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PubMed2006

Assessing risks of releasing exotic biological control agents of arthropod pests.

More than 5000 introductions of about 2000 species of exotic arthropod agents for control of arthropod pests in 196 countries or islands during the past 120 years rarely have resulted in negative environmental effects. Yet, risks of environmental effects caused by releases of exotics are of growing concern. Twenty countries have implemented regulations for release of biological control agents. Soon, the International Standard for Phytosanitary Measures (ISPM3) will become the standard for all biological control introductions worldwide, but this standard does not provide methods by which to assess environmental risks. This review summarizes documented nontarget effects and discusses the development and application of comprehensive and quick-scan environmental risk assessment methods.

Animals↗
PubMed2002

The role of ants, especially the fire ant, Solenopsis geminata (Hymenoptera: Formicidae), in the biological control of tropical upland rice pests.

Predatory ants are omnipresent year-round in upland (dryland) rice fields in the Philippines. At least 14 species were identified of which the very aggressive Solenopsis geminata (Fabricius) and also Tapinoma sp. nr indicum Forel usually predominated. Some highly aggressive species, notably Pheidolegetonspp. and Bothriomyrmex dalyi Forel were localized. Solenopsis geminata flourished within many fields, not only during the crop season but also throughout dry season fallows where they remained aggressively predatory. Rice plants infested with brown planthopper Nilaparvata lugens (Stål) were usually found within a few hours and S. geminata workers were quickly recruited to N. lugens aggregates. Predation was usually incomplete and workers began to solicit the few remaining late instar or adult N. lugens survivors. These oviposited but no second generation nymphs appeared. There was a surge of recruited ants at the time of N. lugens egg hatch when surviving adults were also killed. Initially, S. geminataalone killed N. lugens aggregates less quickly than with the whole predator complex but ultimately its sole effect was as great as that of the complex. Scattered N. lugens adults, corresponding to numbers that initially colonize rice plants, were eliminated as quickly by S. geminata alone as by the predator complex. Tapinoma indicum occurring separately or with S. geminataon the same plant contributed to predation of N. lugens especially on young nymphs. Solenopsis geminataattacked other insects on rice notably leaffolders of which 97% mortality was recorded when they were exposed throughout egg and larval stages. The role of S. geminataas a predator of upland rice pests is discussed in the context of known biological control of pests of non-rice dryland crops in the tropics and sub-tropics by S. geminata and other Solenopsis spp.

Animals↗
PubMed2006

Development and validation of a sensitive and fast chemiluminescent enzyme immunoassay for the detection of genetically modified maize.

Proteins from the Cry 1 family, in particular Cry 1Ab, are commonly expressed in genetically modified Bt maize in order to control chewing insect pests. A sensitive chemiluminescent sandwich enzyme immunoassay for the detection of Cry1Ab protein from genetically modified Bt maize has been developed and validated. A Cry1Ab protein-specific antibody was immobilized on 96- or 384-well microtiter plates in order to capture the Cry1Ab toxin in the sample; the bound toxin was then detected by employing a second anti-Cry1Ab antibody and a horseradish peroxidase-labeled anti-antibody, followed by measurement of the enzyme activity with an enhanced chemiluminescent system. The chemiluminescent assay fulfilled all the requirements of accuracy and precision and exhibited limits of detection of a few pg mL(-1) Cry1Ab (3 or 5 pg mL(-1), depending on the assay format), which are significantly lower than that achievable using conventional colorimetric detection of peroxidase activity and also represent an improvement compared to previously developed Cry1Ab immunoassays. High-throughput analysis can be performed using the 384-well microtiter plate format immunoassay, which also allows one to reduce the consumption of samples and reagents. Validation of the assay, performed by analyzing certified reference materials, proved that the immunoassay is able to detect the presence of the Cry1Ab protein in certified reference samples containing as low as 0.1% of MON 810 genetically modified Bt maize. This value is below the threshold requiring mandatory labeling of foods containing genetically modified material according to the actual EU regulation.

Bacillus thuringiensis Toxins↗
PubMed2005

Baculoviruses-- re-emerging biopesticides.

Biological control of agricultural pests has gained importance in recent years due to increased pressure to reduce the use of agrochemicals and their residues in the environment and food. Viruses of a few families are known to infect insects but only those belonging to the highly specialized family Baculoviridae have been used as biopesticides. They are safe to people and wildlife, their specificity is very narrow. Their application as bioinsecticides was limited until recently because of their slow killing action and technical difficulties for in vitro commercial production. Two approaches for the wider application of baculoviruses as biopesticides will be implemented in future. In countries where use of genetically modified organisms is restricted, the improvements will be mainly at the level of diagnostics, in vitro production and changes in biopesticide formulations. In the second approach, the killing activity of baculoviruses may be augmented by genetic modifications of the baculovirus genome with genes of another natural pathogen. It is expected that the baculoviruses improved by genetic modifications will be gradually introduced in countries which have fewer concerns towards genetically modified organisms.

Animals↗
PubMed2005

Combined effect of biopesticides on the digestive enzymatic profiles of Cnaphalocrocis medinalis (Guenée) (the rice leaffolder) (Insecta: Lepidoptera: Pyralidae).

Plant extracts, especially botanical insecticides, are currently studied more and more because of the possibility of their use in plant protection. Many of the natural plant compounds and organic compounds used in the control of insect pests are known to affect digestive enzymes. When fed a diet of rice leaves treated with botanical insecticides and bacterial toxins in bioassays, activities of the digestive enzymes protease, amylase, and lipase in the rice leaffolder larvae are affected. Digestive enzyme activities were affected by botanical insecticides and bacterial toxins individually and in combination. When combined, the effect was more severe at low concentration. There were statistically significant differences (P < or = 0.05) in enzyme activities in combined and individual treatments. The combination of Btk and botanical insecticides caused a two-fold decrease in enzyme activity even at reduced concentration. Clear dose-response relationships were established with respect to enzyme activity. A synergistic effect of botanical insecticides and bacterial toxins was found when combined in low doses. These effects are most pronounced in early instars.

Amylases↗
PubMed2006

Toxicity assessment of metabolites of fungal biocontrol agents using two different (Artemia salina and Daphnia magna) invertebrate bioassays.

Fungal biocontrol agents (BCAs) have been marketed for control of crop pests, weeds, and diseases. However, BCAs may produce toxic metabolites, whose presence in the formulated products, in the crops and in the environment should be considered along with the associated risk. Two invertebrate models, viz. Artemia salina and Daphnia magna were used to assess the acute toxicity of seven BCA metabolites, characterized by different chemical nature and mode of action, namely alamethicin (ALA), paracelsin (PCS), antiamoebin (AAM), gliotoxin (GTX), destruxin A (DA), oosporein (OOS), and elsinochrome A (EA). The two invertebrates were very sensitive to all the metabolites examined, except OOS. The LC50s after 24 and 36 h exposures showed the following toxicity ranks: A. salina, DA > ALA > EA > GTX > AAM > PCS (LC50s ranging from 9.78 to 40.84 microg/ml at 24 h and from 2.92 to 18.56 microg/ml at 36 h); D. magna, DA > GTX = EA > ALA > PCS > AAM (LC50s ranging from 0.20 to 24.41 microg/ml at 24h and from 0.16 to 11.98 microg/ml at 36 h). LC50 of OOS to D. magna increased dramatically in 36 h exposure, compared to 24 h exposures (5.84 and 68.40 microg/ml, respectively). A. salina and D. magna proved to be suitable models for rapid and inexpensive screening of toxicity of BCAs at an early stage of product development.

Animals↗
PubMed2005

Phoresy of the entomopathogenic nematode Heterorhabditis marelatus by a non-host organism, the isopod Porcellio scaber.

Entomopathogenic nematodes are widespread in nature and commonly used in the biological control of insect pests. However, we understand little about how these organisms disperse. We show in a laboratory setting that the entomopathogenic nematode Heterorhabditis marelatus is phoretically dispersed by a non-host organism, the isopod Porcellio scaber. These species both inhabit tunnels excavated in the roots and lower stems of bush lupine (Lupinus arboreus) by the nematodes' primary prey, larvae of the ghost moth Hepialus californicus. Phoretic dispersal via P. scaber may play a role in the metapopulation dynamics of this nematode.

Animals↗
PubMed1997

Ecological implications of control strategies: arthropods of domestic and production animals.

The control of arthropods of veterinary importance represents a disturbance for the ecosystem and its animal community. This disturbance can influence the densities of target and non-target organisms and their associated indirect interactions in the food web, leading to reductions in the species richness and diversities in the communities involved. Finely tuned control affecting the target organism alone can have unexpected consequences, depending on the relationships between the target and other organisms within the food web. Broad-spectrum control methods will have more wide ranging and less predictable consequences. Modifications within the community caused by arthropod control can take place over generations and may not be immediately apparent. Most modern techniques of control are designed to minimize environmental impact by concentrating specifically on the target organism. The effects of control of arthropod pests of domestic and production stock must be seen against a background of more general effects caused by rural development which acts to modify the environment continuously over a long time span.

Animals↗
PubMed1998

Genetic variability in the area searched by a parasitic wasp: analysis from automatic video tracking of the walking path.

The ability of foraging hymenopterous parasitoid females to discover their hosts, and thus to be efficient agents in biological control programs, is likely to be related to the surface they are able to prospect per unit of time. However, this behavioural trait has never been accurately estimated, and its implication in female efficiency has never been really demonstrated. This paper provides an algorithmic method that can be used to estimate this trait from an automatic recording of the females' walking path. Using stochastic procedures simulating walking tracks, this trait is shown to be strongly related to the number of hosts that parasitoid females are able to attack per unit of time. This trait was estimated for individual females of Trichogramma brassicae Bezdenko (Hymenoptera; Trichogrammatidae). On average, females of this species are able to prospect about 28mm(2)s(-1). Finally, the genetic variation in this trait was studied using the iso-female line method. A significant genetic variability was observed. It provides the basic information that is necessary to start a genetic selection of mass-reared Trichogramma in order to improve their efficiency in controlling target pests in biological control programs. The functional and evolutionary implications of these results are discussed.

Journal Article↗
PubMed2003

Ecological characterization of Steinernema scarabaei, a scarab-adapted entomopathogenic nematode from New Jersey.

This study describes the basic ecological characteristics of the entomopathogenic nematode Steinernema scarabaei (Rhabditida: Steinernematidae) that was originally isolated from epizootics in scarab populations in New Jersey turfgrass areas. Under laboratory conditions, S. scarabaei infected a limited range of insect species and appeared best adapted to scarab larvae as hosts. It uses a widely ranging foraging strategy with a low attachment rate to mobile hosts on the soil surface but with excellent infection of sedentary host placed at >or=2 cm soil depth. It has a wide thermal activity range with optimum infectivity from 17.5 to 25 degrees C. Because of its foraging strategy and adaptation to scarab larvae as hosts, S. scarabaei has outstanding potential for the control of scarab pests.

Animals↗
PubMed2002

Phytoseiid predators suppress populations of Bemisia tabaci on cucumber plants with alternative food.

Phytoseiids are known to attack whiteflies, but it is an open question whether they can be used for biological control of these pest insects. Preselection experiments in the laboratory showed that two out of five phytoseiid species tested, Euseius scutalis and Typhlodromips swirskii, stood out in terms of their ability to develop and reproduce on a diet of Bemisia tabaci immatures. In this paper, we show that both predators are able to suppress whitefly populations on isolated cucumber plants in a greenhouse. Predatory mites were released 2 weeks in advance of the release of B. tabaci. To enable their survival and promote their population growth, they were provided weekly with alternative food, that is, Typha sp. pollen. A few weeks after whitefly introduction, the numbers of adult whiteflies on plants with predators were consistently lower than on plants without predators, where B. tabaci populations grew exponentially. After 9 weeks, this amounted to a 16- to 21-fold difference in adult whitefly population size. This shows that the two phytoseiid species are promising biocontrol agents of B. tabaci on greenhouse cucumber.

Animals↗
PubMed2026

Chromosomal-level genome assembly of minute pirate bug Orius nagaii Yasunaga, 1993 (Hemiptera: Anthocoridae).

Species of the genus Orius, diminutive predatory insects that act as natural enemies of other arthropods, are frequently employed in agricultural pest management for controlling various pests, such as thrips, mites, aphids, whiteflies, etc. However, the scarcity of high-quality genomic resources for these predators hinders our comprehension of their population evolution and predation ecology. Consequently, we assembled and annotated a chromosomal-scale genome of Orius nagaii by collating PacBio and Illumina sequencing and Hi-C genomic analysis techniques. The final genome assembly size 152.62&#x2009;Mb, with scaffold and contig N50 lengths of 11.53 and 2.39&#x2009;Mb, respectively. It is organized into 12 pairs of autosomes and a pair of XY sex chromosomes. The quality assessment of the genomic data with BUSCO revealed a completeness of 98.5% (n&#x2009;=&#x2009;1,367). Also, 11,917 protein-coding genes were discovered, with 94.28% of them having functional annotations. The high-quality genome of O. nagaii produced serves as a valuable resource for comprehending the interactions between predatory natural enemies and hosts, along with their evolutionary trajectories.

Animals↗
PubMed2001

Assessment of toxic potential of local Jordanian Bacillus thuringiensis strains on Drosophila melanogaster and Culex sp. (Diptera).

AIMS: To assess the toxic potential of different local Jordanian Bacillus thuringiensis isolates on larvae of Drosophila melanogaster and Culex sp. METHODS AND RESULTS: Scanning electron microscopy revealed the presence of spherical, bi-pyramidal, and bi-pyramidal and cuboidal parasporal bodies produced by the toxic isolates. Spherical inclusions dominated. The toxicity of the isolates to the two insects, determined using 24-well plates or vials, indicated that the 50% lethal concentration (LC50) of the bacterial suspension for D. melanogaster and Culex sp. larvae varied from 4.60 to 8.65, and from 5.30 to 6.74, respectively. CONCLUSION: Comparison of the LC50 values of isolate 82 with those of the reference strain B. t. israelensis showed that this isolate has a higher toxicity potential. SIGNIFICANCE AND IMPACT OF THE STUDY: Some local Jordanian B. thuringiensis isolates exhibit toxic potential that could be used to control some important pests, and could replace chemical pesticides.

Animals↗
PubMed2000

An epizootic of patent iridescent virus disease in multiple species of blackflies in Chiapas, Mexico.

Simulium blackfly larvae (Diptera: Simuliidae) were collected from rivers and streams at 500-1500 m a.s.l. in Chiapas State of southern Mexico. Among 45 sites surveyed over an area of 2300 km2 (around 15 degrees 15'N 92 degrees 20'W), some Simulium larvae from three sites were opalescent violet-blue, interpreted as patent infection with invertebrate iridescent virus (IIV). Dissection confirmed the presence of putative Iridovirus particles, 130nm diameter, but no IIV isolates were obtained from homogenates injected into Galleria mellonella (L) larvae (Lepidoptera: Pyralidae). All Simulium with patent IIV infection died before metamorphosis, whereas approximately 60% of asymptomatic Simulium survived to adulthood in the laboratory. During 1997, standard monthly samples from two parallel rivers 42-50 km north-west of Tapachula comprised the following species proportions (and rates of patent IIV infection): 41.8% (47%) Simulium mexicanum Bellardi complex, 31.3% (31.4%) S. rubicundum Knab, 10.1% (13.1%) S. paynei, 6.5% (2.9%) S. callidum (Dyar & Shannon), 6.3% (5.1%) S. ochraceum Walker complex, 3.1% (0.7%) S. downsi Vargas et al., 0.7% S. samboni Jennings and 0.2% S. metallicum Bellardi complex, showing a strong correlation between blackfly abundance and the prevalence of patent infection. An epizootic of IIV in January and February (infection rates 41-100%) was followed by absence of larvae (March-August) until the end of the rainy season, when numbers collected on nylon strings rose to approximately 1/cm with patent IIV infection rates of 0-12.5% during September-December. Further investigations are underway to isolate this IIV and assess its potential usefulness for biological control of Simulium pests and vectors of onchocerciasis.

Animals↗
PubMed2005

Analysis of the dynamics of adaptation to transgenic corn and crop rotation by western corn rootworm (Coleoptera: Chrysomelidae) using a daily time-step model.

Western corn rootworm, Diabrotica virgifera virgifera LeConte, has overcome crop rotation in several areas of the north central United States. The effectiveness of crop rotation for management of corn rootworm has begun to fail in many areas of the midwestern United States, thus new management strategies need to be developed to control rotation-resistant populations. Transgenic corn, Zea mays L., effective against western corn rootworm, may be the most effective new technology for control of this pest in areas with or without populations adapted to crop rotation. We expanded a simulation model of the population dynamics and genetics of the western corn rootworm for a landscape of corn; soybean, Glycine max (L.); and other crops to study the simultaneous development of resistance to both crop rotation and transgenic corn. Results indicate that planting transgenic corn to first-year cornfields is a robust strategy to prevent resistance to both crop rotation and transgenic corn in areas where rotation-resistant populations are currently a problem or may be a problem in the future. In these areas, planting transgenic corn only in continuous cornfields is not an effective strategy to prevent resistance to either trait. In areas without rotation-resistant populations, gene expression of the allele for resistance to transgenic corn, R, is the most important factor affecting the evolution of resistance. If R is recessive, resistance can be delayed longer than 15 yr. If R is dominant, resistance may be difficult to prevent. In a sensitivity analysis, results indicate that density dependence, rotational level in the landscape, and initial allele frequency are the three most important factors affecting the results.

Adaptation, Physiological↗
PubMed2000

Glucosinolate genetics and the attraction of the aphid parasitoid Diaeretiella rapae to Brassica.

The control of insect pests using parasitoids and carnivores has been successfully applied in protected cropping systems, orchards and forestry. Their success in annual field crops has been more limited due largely to the difficulties of attracting and maintaining a sufficient density of parasitoids in the crop before the levls of the insect herbivores become economically damaging. Parasitoids are known to be attracted to host-plant volatiles; thus, manipulating the host-plant chemistry may provide a means of enhancing the attraction of parasitoids to their prey. In this study we describe the differential attraction of the braconid wasp Diaeretiella rapae to two near-isogenic lines of Brassica oleracea which differ in a gene which alters the chemical structure of the isothiocyanates which are emitted following tissue damage. We demonstrate that, by enhancing the production of but-3-enyl isothiocyanate in B. oleracea and Brassica napus (oilseed rape), we can increase the attraction of D. rapae to these plants under standard field conditions.

Animals↗