an impact at several levels of ecological complexity from genes to ecosystems^3-4^. Invasive alien species had seriously threated the biodiversity and natural ecosystems in China^5^, and caused economic losses by more than US$7 billion every year^6^. Alternanthera philoxeroides, commonly known as Alligator weed, is an invasive amphibious plant^7^. The effect of physical methods such as mechanical or artificial salvage, removal of A. philoxeroides were very limited. Moreover, these measure should be carried out very carefully or would easy lead to its rebound^8^. The mainly biological control methods of A.philoxeroides is the introduction of natural enemies including Arcola malloi and Amynothrips andersoni^9^. However, the introduction of natural enemies had little control effect on A. philoxeroides especially in terrestrial conditions, where the stems of A. philoxeroides lignified^9-12^. Here we found that Humulus Scandens (H. japonicus) can better inhibit the invasion of A. philoxeroides by means of interspecific competition which could be an ideal biological control method to control the invasion of A. philoxeroides.