Efficiency Of Biological Control Research Articles

Iranian Trichogramma: ITS2 DNA characterization and natural Wolbachia infection

Egg parasitoids of the genus Trichogramma (Hymenoptera: Trichogrammatidae) are important natural enemies of many lepidopterous pests in agricultural and forest areas. Because the use of indigenous Trichogramma populations/species can significantly increase the biological control efficiency, the characterization of endemic populations and precise species identification is important. In this study, Trichogramma wasps were collected from parasitized eggs of several lepidopteran pests in Northern and Central Iran. Seven Trichogramma species were identified based on the morphology and the nucleotide sequence, size and restriction profile (PCR-RFLP) of the internal transcribed spacer 2 (ITS2) region of the rDNA of T. brassicae Bezdenko, T. cacoeciae Marchal, T. embryophagum Hartig, T. evanescens Westwood, T. euproctidis Girault, T. pintoi Voegele and T. tshumakovae Sorokina. This is the first report of T. euproctidis in Iran. Additionally, natural populations were surveyed for the prevalence of Wolbachia. Two populations of T. brassicae were found to be infected by a single Wolbachia strain which was identified by using a multi-locus sequencing approach.

The effect of ground vegetation management on competition between the ants Oecophylla longinoda and Pheidole megacephala and implications for conservation biological control

In tropical Africa and Asia, two species of the predatory ant genus, Oecophylla, play a crucial role in protecting tree crops against pests and enhancing the quality of fruits and nuts. As predatory effectiveness is influenced by the presence of other dominant ant species, understanding the ecological factors at work in agroecosystems lies at the basis of conservation biological control. Over three and a half years, the effect of ground vegetation management on the beneficial tree-nesting ant Oecophylla longinoda (Latreille) and its competitor, the ground-nesting ant, Pheidole megacephala (Fabricius), was studied in a citrus orchard in Tanzania. When ground vegetation was present, P. megacephala tolerated O. longinoda and to some extent cohabited with this ant in citrus trees. However, after clean cultivation, P. megacephala displaced O. longinoda from tree crowns and became the sole occupant of the majority of trees. Displacement could be reversed by reversing the weed management regime, but this took time. Two years after the establishment of ground vegetation about half of the trees were colonized by Oecophylla only. Maintaining ground vegetation in tree crop plantations benefits the establishment and abundance of Oecophylla over Pheidole and is recommended in order to improve the efficiency of biological control of tree pests. The use of Amdro ant bait (hydramethylnon) to control P. megacephala is discussed. Boosting agroecological innovations, such as the one described in this paper, could benefit smallholder producers.

Interspecific interference competition between Encarsia formosa and Encarsia sophia (Hymenoptera: Aphelinidae) in parasitizing Bemisia tabaci (Hemiptera: Aleyrodidae) on five tomato varieties

Abstract Interspecific competition between Encarsia formosa and Encarsia sophia, two major parasitoids of Bemisia tabaci, and the influence of five tomato varieties on competition outcome were investigated under laboratory conditions. E. formosa parasitized more B. tabaci than E. sophia when in single wasp assays on any of the tomato varieties investigated. When B. tabaci nymphs were exposed to both wasp species (either simultaneously or sequentially), the number of B. tabaci nymphs parasitized by either wasp species was significantly decreased compared to the sole access condition. Total mortality of B. tabaci was increased when B. tabaci nymphs were exposed to both wasp species compared to only one wasp species. Thus competition between E. formosa and E. sophia apparently reduced parasitoid offspring numbers, but not the efficiency of biological control. In fact, control efficiency was enhanced in some cases, particularly on tomato variety Huangtuoyuan (HTY). When wasps were allowed sequential access to hosts, interference occurred through host feeding by the second wasp, especially if it was E. sophia. The effect of different tomato varieties was not significant.

A sophisticated life history strategy in a parasitoid wasp: Producing univoltine and multivoltine phenotypes in a local population

Insects may adopt a range of strategies such as diapause, migration and phenotypic plasticity to achieve maximal survival and reproduction in response to the environment. However, the phenotypic plasticity of voltinism in local populations of biological control agents is still poorly understood, making evaluation of biological control efficiency difficult. Here we report our two years’ work on a parasitic wasp, Platygaster demades Walker (Hymenoptera: Platygasteridae), a parasitoid of apple leaf-curling midge, Dasineura mali Kieffer (Diptera: Cecidomyiidae). P. demades produces aestivating and non-aestivating phenotypes at the embryonic stage over the season. It regulates the frequency and duration of aestivating phenotypes from the late spring to mid autumn and adjusts the embryonic developmental rate of non-aestivating phenotypes from the early to late autumn, producing univoltine, bivoltine, trivoltine and quadrivoltine phenotypes over the season. The regulation of aestivation frequency and duration is a temporal risk-spreading strategy for maximal survival, i.e., when the future food source is expected to be short the wasp regulates its population by entering aestivation in a frequency and duration concordant with the expected scale and duration of food shortage to avoid massive mortality. This strategy helps maintain a large overwintering population size for the next season. The adjustment of the embryonic developmental rate for the non-aestivating phenotype from the early to late autumn is an adaptive developmental strategy for maximal synchronization with the host, D. mali, i.e., the later the D. mali larvae become mature, the faster the parasitoid embryos develop. This strategy ensures that both aestivated and non-aestivated individuals reach a complete synchronization with the emergence of their hosts in the next spring.

Effects of Relay-Intercropping Sorghum With Winter Wheat, Alfalfa, and Cotton on Lady Beetle (Coleoptera: Coccinellidae) Abundance and Species Composition

Creating conditions that enhance the abundance of resident populations of natural enemies in agroecosystems is considered critical to the efficiency of biological control of insect pests. We conducted a study to determine the potential of relay-intercropping for enhancing the abundance of aphidophagous lady beetles in sorghum. A relay-intercropping system consisting of alfalfa, winter wheat, and cotton as intercrops and sorghum as a main crop was compared with sorghum monoculture plots at two study sites in OK from 2003 to 2006. Lady beetles and aphids were sampled throughout the season using sticky traps and field counts on individual sorghum plants. Results from sticky traps and field counts show that differences in abundance and species composition of lady beetles between intercropped and monoculture sorghum were not statistically different during each year of study. Also, the lady beetle-greenbug ratios in relay-intercropped and monoculture plots were not significantly different. Lack of significant effects of relay-intercropping in our study may have been attributable to the confounding effects of spatial and temporal scale and the low number of aphids and other alternative prey in the intercrops compared with high incidence of corn leaf aphids in sorghum early in the season.

ECOLOGIZATION OF PHYTOPHAGES POPULATION CONTROL MEASURES, AS THE MEANS OF ENTOMOLOGICAL AGROBIODIVERSITY CONSERVANCY AND REHABILITATION

The wide introduction of biological methods of pests control on main vegetables and potato promotes obtaining of environmentally safe products for baby and dietic nourishment as well as preservation of entomological agrobiodiversity. Selected new strain B. thuringiensis 0376 have shown the high biological population control efficiency not only against Phtorimea operculella Zel. during the vegetation and the storage of potato yield but also against Brevicoryne brassicae L. on the cabbage fields. At single application the additional stored cabbage yield made out 59 c/ha (90% to control).

Cereal aphid control by generalist predators in presence of belowground alternative prey: Complementary predation as affected by prey density

Summary Generalist predators are important antagonists of pest species in agroecosystems. Increasing populations of alternative prey through detrital subsidies is one way to foster these predators. However, alternative prey may also distract generalist predators from their prey thereby diminishing the efficiency of biological control. To develop reliable predictions for biological control, it is essential to evaluate the relative importance of generalist predators, pests, alternative prey and their respective interactions. We investigated the effects of an assemblage of generalist predators on the grain aphid Sitobion avenae in winter wheat. Treatments with 10, 100 and 1000 aphids were established inside 2 m 2 sized caged plots with control and reduced density of predators. Three weeks after the experiment started, samples were taken to estimate the size of aphid populations and those of alternative prey. Three prey taxa were significantly reduced by generalist predators: the grain aphid S. avenae (Aphidina), the click beetle Adrastus pallens (Elateridae) and the springtail Isotoma viridis (Collembola). Springtails were decreased by generalist predators independent of aphid densities, indicating complementary predation of springtails and aphids. At high aphid densities, grain aphid population peaks were decreased to the threshold level of economic damage, demonstrating efficient aphid suppression by the predator community. Click beetle numbers declined only at low and medium aphid densities. The results suggest that generalist predators preferentially fed on click beetles at low and medium aphid densities and switched to aphids at high aphid densities. Early-season predators likely had the greatest influence on aphid suppression. Our results indicate that alternative prey from the belowground system forms a substantial food resource for generalist predators, suggesting that the belowground subsystem modulates predator–prey interactions above the ground.

Predator mite application methods for biological control of twospotted mites in hops

The efficacy of a novel air stream predator mite application method for the control of twospotted mites (TSM Tetranychus urticae) in hops was compared with a standard teaspoon release method Predator mites (Phytoseiulus persimilis) were successfully established with a single release using both application methods and TSM declined to low numbers during the monitoring period Application of predator mites with a delivery device attached to a conventional leaf blower mounted on a quad bike was equally effective and at least four times faster than hand application There was no evidence of any physical damage to mites applied with the mite blower device The potential of the air stream application method to improve the efficiency of biological control of TSM using predator mites is discussed

Eficiência técnica e econômica do controle biológico da traça-do-tomateiro em ambiente protegido

A eficiência técnica e econômica do controle da traça-do-tomateiro (Tuta absoluta) pelo parasitóide Trichogramma pretiosum foi avaliada em ambiente protegido na área de um produtor do município de Luziânia-GO, durante o verão de 1999-2000. O trabalho foi conduzido em duas casas de vegetação, sendo cada uma delas submetida aos seguintes regimes de controle de pragas: (1) prática do produtor: consistiu em pulverizações de inseticidas de acordo com a necessidade, em rotação com os produtos deltametrina, abamectin, Bacillus thuringiensis (nas doses recomendadas) e detergente 0,5%; (2) liberações inundativas de T. pretiosum associada com pulverizações semanais de B. thuringiensis em formulação concentrada emulsionável (na dose recomendada). As medidas de controle foram iniciadas logo após a constatação dos primeiros adultos da traça-do-tomateiro. A liberação massal consistiu na colocação de duas cartelas por semana (20x30 cm) de ovos parasitados por T. pretiosum que foram gradualmente aumentadas até que atingisse seis cartelas por semana por ocasião da colheita do tomate. Semanalmente, foram coletados 50 folíolos de tomateiro ao acaso em cada casa de vegetação. O número de ovos foi determinado, em laboratório e mantidos em câmaras climatizadas para a constatação das lagartas ou parasitismo. A produtividade e o dano nos frutos foram determinados semanalmente em 50 tomateiros escolhidos ao acaso em cada tratamento. A produtividade com controle biológico foi de 6.160 bandejas/600g e com controle químico foi de 6.833 bandejas/600g. Os custos variáveis da produção foram de R$ 3,9 mil e R$ 4,7 mil para o sistema com controle biológico e químico, respectivamente. O limite de quebra de safra permitido para ambos sistemas de produção, indicado pela margem de segurança econômica, foi maior para o controle biológico (61,7%). O coeficiente de eficiência econômica do controle biológico foi significativo (2,62) e a taxa interna de retorno (24,9%) confirmou a viabilidade econômica do sistema de produção de tomate utilizando o controle biológico com T. pretiosum.

Survey of leafminers and their parasitoids to find endosymbionts for improvement of biological control

Agromyzid leafminers cause serious pest problems in Japan. These leafminers are parasitized by their native parasitoids. The objective of our research is to find symbionts that may be useful in improving the biological control of Agromyzid leafminers by using their native parasitoids in Japan. Among the four species of leafminers, we detected two strains of Wolbachia from Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) and Liriomyza bryoniae (Kaltenbach) (Diptera: Agromyzidae). Although Wolbachia induces strong cytoplasmic incompatibility (CI) in L. trifolii , the level of Wolbachia infection in the population was not fixed and it was maintained at frequencies that must be regarded as unstable. Among the 15 species of leafminer parasitoids, we found a Wolbachia in Hemiptarsenus varicornis (Girault) (Hymenoptera: Eulophidae) and a Rickettsia in Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae). H. varicornis was observed to be infected with Wolbachia very similar to that of the native leafminer L. bryoniae . This Wolbachia strain did not induce CI or parthenogenesis in H. varicornis . N. formosa is thelytokous and infected with Rickettsia , in practically all populations that were studied, the Rickettsia infection has reached fixation. Many leafminer parasitoids including N. formosa , belong to the family Eulophidae. It is possible that the Rickettsia of N. formosa may be used to render other Eulophidae thelytokous as well as a method to increase the biological control efficiency.

Comparison of thermal tolerance of seven native species of parasitoids (Hymenoptera: Eulophidae) as biological control agents against Liriomyza trifolii (Diptera: Agromyzidae) in Japan

The efficiencies of seven native species of eulophid parasitoids (Pnigalio katonis, Hemiptarsenus varicornis, Diglyphus isaea, D. minoeus, D. pusztensis, Chrysocharis pentheus and Neochrysocharis formosa) as biological control agents against Liriomyza trifolii in a greenhouse were evaluated based on their thermal tolerance in development and reproduction. All of them are solitary and idiobiont parasitoids, and their adults kill hosts directly by feeding on the hosts. Based upon their thermal tolerance, the species could be roughly classified into two groups, i.e., H. varicornis and N. formosa which are more adapted to high temperatures, and the other five species which are more adapted to low temperatures. In biological control, host killing by host-feeding is profitable in the release step, but becomes unprofitable in the mass-production step because it does not result directly in production of progeny. Hence, an evaluation method based on biological control efficiency (BCE) is proposed in this study as a comprehensive criterion for evaluating the efficiency of the parasitoids as biological control agents. The thermal tolerance and BCE clarified in this study revealed that D. isaea should be used in cool seasons and N. formosa in hot seasons, based on a borderline temperature of 20 to 25°C in the greenhouse.

Biological Control Efficiency of Fusarium Wilt of Tomato by Nonpathogenic Fusarium oxysporum Fo-B2 in Different Environments

ABSTRACT Efficiency of nonpathogenic Fusarium oxysporum Fo-B2 for the biological control of Fusarium wilt of tomato, caused by F. oxysporum f. sp. lycopersici CU1, was examined in different environments: a growth chamber with sterile soil-less medium, a greenhouse with fumigated or nonfumigated soil, and nonfumigated field plots. Inoculation of Fo-B2 onto tomato roots significantly reduced the severity of disease, but the efficiency of disease suppression decreased as the experimental environment became less controlled. Relationships between the recovery of Fo-B2 from hypocotyls and the disease severity indicated that the biocontrol agent was most effective when it colonized vascular tissues intensively. Moreover, the degree of Fo-B2 colonization was greatly reduced when the seedlings were grown in nonfumigated soil. Dose-response models (negative exponential, hyperbolic saturation, and logistic) were fit to observed data collected over a range of inoculum densities of the pathogen and the antagonist; the logistic model provided the best fit in all environments. The ratios of an 50% effective dose parameter for Fo-B2 to that of CU1 increased as the environment became less controlled, suggesting that environmentally related efficiency reduction impacted the antagonist more than the pathogen. The results suggest that indigenous soil microbes were a primary factor negatively influencing the efficiency of Fo-B2. Therefore, early establishment of the antagonist in a noncompetitive environment prior to outplanting could improve the efficacy of biological control.

Crescimento, esporulação e viabilidade de fungos entomopatogênicos em meios contendo diferentes concentrações do óleo de nim (Azadirachta indica)

A associação de extratos de origem vegetal com fungos entomopatogênicos pode aumentar a eficiência do controle biológico de pragas, reduzir custos e impactos ambientais. No presente trabalho, avaliou-se, através da concentração inibitória mínima, o efeito do óleo de nim (NIM-I-GO) sobre o crescimento, esporulação e viabilidade de Metarhizium anisopliae, Beauveria bassiana e Paecilomyces farinosus. Utilizou-se o meio BDA, contendo diferentes concentrações de óleo de nim (C1: 5% de óleo de nim, e sucessivamente concentrações iguais a ½ da concentração anterior, até C11: 0,0048% de óleo de nim). O óleo de nim reduziu o crescimento de colônias de B. bassiana e P. farinosus, que não diferiram significativamente do controle apenas na concentração C11, mas para M. anisopliae o mesmo efeito foi observado com 0,039% de óleo de nim (C8). A esporulação também foi significativamente reduzida pelo óleo de nim, exceto na concentração C11 para B. bassiana; contudo, não se verificou efeito do óleo na viabilidade de esporos dos fungos.

Epidemiological dynamics and the efficiency of biological control of soil‐borne disease during consecutive epidemics in a controlled environment

• A combination of experimentation and modelling is used to examine the role of epidemiological dynamics on the production and infectivity of inoculum and the efficiency of biocontrol by Trichoderma viride during consecutive epidemics of damping-off disease caused by the pathogen Rhizoctonia solani in crops of radish. • Changes in the net infectivity of inoculum at the beginning of first and second crops caused a switch in epidemiological dynamics. Epidemics of first crops were dominated by secondary infection leading to amplification of inoculum so that epidemics of second crops were overwhelmingly determined by primary infection. • The biocontrol agent reduced primary infection and hence parasitic amplification of inoculum in both first and second crops but the efficiency of control dropped from 91.7% in first crops to 64.8% in second crops, with sudden outbreaks of disease in second crops which had previously been disease-free. • We conclude that parasitic amplification can cause a rapid build-up of disease and inoculum over consecutive crops, leading to loss in the efficiency of biocontrol. This form of inoculum production is supplemented by saprotrophic infestation which can result in sudden outbreaks of disease in protected crops where control of disease had previously been fully successful.

Fungicides and some biological controller agents effects on the growth of fusarium oxysporum causing paprika wilt: Wirkung von fungiziden und einigen biologischen kontrollwirkstoffen auf das wachstum des paprikawelke verursachenden fusarium oxysporum

Soil samples from both healthy and diseased paprika roots were tested to identify their mycoflora. Thirty-one species belonging to 16 genera were collected from rhizosphere and rhizoplane samples. The most frequently isolated fungi were Aspergillus flavus, A. niger, A. terreus, Fusarium oxysporum, Penicillium jensenii and Trichoderma harzianum. Fusarium oxysporum was the most common Fusarium species in the rhizoplane samples of diseased roots and identification was confirmed by RAPD-PCR technique. Trichoderma harzianum, T. pseudokoningii and Glioclaium roseum were chosen to study their biological control efficiency against Fusarium oxysporum. These fungal species reduced the percentage of seedling infection to 25, 40 and 50%, respectively. With the increasing of fungicide (Folicur and Ridomil) doses the dry weight of F. oxysporum decreased. Also, the increasing of fungicide dose lead to a slight decrease in the dry weight of T. harzianum, T. pseudokoningii and Glioclaium roseum.

The effect of temperature on the functional response of Phytoseiulus persimilis (Acari: Phytoseiidae).

Environmental variables, such as temperature, are important in determining the efficiency of biological control in ornamental crops. This paper examines the effect of temperature on the functional response of adult female Phytoseiulus persimilis to eggs of the spider mite, Tetranychus urticae. The functional response was determined using a new functional response assay technique with plant stems as an arena, rather than leaf discs. The use of plant stems allows the influence that plant structure has on predation to be incorporated into the assay. Control assays were also used (without predators) to estimate natural losses of prey. The data were analysed using a binomial model, with the use of Abbot's formula to correct for the losses in the controls. A combined equation to describe the effect of temperature and prey density on the predation rate of Phytoseiulus persimilis was derived. The results showed that more prey are eaten as the temperature increases from 15 degrees C to 25 degrees C, but the number of prey eaten then declines at 30 degrees C, although not to the levels seen at 20 degrees C. The implication of these results for biological control in ornamental crops, where the temperature can often exceed 30 degrees C, is discussed.

Biological Control of Black Rot ( Xanthomonas Campestris Pv. campestris ) of Brassicas with an Antagonistic Strain of Bacillus Subtilis in Zimbabwe

Biological control efficiency of an antagonistic, endophytic strain of Bacillus subtilis (strain BB) was evaluated against three strains of the black rot pathogen, Xanthomonas campestris pv. campestris (Xcc), in four Brassica crops (cabbage, cauliflower, rape and broccoli) grown during three consecutive growing seasons and on two soil types, in two different areas in Zimbabwe. Strain BB controlled the disease caused by strain Xcc B-147 in all Brassica crops during the dry and short rainy seasons. A similar effect was observed in cabbage using the strain Xcc 33908. Biological control was effective in broccoli, but not in cabbage and rape during the main rainy season in clay loam soil and limited biological control effect was still observed when these crops were grown in sandy loam soil. The endophytic colonisation of cabbage roots by strain BB was confirmed by immuno-blotting during the whole growing season. Biological control of black rot with strain BB is discussed in relation to its effect on Xcc strains, Brassica crops and to the effect of weather and soil conditions.

The Consequences of Ant-Attendance to the Biological Control of the Red Wax Scale Insect Ceroplastes rubens by Anicetus beneficus

The effects of an attendant ant (Lasius niger) on the host-parasitoid system of the red wax scale insect (Ceroplastes rubens) and its parasitoid wasp (Anicetus beneficus) and in relation to biological control efficiency of the wasp were examined by behavioural field observations, ant exclusion experiments in the field, and field censuses of the host population density and the percentage of parasitism. Parasitoids were frequently observed to interrupt their ovipositional behaviour due to interactions with ants attending host aggregations. Ant-exclusion experiments revealed that ant-attendance caused a decrease in the percentage parasitism and consequently an increase in the growth rate of the host population. The results of field censuses showed that, under the natural conditions in which some generalist ant species usually attended the host aggregations, host density remained at a high level or gradually increased over a 5-year period. Inverse density dependence was detected in the parasitism, which was expected from the density-biased defensive effects of ant-attendance. Overall, these results indicate that ant-attendance on C. rubens restricts the ovipositional ability of the parasitoid and thus reduces the effectiveness of the parasitoid as a control agent of C. rubens.

チリカブリダニによるハウス栽培作物のハダニの生物的防除のシミュレーション ２．モデルの適合性と必須データ

前報(齋藤ら,1996)で開発された差分型のチリカブリダニ-ナミハダニの生物的防除予測シミュレーションモデルの適合性を高度施設園芸設備で栽培されたイチゴとビニールハウス栽培キュウリの2環境における防除実験に基づいて検討した。その結果,イチゴではカブリダニの捕食率を実験値よりも13%落とし,チリカブリダニ雌:ナミハダニ雌の比が約1:7でチリの分散が起きるとおくと良い一致が得られ,またキュウリでは捕食率を30%低下させ,導入時の定着率を0.8とした時に良い一致がみられた。これらの率変数の変更は,それぞれの植物のサイズや形態および実験方法からみて妥当なものと考えられ,それゆえに本モデルは今後の防除実用化に有用である。また,シミュレーションの過程でチリカブリダニ利用にとって必須であると考えられたいくつかの調査項目について検討した。

Crystallographic and morphological studies of the celestite skeleton of the acantharian species Phyllostaurus siculus

The crystallography and morphology of the celestite (SrSO 4 ) skeleton of the acantharian species Phyllostaurus siculus have been studied by electron microscopy, electron diffraction and optical microscopy. The skeleton is composed of 20 spicules, radiating from a central point, which are shown to be divided into three groups according to their morphology. High-resolution transmission electron microscopy (HRTEM) has confirmed the single-crystal nature of each spicule. The spicules connect via lateral wing structures, the crystallographic orientations of which have been determined. The precise arrangement of the spicules has been established and is described in terms of the lateral wing attachments at the cell centre. The effects of crystallographical constraints, efficiency of spicule packing and biological control on spicule arrangement are discussed.