Field tests of repellent M-1960 against leeches.
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Acetanilides↗
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Structural relationships, distribution and biological activities of stemona alkaloids.
Stemona alkaloids represent a unique class of natural products exclusively isolated from the monocotyledonous family Stemonaceae comprising three genera mainly distributed in southeast Asia. Structurally the alkaloids are characterised by a pyrrolo[1,2- a]azepine nucleus usually linked with two carbon chains mostly forming terminal lactone rings. Based on biosynthetic considerations and their various distribution the present review describes 82 Stemona alkaloids grouped into three skeletal types. Due to different carbon chains attached to C-9 of the pyrroloazepine nucleus they were classified into stichoneurine-, protostemonine- and croomine-type alkaloids. The genera Croomia and Stichoneuron only accumulate croomine or stichoneurine derivatives, respectively, whereas the genus Stemona produces all three types of alkaloids. However, species-specific accumulation trends towards certain structural types represent valuable chemosystematic criteria. Bioassays with larvae of Spodoptera littoralis exhibited very high insect toxicity for the roots of Stemona species containing certain protostemonine derivatives, especially didehydrostemofoline, whereas those with dominating stichoneurine or croomine derivatives showed low toxicity but sometimes remarkable repellence due to an accumulation of tuberostemonine. Tuberostemonine also showed effects on the motility of helminth worms and reduced the excitatory transmission at the crayfish neuromuscular junction. Significant antitussive activity was shown for the stereoisomeric neotuberostemonine in guinea-pig after cough induction by citric acid aerosol stimulation. Studies on structure-activity relationship with seven related compounds revealed that the saturated tricyclic pyrrolobenzazepine nucleus of tuberostemonines is the prerequisite for antitussive activity.
Alkaloids↗
Urban malaria vector biology.
One of the main reasons for the set-back in the urban malaria control programme is the peculiar biobehaviour of the principal urban malaria vector Anopheles stephensi. Certain relevant facts such as incrimination as the vector of malaria, sibling or biological species, resting habitat, manlanding behaviour, seasonal prevalence, blood meal analysis, longevity, parity status, daily survival and mortality rates of adults, breeding habitats and vertical distribution of larvae of An. stephensi have been discussed. Determination of density of the vector using various parameters and their relation to malaria endemicity in an urban situation have been reviewed. An. stephensi has become resistant to DDT, HCH, malathion and propoxur in many places in India. Hence for control source reduction, use of predators such as fish and biolarvicides such as Bacillus thuringiensis var israelensis H14 and B. sphaericus, personal protection, i.e., use of appropriate clothing, bed nets, indigenous repellents, etc., information, education and communication (IEC) are to be stressed.
Adult↗
Biological and chemical assays of pyrethroids in cattle dung.
Bioassays were developed in Zimbabwe to measure pyrethroid in cattle dung. These and chemical assays then estimated concentrations in dung from treated oxen and elucidated risks to dung fauna. Laboratory bioassays with adult beetles (Histeridae and Scarabaeinae, including Copris, Digitonthophagus, Onitis and Sisyphus spp.) and muscoid larvae (Musca lusoria Wiedemann) indicated that the LC50 of pyrethroids, as ppm in the wet weight, averaged 0.04 for deltamethrin pour-on, 0.25 for deltamethrin dip, 0.22 for alphacypermthrin pour-on, 0.10 for cyfluthrin pour-on, 0.23 for cypermethrin dip and 0.63 for flumethrin dip. Field bioassays involved artificial dung pats of 800 g, deployed in woodland and inspected after 24 h to record insects dead and alive. Beetles were most abundant in the wet season. Muscoid larvae were less seasonal. The LC50 of insecticides in the field confirmed laboratory indications. Adult Diptera (muscoids and Sgifidae) were not repelled or killed until the deltamethrin concentration reached 10 ppm. Pat dispersal by dung fauna and termites (Microtermes spp.) was halved by deltamethrin at 0.1-1 ppm. Scavenging of dead beetles by ants was greatest with small beetles (< 15 mm long) uncontaminated with insecticide. Dips and pour-ons of deltamethrin on cattle gave residues of about 0.01-0.1 ppm in dung produced in the fortnight after application. About 1.6% of the deltamethrin applied was transferred to dung. Deltamethrin and alphacypermethrin in dung showed no detectable degradation in 64 days. Contamination levels threaten populations of slow-breeding beetles.
Animals↗
Changes in volatile emissions from apple trees and associated response of adult female codling moths over the fruit-growing season.
Odors in the headspace of apple trees were characterized by in situ volatile collections in the orchard. Sixty-two compounds were quantitatively identified with thermal desorption-gas chromatography-mass spectrometry over the complete fruit-growing season. Overall quantities in the headspace of fruit-bearing twig were highest at petal fall and at the beginning of June and August. Interestingly, the latter two periods coincide with the flight maxima of the codling moth, Cydia pomonella, one of the principal pest insects of apple fruit worldwide. Dual-choice bioassays with mated adult female moths in a Y-tube olfactometer showed that the blend of plant-derived volatiles repelled this key pest of apple at petal fall and attracted it from July to mid-August. Single-component analysis indicated that benzaldehyde and butyl acetate might contribute to the observed repellent effect, but the constituents accounting for the attractant effect mid-season remain to be further elucidated. The attractant effect clearly originates from the apple fruit and not from the twig with leaves, as bioassays demonstrated conclusively.
Animals↗
Nonwoven fiber barriers for control of cabbage maggot and onion maggot (Diptera: Anthomyiidae).
We investigated the use of nonwoven fiber barriers for control of cabbage maggot, Delia radicum (L.), and onion maggot, D. antiqua (Meigen). The barriers consist of arrangements of minute fibers loosely intertwined in "web" form. Results from a greenhouse experiment showed that manually applied graphite fibers placed at the base of broccoli plants reduced the number of D. radicum eggs by 64-98%, and that efficacy increased with greater fiber density. Using a melt extrusion process, we devised a method for on-site creation of nonwoven fibers of ethylene vinyl acetate (EVA). In field trials with broccoli and onion plants, EVA fibers significantly reduced the number of cabbage and onion maggots infesting plants. Fiber barriers provided comparable control to standard insecticide applications. The addition of blue, yellow, red, or black pigments, as well as optical brighteners that absorb UV light did not enhance fiber efficacy. Incorporation of capsaicin olfactory repellent to EVA also did not enhance fiber efficacy. Nonwoven fiber barriers may offer an alternative to insecticides for control of cabbage maggot and onion maggot and possibly other insect pests. Additional research is needed to improve the application process and to identify economically feasible and biodegradable compounds for fibers.
Animals↗
Village scale trial of deltamethrin against mosquitoes.
A village scale trial of Deltamethrin (K-othrin), formulated as a 2.5 per cent wettable powder and applied as a residual spray at a dosage of 25 mg/m2, was carried out against both anopheline and culicine mosquitoes, in Vikas Nagar village, Loni PHC, Distt. Ghaziabad (U.P.) in the month of August, 1985. Deltamethrin was found to be effective in reducing the overall vector population for about 10 to 12 weeks. Contact bio-assays also indicated that the insecticide has a residual life of about 12 weeks both on mud and cement plastered surfaces. No mortality was observed in bioassays against airborne effect of the insecticide sprayed on the walls. Twenty-four hour survival rate of the vector population was observed to be below 50 per cent upto 8 to 10 weeks. Observations indicated excito-repellent effect on mosquitoes forcing exodus from treated areas.
Animals↗
Factors that attract and repel mosquitoes in human skin.
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Adult↗
The midline glia of Drosophila: a molecular genetic model for the developmental functions of glia.
The Midline Glia of Drosophila are required for nervous system morphogenesis and midline axon guidance during embryogenesis. In origin, gene expression and function, this lineage is analogous to the floorplate of the vertebrate neural tube. The expression or function of over 50 genes, summarised here, has been linked to the Midline Glia. Like the floorplate, the cells which generate the Midline Glia lineage, the mesectoderm, are determined by the interaction of ectoderm and mesoderm during gastrulation. Determination and differentiation of the Midline Glia involves the Drosophila EGF, Notch and segment polarity signaling pathways, as well as twelve identified transcription factors. The Midline Glia lineage has two phases of cell proliferation and of programmed cell death. During embryogenesis, the EGF receptor pathway signaling and Wrapper protein both function to suppress apoptosis only in those MG which are appropriately positioned to separate and ensheath midline axonal commissures. Apoptosis during metamorphosis is regulated by the insect steroid, Ecdysone. The Midline Glia participate in both the attraction of axonal growth cones towards the midline, as well as repulsion of growth cones from the midline. Midline axon guidance requires the Drosophila orthologs of vertebrate genes expressed in the floorplate, which perform the same function. Genetic and molecular evidence of the interaction of attractive (Netrin) and repellent (Slit) signaling is reviewed and summarised in a model. The Midline Glia participate also in the generation of extracellular matrix and in trophic interactions with axons. Genetic evidence for these functions is reviewed.
Animals↗
The ecological basis of parasite control: ticks and flies.
Tick and fly control programmes have undergone radical review in recent years. Insecticidal control measures are now often seen as a means of reducing target populations to a level sufficiently low for final eradication by biological or ecological techniques, the sterile male method (SIRM) being particularly favoured. As a preliminary, the new range of insecticidal application techniques includes insecticidal tags, bands, blouses, implants and pheromone baits. The final eradication programme could then involve the use of sterile flies or sterile hybrid ticks, for example. Immunization of cattle against ticks, the use of tick-resistant crossbreeds of cattle, tick-repellent grasses and dung burying beetles are among the additional techniques now being actively investigated.
Animals↗
[Repellent effect of the foliage of Melia potent on certain species of Acrididae and not on other related species].
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Animals↗
Blackfly control: what choices after onchocerciasis?
Blackflies are reappearing in areas of West Africa where they used to be controlled with insecticides because they were vectors of the parasite Onchocerca volvulus. Even though they no longer transmit onchocerciasis in these areas they can hinder optimal land use through their biting behaviour. The authors discuss the problems associated with resuming the use of insecticides to control the blackfly and recommend that ground treatment be restricted to areas where it is likely to be effective on a continuing basis. In communities lacking technical and financial resources the only alternative consists of individual protection through the use of repellents or protective clothing.
Africa, Western↗
Mosquito burden and impact on the poor: measures and costs for personal protection in some communities in Thailand.
To gauge the extent of mosquito problems and their impact on local people in Thailand, a simple questionnaire was designed consisting of 6 questions with multiple choices to be answered in 4 different communities in Thailand in 1998 and 1999. Mosquito biting activity was noted often by respondents. They reported that mosquitoes bit both night and day, and that the insects were abundant both in the dry and the rainy seasons. In all 4 communities, a large proportion of the residents used bed nets, mosquito coils, and aerosol sprays for personal protection; vaporizing mats and repellents were used sparingly. The cost of such measures amounted to dollars 4 to dollars 25 per year per household. For most of the residents, this represented a substantial proportion of their income, and was proportionally greater than the average cost of organized mosquito control in developed countries. This suggests that instituting organized local vector control programs would be cheaper and more effective than the individual use of personal protectants that do not reduce mosquito numbers. An assessment of the available products stocked in neighborhood stores and supermarkets for personal protection was made. A variety of insecticidal aerosols, mosquito coils, liquid sprays, vaporizing mats, and vaporizing liquids was stocked. This ample supply of household insecticides lends support to the preferred methods of protection reported by the respondents. The active ingredients in most of the formulations were synthetic pyrethroids, although a few contained dichlorvos, propoxur, and a few other compounds. Mosquito coils, the most preferred products used by the poor, were evaluated for efficacy, and were found to provide a reduction of 72-96% in landing-biting rates in controlled experiments.
Aerosols↗
Response of ants to a deterrent factor(s) produced by the symbiotic bacteria of entomopathogenic nematodes.
The production of an ant-deterrent factor(s) (ADF) by Xenorhabdus nematophila and Photorhabdus luminescens, the symbiotic bacteria of the nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora, respectively, was examined. In addition to an in vivo assay in which bacteria were tested for their ability to produce ADF within insect cadavers (M.E. Baur, H. K. Kaya, and D. R. Strong, Biol. Control 12:231-236, 1998), an in vitro microtiter dish assay was developed to monitor ADF activity produced by bacteria grown in cultures. Using these methods, we show that ADF activity is present in the supernatants of bacterial cultures, is filterable, heat stable, and acid sensitive, and passes through a 10-kDa-pore-size membrane. Thus, ADF appears to be comprised of a small, extracellular, and possibly nonproteinaceous compound(s). The amount of ADF repellency detected depends on the ant species being tested, the sucrose concentration (in vitro assays), and the strain, form, and age of the ADF-producing bacteria. These findings demonstrate that the symbiotic bacteria of some species of entomopathogenic nematodes produce a compound(s) that deters scavengers such as ants and thus could protect nematodes from being eaten during reproduction within insect cadavers.
Animals↗
Chemistry, biological activity, and uses of formamidine pesticides.
The formamidines, a relatively new group of acaricide-insecticides, are novel both in their range of biological activities and in their mode of action, which is presently unknown. This paper is a review of the historical development, properties, structures, uses, and chemistry of this group of pesticides, with particular emphasis on chlordimeform (Galecron or Fundal), N'-4-chloro-o-tolyl-N,N-dimethylformamidine, and amitraz, 1,3=di-(2,4-dimethylphenylimino)-2-methyl-2-azapropane. Their biological activity and uses are defined by their toxicity to spider mites, ticks, and certain insects, and they are particularly effective against juvenile and resistant forms of these organisms. A significant, but poorly understood feature of their field effectiveness is their breadth of toxic action which includes direct lethality, excitant-repellant behavioral effects, and chemosterilization. They are generally of low hazard for nontarget species with the significant exception of predaceous mites. Several aspects of the chemistry of these compounds are considered, including structure--activity relations, synthetic pathways, isomerism and configuration, and their chemical and environmental stability. A significant feature of the metabolism and toxicity of these agents is the possible activation of chlordimeform by N-demethylation in vivo. Strong evidence for this has been presented with the cattle tick, but recent results discussed here suggest that in other species, i.e., mice, German cockroaches or black cutworm eggs, N-demethylation is neither a strong activation nor a detoxication reaction.
Amidines↗
[Summer mastitis: pathogenesis, losses, incidence and prevention].
In cases of summer mastitis, several other bacteria, particularly anaerobes, are isolated in addition to C. pyogenes. The fly Hydrotaea irritants which also causes 'broken heads' in sheep and is therefore referred to as the 'sheep head fly', is universally regarded as the most important vector of summer mastitis. The annual losses caused by summer mastitis are substantial. The incidence of summer mastitis varies annually and monthly. Summer mastitis is particularly observed on sandy soil, less often on peat and hardly ever on clay. This is in accordance with the habitats of Hydrotaea irritans. Several measures to prevent summer mastitis are available to farmers. When fly repellents or agents protecting the teat openings are used, fair results are obtained. Synthetic pyrethroids would appear to offer better prospects, however, because of their long-acting character. Results obtained using C. pyogenes vaccines are disappointing. Long-acting antibiotics offer good prospects in yearlings in the 1-2 year range. Findings reported in the literature show that treatment of dry cows during the dry period, repeated twice at an interval of from three to four weeks, offers the most promising prospects. In view of the small teat openings of calves, fly repellents or agents protecting the teat openings will be most successful.
Animals↗
Soma-germ line competition for lipid phosphate uptake regulates germ cell migration and survival.
Lipid phosphates can act as signaling molecules to influence cell division, apoptosis, and migration. wunen and wunen2 encode Drosophila lipid phosphate phosphohydrolases, integral membrane enzymes that dephosphorylate extracellular lipid phosphates. wun and wun2 act redundantly in somatic tissues to repel migrating germ cells, although the mechanism by which germ cells respond is unclear. Here, we report that wun2 also functions in germ cells, enabling them to perceive the wun/wun2-related signal from the soma. Upon Wun2 expression, cultured insect cells dephosphorylate and internalize exogenously supplied lipid phosphate. We propose that Drosophila germ cell migration and survival are controlled by competition for hydrolysis of a lipid phosphate between germ cells and soma.
Animals↗
Anatomical and chemical defenses of conifer bark against bark beetles and other pests.
Conifers are long-lived organisms, and part of their success is due to their potent defense mechanisms. This review focuses on bark defenses, a front line against organisms trying to reach the nutrient-rich phloem. A major breach of the bark can lead to tree death, as evidenced by the millions of trees killed every year by specialized bark-invading insects. Different defense strategies have arisen in conifer lineages, but the general strategy is one of overlapping constitutive mechanical and chemical defenses overlaid with the capacity to up-regulate additional defenses. The defense strategy incorporates a graded response from 'repel', through 'defend' and 'kill', to 'compartmentalize', depending upon the advance of the invading organism. Using a combination of toxic and polymer chemistry, anatomical structures and their placement, and inducible defenses, conifers have evolved bark defense mechanisms that work against a variety of pests. However, these can be overcome by strategies including aggregation pheromones of bark beetles and introduction of virulent phytopathogens. The defense structures and chemicals in conifer bark are reviewed and questions about their coevolution with bark beetles are discussed.
Animals↗