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At least 415 records · Page 23Linked to original sources
PubMed1997

Proteinase inhibitors from Nicotiana alata enhance plant resistance to insect pests.

The ornamental tobacco (Nicotiana alata) produces one 6-kDa chymotrypsin inhibitor and four 6-kDa trypsin inhibitors from a single 40.3-kDa precursor protein. Three different approaches have been used to assess the potential of these proteinase inhibitors (PIs) in insect control. The first was an in-vitro approach in which all five inhibitors, the single chymotrypsin inhibitor or three of the four trypsin inhibitors were tested for their ability to inhibit gut protease activity in insects from four orders. The second approach was to incorporate the N. alata PIs in the artificial diet of the native budworm (Helicoverpa punctigera) and the black field cricket (Teleogryllus commodus). H. punctigera larvae and T. commodus nymphs had a significant (P<0.01) reduction in growth after ingestion of the PI and were more lethargic than insects on the control diet. Several of the H. punctigera larvae also failed to complete moulting at the third or fourth instar. The third approach was to express the N. alata PIs in transgenic tobacco under the control of the 35S CaMV promoter. When H. punctigera larvae were fed tobacco leaves expressing the N. alata PIs at 0.2% soluble protein, significant (P<0.01) differences in mortality and/or growth rate were observed.

Journal Article↗
PubMed1983

Control of the northern fowl mite on inanimate objects by fumigation: field studies.

Field studies were conducted to determine the efficacies of methyl bromide and sulfur dioxide as fumigants for northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), on egg flats and egg cases. Both fumigants killed the mites within 24 hr; however, sulfur dioxide had a repulsive irritating odor, which was retained in the cardboard egg flats and egg crates and persisted for several days after exposure to the gas. When used in accordance with the manufacturer's recommendations for fumigating enclosed trailers and vans to control insects that attack food products, methyl bromide gave excellent control of northern fowl mites infesting inanimate materials.

Animals↗
PubMed2004

The role of food plant and pathogen-induced behaviour in the persistence of a nucleopolyhedrovirus.

Insect baculoviruses can survive between epidemics as infectious particles external to the host. Many pathogens persist in reservoirs, i.e., microhabitats where survival is enhanced, for example due to protection from the degrading effects of UV irradiation. However, the probability of infecting new susceptible hosts is usually reduced. Persistence of pathogens and their movement in and out of reservoirs is an important, albeit little understood, aspect of insect pathogen ecology. This study investigated interactions between the behaviour of infected insect hosts, virus distribution and plant species on the persistence of the winter moth (Operophtera brumata) nucleopolyhedrovirus. Habitat influenced the persistence of infectious baculovirus in the field: virus on Sitka spruce (Picea sitchensis) and oak (Quercus robur) in forested areas retained more infectivity than virus on heather (Calluna vulgaris) in an unshaded habitat. Plant species per se did not directly affect the persistence of virus on the foliage of potted seedlings. Virally infected insects had altered behaviour and moved down plants relative to control insects, whereas in other systems larvae show height-seeking behaviour. Consequently, the majority of virus particles were distributed on plant stems. In two experiments (one using winter moth NPV and one Mamestra brassicae NPV) virus persisted better on plant stems relative to foliage. Neonate larvae were shown to be able to acquire infections from tree stems contaminated with a low level of virus. These data suggest that plant stems may be important reservoirs for between-year persistence of this pathogen. The observed virus-induced changes in host behaviour in winter moth could enhance the viral persistence by increasing the deposition of occlusion bodies in these reservoirs.

Animals↗
PubMedDate not supplied

Insecticide metabolism and selective toxicity.

Current research is focused on means to improve the environmental acceptability and selective toxicity of existing classes of insecticides and the search for new and species selective modes of insecticidal action. The study of species differences in metabolism and its modulation by changes in chemical structure is a vital component of this effort. The importance of metabolism is illustrated by examples from the major classes of insect control chemicals, namely organophosphorus and carbamate insecticides, DDT, pyrethroids and insect growth regulators.

Cholinesterase Inhibitors↗
PubMed2006

[Comparative susceptibility of Myzus persicae to 16 strains of Metarhizium spp. from different host insects and geographic regions].

The fungal biocontrol agents Metarhizium species and varieties have been widely applied for insect control but their targets rarely aim at sucking-type homopteran insects such as aphids. To search for fungal candidates against aphids, 16 strains of four varieties of two Metarhizium species, most of which originally infected foliage insect pests in Asia, Africa and America, were bioassayed to compare their virulence to Myzus persicae apterae. With each strain, each of three conidial suspensions was sprayed onto aphids in three Petri dishes (about 40 aphids per dish) in a Potter Spray Tower, resulting in deposits of conidia for low, medium and high dosage treatments (no. conidia/mm2). After spray, all aphids were reared at the regime of 25 +/- 1 degree C and 12:12 L:D and observed daily for counts of mycosed cadavers. As a result, 10 strains of M. anisopliae (Ma) and M. anisopliae var. anisopliae (Maa) caused 67%-100% mortalities at the high dosage of about 1000 conidia/mm2 within 7 days after spray whereas other strains, including M. anisopliae var. majus, M. anisopliae var. acridum, M. flavoviride var. minus, killed a very small number of aphids even at the high conidial dosage. Of the 10 strains, Ma 456 and Maa 3332 were highly virulent to the aphid species based the modeling of their time-dose-mortality data. The LC50 of the two strains were estimated as 113 and 260 conidia/mm2 on day 4, 32 and 43 conidia/mm2 on day 5, 17 and 26 conidia/mm2 on day 6, and only 11.4 and 19.9 conidia/mm2 on day 7, respectively. Thus, both strains are highly potential for use in microbial control of aphids.

Animals↗
PubMedDate not supplied

Vectors control importance on leishmaniasis transmission.

We reviewed the control of transmission of leishmaniasis regarding chemotherapy, reservoirs elimination, vaccination and insect control through the use of chemical insecticides. We also discussed complementary measures like monitoring traps, impregnated bednets and curtains, repelents, pheromones, biological control, etc. A cost comparison of insecticide interventions through the use of products belonging to the four main chemical groups was also done, comparing together conventional formulations versus a slow-release insecticide developed by the Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro. We finally did recommendations on the situation that would justify an insecticide intervention to control sandflies.

Animals↗
PubMed2004

The gut bacteria of insects: nonpathogenic interactions.

The diversity of the Insecta is reflected in the large and varied microbial communities inhabiting the gut. Studies, particularly with termites and cockroaches, have focused on the nutritional contributions of gut bacteria in insects living on suboptimal diets. The indigenous gut bacteria, however, also play a role in withstanding the colonization of the gut by non-indigenous species including pathogens. Gut bacterial consortia adapt by the transfer of plasmids and transconjugation between bacterial strains, and some insect species provide ideal conditions for bacterial conjugation, which suggests that the gut is a "hot spot" for gene transfer. Genomic analysis provides new avenues for the study of the gut microbial community and will reveal the molecular foundations of the relationships between the insect and its microbiome. In this review the intestinal bacteria is discussed in the context of developing our understanding of symbiotic relationships, of multitrophic interactions between insects and plant or animal host, and in developing new strategies for controlling insect pests.

Animals↗
PubMed2002

Control of resistant pink bollworm (Pectinophora gossypiella) by transgenic cotton that produces Bacillus thuringiensis toxin Cry2Ab.

Crops genetically engineered to produce Bacillus thuringiensis toxins for insect control can reduce use of conventional insecticides, but insect resistance could limit the success of this technology. The first generation of transgenic cotton with B. thuringiensis produces a single toxin, Cry1Ac, that is highly effective against susceptible larvae of pink bollworm (Pectinophora gossypiella), a major cotton pest. To counter potential problems with resistance, second-generation transgenic cotton that produces B. thuringiensis toxin Cry2Ab alone or in combination with Cry1Ac has been developed. In greenhouse bioassays, a pink bollworm strain selected in the laboratory for resistance to Cry1Ac survived equally well on transgenic cotton with Cry1Ac and on cotton without Cry1Ac. In contrast, Cry1Ac-resistant pink bollworm had little or no survival on second-generation transgenic cotton with Cry2Ab alone or with Cry1Ac plus Cry2Ab. Artificial diet bioassays showed that resistance to Cry1Ac did not confer strong cross-resistance to Cry2Aa. Strains with >90% larval survival on diet with 10 microg of Cry1Ac per ml showed 0% survival on diet with 3.2 or 10 microg of Cry2Aa per ml. However, the average survival of larvae fed a diet with 1 microg of Cry2Aa per ml was higher for Cry1Ac-resistant strains (2 to 10%) than for susceptible strains (0%). If plants with Cry1Ac plus Cry2Ab are deployed while genes that confer resistance to each of these toxins are rare, and if the inheritance of resistance to both toxins is recessive, the efficacy of transgenic cotton might be greatly extended.

Animal Feed↗
PubMed1994

Glucose metabolism in an insect Manduca sexta and effects of parasitism.

The metabolism of [1-13C]glucose was examined during the last larval stadium of an insect Manduca sexta (Lepidoptera: Sphingidae) parasitized by Cotesia congregata (Hymenoptera: Braconidae). Following injection, the isotopically substituted glucose was metabolized at a significantly lower rate by parasitized larvae than by normal, control insects. 13C enrichment was principally observed in [1-13C]trehalose in both groups. Randomization of the label at the triose phosphate step was evidenced by incorporation of 13C into C6 of trehalose. Parasitized and control larvae both synthesized [1,6-13C]glycogen but the relative amount of label observed in parasitized larvae was greater. The ratio of C6/C1 enrichment in trehalose and glycogen was significantly less in parasitized larvae. The rate of labelled trehalose and glycogen synthesis was relatively high when compared with the estimated rate of glycolytic glucose oxidation, and the difference in C6/C1 enrichment ratio between normal and parasitized insects was, therefore, not reflective of a difference in the rate of substrate cycling, but rather, was due to the increased synthesis of [1-13C]glycogen in parasitized larvae when compared with controls. Inhibition of glycolysis by administration of iodoacetate to normal larvae resulted in an increase in the incorporation of 13C into glycogen relative to glucose metabolized, suggesting that inhibition of glycolysis may be responsible for the higher level of glycogen synthesis observed in parasitized insects. In control larvae, significant 13C enrichment from [1-13C]glucose was observed in fat, but no evidence of lipogenesis was observed in parasitized insects. Iodoacetate had no observable effects on the relative amount of 13C incorporated into fat. Malonic acid and cyanide resulted in accumulation of 13C from [1-13C]glucose in several TCA cycle intermediates of normal larvae, but had little effect on the relative enrichments of trehalose, glycogen and fat.

Animals↗
PubMed2006

Mode of action of mosquitocidal Bacillus thuringiensis toxins.

Cry toxins from Bacillus thuringiensis (Bt) are used for insect control. Their primary action is to lyse midgut epithelial cells. In lepidopteran insects, Cry1A monomeric toxins interact with a first receptor and this interaction triggers toxin oligomerization. The oligomeric structure interacts then with a second GPI-anchored receptor that induces insertion into membrane microdomains and larvae death. In the case of mosquitocidal Bt strains, two different toxins participate, Cry and Cyt. These toxins have a synergistic effect and Cyt1Aa overcomes Cry toxin-resistance. We will summarize recent findings on the identification of Cry receptors in mosquitoes and the mechanism of synergism: Cyt1Aa synergizes or suppresses resistance to Cry toxins by functioning as a Cry membrane-bound receptor.

Animals↗
PubMed2005

Functional expression of lepidopteran-selective neurotoxin in baculovirus: potential for effective pest management.

Recombinant baculovirus expressing insect-selective neurotoxins derived from venomous animals are considered as an attractive alternative to chemical insecticides for efficient insect control agents. Recently we identified and characterized a novel lepidopteran-selective toxin, Buthus tamulus insect-selective toxin (ButaIT), having 37 amino acids and eight half cysteine residues from the venom of the South Indian red scorpion, Mesobuthus tamulus. The synthetic toxin gene containing the ButaIT sequence in frame to the bombyxin signal sequence was engineered into a polyhedrin positive Autographa californica nuclear polyhedrosis virus (AcMNPV) genome under the control of the p10 promoter. Toxin expression in the haemolymph of infected larvae of Heliothis virescens and also in an insect cell culture system was confirmed by western blot analysis using antibody raised against the GST-ButaIT fusion protein. The recombinant NPV (ButaIT-NPV) showed enhanced insecticidal activity on the larvae of Heliothis virescens as evidenced by a significant reduction in median survival time (ST50) and also a greater reduction in feeding damage as compared to the wild-type AcMNPV.

Animals↗
PubMed2001

Radio-frequency and microwave dielectric properties of insects.

Basic principles and definitions of dielectric properties of materials are presented. Data from the literature on the dielectric properties of insects are briefly reviewed and discussed in relation to insect control by selective dielectric heating. Because early measurements of the dielectric properties of insects were taken on bulk samples of insects (insect and air-space dielectric mixtures), a means for converting the dielectric properties, or permittivities, of bulk samples of particulate materials to those of the solid particles is described. The technique uses the Landau & Lifshitz, Looyenga dielectric mixture equation and information on the bulk densities of air-insect mixtures used for dielectric properties measurements along with the densities of the insects. Such converted data for the dielectric constants and loss factors of the insects are presented and collected for comparison with other measurements of insect tissues and permittivity determinations from more recent microwave measurements of these same parameters. Resulting data are presented for reference, and comparisons are presented and discussed briefly.

Animals↗
PubMed2001

Insecticidal and vertebrate toxicity associated with ethnobotanicals used as post-harvest protectants in Ghana.

Six plant species (Cassia sophera, Chamaecrista nigricans, Mitragyna inermis, Ocimum americanum, Securidaca longepedunculata and Synedrella nodiflora) traditionally used in Ghana to control insect pests of stored grain and legumes were screened in the laboratory at three concentrations (0.5, 1 and 5%, w/w) against four common storage pests (Rhyzopertha dominica, Callosobruchus maculatus, Sitophilus zeamais and Prostephanus truncatus). All the plants showed some ability to control all or some of the test insect species. Levels of efficacy varied according to test concentration with the highest concentration tested providing the best control. The S. longepedunculata plant induced the highest percent mortality and was the best at reducing emergence of the F(1) generation. The six plants were also incorporated into standard rat diet at two concentrations (1 and 5%, w/w) and fed to rats over a 6-week period to assess potential deleterious effects against vertebrates. None of the plants demonstrated any neurotoxicological or neurobehavioural effects to the rats over the course of the trial. However, S. longepedunculata and C. nigricans caused a significant reduction in rat growth rate when incorporated at 5% in the diet, induced cell hyperplasia in the liver, and reduced the mean weight of the liver and kidneys, compared to the control group of rats. Kidney pathology was affected only by the 5% concentration of S. longepedunculata which caused a reduced accumulation of alpha2mu-globulin. The implications of these results are discussed in the context of farmer usage of insecticidal plants for stored product protection.

Animals↗
PubMed1975

The control of bluetongue in an enzootic situation.

On account of the wide host range of bluetongue virus and its biological transmission by insects, control of the disease in an enzootic situation is based primarily on the active immunisation of susceptible animals as well as on the prevention of contact between the insect vectors and the susceptible hosts. In spite of their unquestionable value, the egg attenuated vaccines which are currently employed for prophylactic immunisation, have certain shortcomings. The existence of 16 known serotypes of bluetongue virus makes it difficult to achieve a very wide spectrum of immunity in sheep vaccinated once or twice only. The problems which are experienced with the immunisation of lambs born in spring are indicated. The present vaccine can also present problems when used in breeding animals. Furthermore, the costs involved in the annual vaccination of large numbers of animals are considerable. The need for a vaccine for cattle is indicated. Work is also being conducted at present on the development of an inactivated vaccine for use in sheep. The use of novel virological techniques may aid in the future development of absolutely safe and highly efficient vaccines against bluetongue.

Animals↗
PubMed1987

The biotechnology of Bacillus thuringiensis.

One of the challenges in the application of biotechnology to pest control is the identification of agents found in nature which can be used effectively. Biotechnology offers the potential of developing pesticides based on such agents which will provide environmentally sound and economically feasible insect control alternatives. Such an agent, the insect pathogen Bacillus thuringiensis, is the subject of intense investigations in several laboratories. Insecticides which use the entomocidal properties of B. thuringiensis are currently produced and sold worldwide; new products are currently in the development stage. Herein, the biology and genetics of B. thuringiensis and the problems associated with current products are critically reviewed with respect to biotechnology. Moreover, the economic and regulatory implications of technologically advanced products are evaluated.

Amino Acid Sequence↗
PubMed1994

Rhodnius prolixus: salivary antihemostatic components decrease with Trypanosoma rangeli infection.

Feeding behavior and some antihemostatic properties of the saliva of Rhodnius prolixus infected with Trypanosoma rangeli were studied and compared with those of uninfected controls. Insects with salivary gland infection pierced host skin more often and drew less blood and at a lower rate than controls when feeding on a rabbit. None of these differences was observed when feeding was performed through a membrane feeder. Salivary gland homogenates from infected insects, at 30 days after feeding/infection, had a significantly lower amount of total protein/salivary gland pair and less anticoagulant activity than controls. Also, infected salivary glands exhibited significantly reduced apyrase activities and reactive nitrogen groups when compared to controls. It is concluded that salivary infection of T. rangeli impairs the ability of the vector to locate blood vessels by affecting salivary antihemostatic properties, thus enhancing the possibility of intradermal inoculation of parasites into the mammalian host.

Animals↗