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PubMed2005

On the dynamics of flying insects populations controlled by large scale information.

We present a diffusion model adapted to an operational control of flying insects. The operational objective entails working with non-homogeneous regions and the corresponding non-uniform diffusion tensors. It the becomes necessary to study the problem of scale in order to justify the diffusion equation. We show that in typical cases, the spatial resolution must be coarser than 20 m and we have specified the appropriated time scales. We propose a method for computing the tensors at the given resolution, in relation to the landscape and the insects' species and a method for the numerical solution of the equations and present two applications.

Animals↗
PubMed1993

Random amplified polymorphic DNA markers for DNA fingerprinting and genetic variability assessment of minute parasitic wasp species (Hymenoptera: Mymaridae and Trichogrammatidae) used in biological control programs of phytophagous insects.

Biological control of insects that feed on our crops has become more practical in recent years by mass release of egg parasitoid microhymenoptera. Trichogramma species are now commercially reared and spread in commercial fields to control specific insect pests. Microhymenoptera species are, however, very small and morphologically indistinguishable within species, although strains of a given species differ in their efficiency to control specific insect pests. Traditional taxonomy is unable to differentiate microhymenoptera species at the strain level. It is becoming increasingly important to develop a reliable system to monitor genetic variations both within and between strains of commercially important microhymenoptera, to detect genetic drift occurring during several generations of multiplication, to protect patents, and to certify the lots of commercially released microhymenoptera. We have developed a system based on DNA markers to rapidly characterize individuals of five species of microhymenoptera from the genus Anaphes and Trichogramma including a new species of Anaphes not previously described. The main components of our system are a rapid and simple DNA micro-extraction method and fast DNA polymorphism analyses based on random amplified polymorphic DNA markers.

Animals↗
PubMed2002

Alternatives to methyl bromide treatments for stored-product and quarantine insects.

Methyl bromide is used to control insects as a space fumigant in flour and feed mills and ship holds, as a product fumigant for some fruit and cereals, and for general quarantine purposes. Methyl bromide acts rapidly, controlling insects in less than 48 h in space fumigations, and it has a wide spectrum of activity, controlling not only insects but also nematodes and plant-pathogenic microbes. This chemical will be banned in 2005 in developed countries, except for exceptional quarantine purposes, because it depletes ozone in the atmosphere. Many alternatives have been tested as replacements for methyl bromide, from physical control methods such as heat, cold, and sanitation to fumigant replacements such as phosphine, sulfuryl fluoride, and carbonyl sulfide, among others. Individual situations will require their own type of pest control techniques, but the most promising include integrated pest management tactics and combinations of treatments such as phosphine, carbon dioxide, and heat.

Animals↗
PubMed1976

Role of phermones and kairmones for insect suppression systems and their possible health and environmental impacts.

Insects produce pheromones as a chemical communication system to facilitate reproduction. These highly active chemical attractants have been synthesized for some of the most important insect pests, including the boll weevil, gypsy moth, codling moth, tobacco budworm, European corn borer, and several bark beetles. While none of the synthetic sex attractants have yet been developed for use in insect control, they offer opportunities for the future both as control agents and to greatly improved insect detection. Investigations are underway on insect trapping systems employing the phermones and on air permeation techniques to disrupt insect reproduction. The pheromones are generally highly species-specific and are not likely to pose hazards to nontarget organisms in the environment. Toxicological studies indicate that they are low in toxicity to mammals, birds, and fish, but adequate toxicological data are necessary before they can be registered for use in insect control. Another new class of compounds called kaironomes has been discovered. These chemicals are involved in the detection of hosts or prey by insect parasites and predators. Kairomones may prove useful in manipulating natural or released biological agents for more effective biological control of insect pests. No information is yet available on the toxicology of these chemicals.

Air↗
PubMed1995

Nonspiking local interneurons in insect leg motor control. I. Common layout and species-specific response properties of femur-tibia joint control pathways in stick insect and locust.

1. Locusts (Locusta migratoria) and stick insects (Carausius morosus) exhibit different strategies for predator avoidance. Locusts rely primarily on walking and jumping to evade predators, whereas stick insects become cataleptic, catalepsy forming a major component of the twig mimesis exhibited by this species. The neuronal networks that control postural leg movements in locusts and stick insects are tuned differently to their specific behavioral tasks. An important prerequisite for the production of catalepsy in the stick insect is the marked velocity dependency of the control network, which appears to be generated at the level of nonspiking local interneurons. We examined interneuronal pathways in the network controlling the femur-tibia joint of the locust middle leg and compared its properties with those described for the stick insect middle leg. It was our aim to identify possible neural correlates of the species-specific behavior with regard to postural leg motor control. 2. We obtained evidence that the neuronal networks that control the femur-tibia joints in the two species consist of morphologically and physiologically similar--and thus probably homologous--interneurons. Qualitatively, these interneurons receive the same input from the femoral chordotonal organ receptors and they drive the same pools of leg motoneurons in both species. 3. Pathways that contribute to the control of the femur-tibia joint include interneurons that support both "resisting" and "assisting" responses with respect to the motoneuron activity that is actually elicited during reflex movements. Signal processing via parallel, antagonistic pathways therefore appears to be a common principle in insect leg motor control. 4. Differences between the two insect species were found with regard to the processing of velocity information provided by the femoral chordotonal organ. Interneuronal pathways are sensitive to stimulus velocity in both species. However, in the locust there is no marked velocity dependency of the interneuronal responses, whereas in the same interneurons of the stick insect it is pronounced. This characteristic was maintained at the level of the motoneurons controlling the femur-tibia joint. Pathways for postural leg motor control in the locust thus lack an important prerequisite for the generation of catalepsy, that is, a marked velocity dependency.

Animals↗
PubMed1993

Insect pest control by copying nature using genetically engineered crops.

A 'copy Nature' strategy for insect pest control is presented which aims to be relatively sustainable and environmentally friendly. Many higher plant genes encoding insecticidal proteins exist in Nature which can be expressed in transgenic plants in a tissue or development-specific manner, or in response to environmental stimuli. These genes can either be expressed singly or in combination so as to enhance host resistance to insect pests. The results so far, which have been obtained mainly in the growth-room, are discussed in both a scientific and applied context. The feasibility of this technology, either as a partial substitution technology for synthetic chemicals or as a component in IPM systems, now needs to be evaluated in the farmer's field. If proven there, its long-term use may depend on promoting agronomic and farm management which minimizes the build-up of resistance in insect populations.

Carbohydrate Sequence↗
PubMed2002

Insect vision: controlling actions through optic flow.

Insects depend upon optic flow to supply much of their information about the three-dimensional structure of the world. Many insects use translational flow to measure the distance of objects from themselves. A recent study has provided new insights into the way Drosophila use optic flow to pick out a close target to approach.

Animals↗
PubMed1998

Controlled release of sugar and toxicant from a novel device for controlling pest insects.

A novel biodegradable device, designed for long-lasting residual effectiveness of feeding stimulant (sugar) and insecticide (dimethoate) against apple maggot files and other insects, was formulated. The device is an 8-cm diameter fruit-mimicking sphere, consisting of 42-50% sugar entrapped in a mixture of gelatinized corn flour and wheat flour in the presence of glycerin, and coated with a layer of latex paint containing dimethoate and sugar. We found that the outer layer of paint prevents cracking of the sphere upon drying and creates a barrier to control the release of both sugar and dimethoate. Releases of each ingredient were screened first by chemical analysis and then by bioassays in the laboratory and in field cages against apple maggot flies. Chemical analysis demonstrated strong potential for controlled release of water-soluble feeding stimulant and water-insoluble insecticide measured as a function of the amount of rainfall and duration of exposure time. Field results showed greater than 70% insecticidal activity after 11 weeks of sphere exposure in an orchard. This device has the potential to be used for a variety of insect-control applications through manipulating its shape, color and texture into forms known to be attractive to target insects, and by employing various toxicants designed to be effective against such insects.

Animals↗
PubMedDate not supplied

A new approach to insect-pest control--combination of neurotoxins interacting with voltage sensitive sodium channels to increase selectivity and specificity.

Voltage-sensitive sodium channels are responsible for the generation of electrical signals in most excitable tissues and serve as specific targets for many neurotoxins. At least seven distinct classes of neurotoxins have been designated on the basis of physiological activity and competitive binding studies. Although the characterization of the neurotoxin receptor sites was predominantly performed using vertebrate excitable preparations, insect neuronal membranes were shown to possess similar receptor sites. We have demonstrated that the two mutually competing anti-insect excitatory and depressant scorpion toxins, previously suggested to occupy the same receptor site, bind to two distinct receptors on insect sodium channels. The latter provides a new approach to their combined use in insect control strategy. Although the sodium channel receptor sites are topologically separated, there are strong allosteric interactions among them. We have shown that the lipid-soluble sodium channel activators, veratridine and brevetoxin, reveal divergent allosteric modulation on scorpion alpha-toxins binding at homologous receptor sites on mammalian and insect sodium channels. The differences suggest a functionally important structural distinction between these channel subtypes. The differential allosteric modulation may provide a new approach to increase selective activity of pesticides on target organisms by simultaneous application of allosterically interacting drugs, designed on the basis of the selective toxins. Thus, a comparative study of neurotoxin receptor sites on mammalian and invertebrate sodium channels may elucidate the structural features involved in the binding and activity of the various neurotoxins, and may offer new targets and approaches to the development of highly selective pesticides.

Amino Acid Sequence↗
PubMed2025

Abiotic conditions can modify the penetrance of transgene-based lethality systems for insect population control.

Modern genetic biocontrol techniques for insect pest management, when compared to chemical insecticide spraying, offer high species specificity and reduced environmental impact, and some of these methods require the environmental release of genetically modified (GM) insects. Because organisms exposed to different environments often show variability in phenotype and gene expression, it is likely that GM insects will also experience environmentally mediated variation, potentially compromising pest control efficiency. This study examines the impact of temperature and nutrition on the early embryonic Tet-off conditional lethality system in Drosophila melanogaster. By independently manipulating parental and offspring environments, we assessed how exposure to variable environments influenced the probability of larval hatching and the transcript abundance of the transgenic system. Our findings revealed that: (i) transgene performance distinctly responds to temperature and nutrition; (ii) thermal stress has a greater impact when embryos, rather than parents, are exposed; and (iii) extreme nutritional conditions can markedly reduce the penetrance of transgenic lethality. Although changes in transgene transcript abundance were observed across environments, these changes did not fully explain the phenotypic variation, suggesting that factors downstream of transcription probably drive variation in transgenic lethality.

Animals↗
PubMed1994

Polydnavirus infection inhibits synthesis of an insect plasma protein, arylphorin.

The wasp Campoletis sonorensis injects a segmented, double-stranded DNA polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. After parasitization, CsPDV protects the wasp egg and larva by selectively disabling the host's cellular immune response. Other host physiological systems including growth and development are affected to the apparent benefit of the parasite. To begin the characterization of the biochemical effects and mode of action of CsPDV on host growth, the titre of a developmentally regulated insect storage protein, arylphorin, was studied. Parasitized or virus-infected insects had substantially less circulating arylphorin than control insects. Fat bodies from parasitized larvae also synthesized less arylphorin in vitro. However, Northern blots of total RNA from parasitized and non-parasitized, control insects showed that the arylphorin transcript level was unaffected by parasitization suggesting a biochemical block at the translational level. In vitro translation followed by immunoprecipitation of arylphorin indicated that the mRNA was present and translatable at equal levels in both parasitized and control insects. Injection of purified virus elicited the response observed in naturally parasitized larvae, demonstrating that the effect on arylphorin synthesis is mediated, either directly or indirectly, by polydnavirus gene product(s).

Animals↗
PubMed1993

[Laboratory studies of the usefulness of biopreparation Dipel in reducing the german cockroach (Blattella germanica L.) population].

In the studies conducted for finding of biological factors effectively controlling insects of hygienic importance German cockroaches were subjected to the action of an insecticide containing spores of Bacillus thuringiensis var. kurstaki. One gram of the insecticide contained 25 miliard (US billion) spores with protein endotoxin crystals. The insects were given drinking water and food containing 1.0%, 0.5%, 0.25%, 0.125% of the initial preparation. The experiment was carried out on 1800 cockroaches. Half of them (600 mature insects differentiated for sex and age and 300 larvae in stage 1st of development) were treated with the preparation, the remaining insects served for control. The insects were kept at about 28 degrees C. After 9 days o the experiment in the group receiving 1% Dipel on food 76.4% mature insects and 83.0% larvae in 1st stage of development died. After 14 days all males died, and after 17 days died all females. In the control group died in that time 2.3% and 3.4% respectively. In case of lower per cent of the preparation in food the time of dying was prolonged, and at the lowest per cent it was 22 days. The study showed that Dipel effectively reduced the population of German cockroaches, and although in initial period its action was slower than that of chemical agents, it could be used for the control of these insects, especially as it in non-toxic for humans, warm-blooded animals and useful insects.

Animals↗
PubMedDate not supplied

[Genetic means for control of insect vectors of human diseases (author's transl)].

We divide genetical control methods in two major groups:--mechanisms operating between different species and an example is the attempt of control of A. gambiae in West Africa,--mechanisms operating in a single species with: gamma rays and chemical treatment for sterilisation, cytoplasmic incompatibility (ex.: C. pipiens). Genetical control also suppose the knowledge of biology and ecology of the target insect. This paper does not want to be an exhaustive review of this problem. Its only ambition is to try and expose the possible applications of genetics in the control of vectors.

Africa, Western↗
PubMedDate not supplied

[Analogs of juvenile hormones in the control of insects of medical or sanitary importance].

The growth and moulting or immature insects is related to three main groups of hormones : cerebral, ecdysonal and juvenile. Juvenile hormone analogues mark a new stage in the control of detrimental insects, and have significant advantages over the conventional insecticides. In order to establish the effectiveness of juvenile hormone analogues a series of biotests were performed : the wax pupal test, injections, systemic and topical applications, the treatment of food, pulverizations and exposure to vapors. In the laboratory, the efficiency of the analogues was tested against the following genera : Anopheles, Aedes, Culex, Culiseta, Musca, Stomoxys and Blattella, obtaining several effects, such as : lengthening of the larval stages, blocking of metamorphosis and ecdysis, blocking of the emergence of adults, morphogenetic ovicide, sterilizing and lethal effects, etc. Exploratory trials were performed in the field with compounds whose effectiveness had been demonstrated, against some Aedes, Musca, Stomoxys, Pediculus and Bovicola species. Laboratory experiments showed, however, that the insects might become resistant to juvenile hormone analogues.

Aedes↗
PubMed1989

Biological control of insect pests affecting man and animals in the tropics.

Biological control of pests affecting the health of man and animals is practiced in various forms throughout the tropics. In this paper, the use of parasitic viruses, bacteria, protozoa, predatory arthropods, and fish against pests such as various mosquitoes, tse tse flies, and screwworm flies as published in the literature are reviewed. Mention is also made of the usefulness and applicability of the sterile insect technique, genetic control by chromosomal aberrations, and the exploitation of various incompatabilities. These are reviewed against the background of the present state of technology and limited resources that exist in many tropical countries. Most authors maintain that due to the relative length of time required to get a biological control system working efficiently, and the perennial nature of most tropical pest species, there is often the need to initially reduce the pest population by conventional means. There will thus be a balance between biological and chemical control in most systems. Emphasis is placed on meeting the urgent need for the exchange of research and development information on biological control of pests affecting man and his animals in the tropics.

Animals↗