Repellent Effects of Methyl Anthranilate on Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae) in Soil Bioassays

Methyl anthranilate (MA), a compound in maize roots that is repellent to western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) was tested in behavioral bioassays in a soil environment. MA prevented larvae from locating roots of a maize seedling, and the repellency strengthened with increasing rates of MA. In a simple push– pull strategy between an MA-treated seedling and an untreated seedling, granules containing 0.1 mg/g MA pushed larvae to the untreated seedling. This push effect increased with dose, with 90% repellency observed for the highest dose tested (100 mg/g). Chemical analysis showed that MA concentrations remained high for 4 wk in dry, sterilized or unsterilized soil, but declined rapidly in moist soil. After 7 d, 50% less MA was recovered in moist, sterilized soil than in dry soil, and only a trace of MA remained in unsterilized moist soil, suggesting that both moisture and microbial activity contributed to the loss of MA. Various (MA) carrier granules were tested in bioassays after aging in moist soil. After 1 d, all of the MA granules were repellent at the 10 mg/g rate and clay granules were also effective at 1 mg/g. After 1 wk, only molecular sieve granules elicited repellency, but that activity disappeared after 2 wk. These results demonstrate that MA is repellent to western corn rootworm larvae in the soil environment and may have potential as a rootworm treatment if formulations can be developed that protect the material from decomposition in the soil

Sugar preferences of western corn rootworm larvae in a feeding stimulant blend

Feeding behaviour, feeding intensity and staying behaviour of neonate western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) were evaluated in response to synthetic feeding stimulant blends to determine larval preferences among the three maize root sugars (glucose, fructose and sucrose) in the active blend and to determine whether any single sugar can substitute for the 3-sugar combination in a feeding stimulant blend. These experiments demonstrated the strong affinity that western corn rootworm larvae have for the natural sugars found in maize roots and also showed that sucrose is the most preferred of the three primary maize root sugars. The blend containing sucrose at 30 mg/ml elicited feeding that was not significantly different than the natural glucose:fructose:sucrose blend. In subtraction bioassays, removal of sucrose from the blend resulted in significantly fewer larvae feeding. When the three-sugar blend was substituted with one of the number of various mono-, di-or trisaccharides, fewer larvae fed on all of the treatments compared to the blend with sucrose, except for the blend with maltose. In feeding choice tests, larvae preferred a blend containing sucrose over blends with either glucose or fructose, but larvae chose equally between a blend with sucrose and a blend containing the three-sugar mixture found in maize roots. Based on these results, a feeding stimulant blend with glucose (30 mg/ml), fructose (4 mg/ml) and sucrose (4 mg/ml) elicits the strongest feeding response, but sucrose alone, in amounts equivalent to the total maize root sugar concentration (30 mg/ml), could serve as a substitute for the 3-sugar mixture in a synthetic feeding stimulant blend

Identification of mosquito repellent odours from Ocimum forskolei

<p>Abstract</p> <p>Background</p> <p>Native mosquito repellent plants have a good potential for integrated mosquito control in local settings. <it>Ocimum forskolei</it>, Lamiaceae, is used in Eritrea as a spatial mosquito repellent inside houses, either through crushing fresh plants or burning dry plants. We verified whether active repellent compounds could be identified using gas-chromatography coupled electroantennogram recordings (GC-EAD) with headspace extracts of crushed plants.</p> <p>Results</p> <p>EAD active compounds included (R)-(-)-linalool, (S)-(+)-1-octen-3-ol, trans-caryophyllene, naphthalene, methyl salicylate, (R)-(-)-α-copaene, methyl cinnamate and (E)-ocimene. Of these compounds (R)-(-)-linalool, methyl cinnamate and methyl salicylate reduced landing of female <it>Aedes aegypti </it>on human skin-odor baited tubes. The latter two are novel mosquito repellent compounds.</p> <p>Conclusions</p> <p>The identification of mosquito repellent compounds contributes to deciphering the mechanisms underlying repulsion, supporting the rational design of novel repellents. The three mosquito repellent compounds identified in this study are structurally dissimilar, which may indicate involvement of different sensory neurons in repulsion. Repulsion may well be enhanced through combining different repellent plants (or their synthetic mimics), and can be a locally sustainable part in mosquito control efforts.</p

Lateralization in the Invertebrate Brain: Left-Right Asymmetry of Olfaction in Bumble Bee, Bombus terrestris

Brain and behavioural lateralization at the population level has been recently hypothesized to have evolved under social selective pressures as a strategy to optimize coordination among asymmetrical individuals. Evidence for this hypothesis have been collected in Hymenoptera: eusocial honey bees showed olfactory lateralization at the population level, whereas solitary mason bees only showed individual-level olfactory lateralization. Here we investigated lateralization of odour detection and learning in the bumble bee, Bombus terrestris L., an annual eusocial species of Hymenoptera. By training bumble bees on the proboscis extension reflex paradigm with only one antenna in use, we provided the very first evidence of asymmetrical performance favouring the right antenna in responding to learned odours in this species. Electroantennographic responses did not reveal significant antennal asymmetries in odour detection, whereas morphological counting of olfactory sensilla showed a predominance in the number of olfactory sensilla trichodea type A in the right antenna. The occurrence of a population level asymmetry in olfactory learning of bumble bee provides new information on the relationship between social behaviour and the evolution of population-level asymmetries in animals

Biosynthesis of Unusual Moth Pheromone Components Involves Two Different Pathways in the Navel Orangeworm, Amyelois transitella

The sex pheromone of the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), consists of two different types of components, one type including (11Z,13Z)-11,13-hexadecadienal (11Z,13Z-16:Ald) with a terminal functional group containing oxygen, similar to the majority of moth pheromones reported, and another type including the unusual long-chain pentaenes, (3Z,6Z,9Z,12Z,15Z)-3,6,9,12,15-tricosapentaene (3Z,6Z,9Z,12Z,15Z-23:H) and (3Z,6Z,9Z,12Z,15Z)- 3,6,9,12,15-pentacosapentaene (3Z,6Z,9Z,12Z,15Z-25:H). After decapitation of females, the titer of 11Z,13Z-16:Ald in the pheromone gland decreased significantly, whereas the titer of the pentaenes remained unchanged. Injection of a pheromone biosynthesis activating peptide (PBAN) into the abdomens of decapitated females restored the titer of 11Z,13Z-16:Ald and even increased it above that in intact females, whereas the titer of the pentaenes in the pheromone gland was not affected by PBAN injection. In addition to common fatty acids, two likely precursors of 11Z,13Z-16:Ald, i.e., (Z)-11-hexadecenoic and (11Z,13Z)-11,13-hexadecadienoic acid, as well as traces of (Z)-6-hexadecenoic acid, were found in gland extracts. In addition, pheromone gland lipids contained (5Z,8Z,11Z,14Z,17Z)-5,8,11,14,17-icosapentaenoic acid, which also was found in extracts of the rest of the abdomen. Deuterium-labeled fatty acids, (16,16,16-D3)-hexadecanoic acid and (Z)-[13,13,14,14,15,15,16,16,16-D9]-11-hexadecenoic acid, were incorporated into 11Z,13Z-16:Ald after topical application to the sex pheromone gland coupled with abdominal injection of PBAN. Deuterium label was incorporated into the C23 and C25 pentaenes after injection of (9Z,12Z,15Z)- [17,17,18,18,18-D5]-9,12,15-octadecatrienoic acid into 1–2 d old female pupae. These labeling results, in conjunction with the composition of fatty acid intermediates found in pheromone gland extracts, support different pathways leading to the two pheromone components. 11Z,13Z-16:Ald is probably produced in the pheromone gland by Δ11 desaturation of palmitic acid to 11Z-16:Acid followed by a second desaturation to form 11Z,13Z-16:Acid and subsequent reduction and oxidation. The production of 3Z,6Z,9Z,12Z,15Z-23:H and 3Z,6Z,9Z,12Z,15Z-25:H may take place outside the pheromone gland, and appears to start from linolenic acid, which is elongated and desaturated to form (5Z,8Z,11Z,14Z,17Z)-5,8,11,14,17-icosapentaenoic acid, followed by two or three further elongation steps and finally reductive decarboxylation

Identification of a Sex Pheromone Produced by Sternal Glands in Females of the Caddisfly Molanna angustata Curtis

In the caddisfly Molanna angustata, females produce a sex pheromone in glands with openings on the fifth sternite. Gas chromatographic analyses of pheromone gland extracts with electroantennographic detection revealed four major compounds that stimulated male antennae. These compounds were identified by means of gas chromatography–mass spectrometry and enantioselective gas chromatography as heptan-2-one, (S)-heptan-2-ol, nonan-2-one, and (S)-nonan-2-ol in the approximate ratio of 1:1:4:10, respectively. Field tests showed that the mixture of the two alcohols was attractive to males whereas addition of the corresponding ketones reduced trap catches. The sex pheromone of M. angustata, a species in the family Molannidae within the suborder Integripalpia, is similar to the pheromones or pheromone-like compounds previously reported from six other trichopteran families, including members of the basal suborder Annulipalpia. This suggests that minimal evolutionary change of the pheromone chemistry has taken place within the leptoceroid branch of integripalpian Trichoptera compared to the ancestral character state

Benzoxazinoids in Root Exudates of Maize Attract Pseudomonas putida to the Rhizosphere

Benzoxazinoids, such as 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA), are secondary metabolites in grasses. In addition to their function in plant defence against pests and diseases above-ground, benzoxazinoids (BXs) have also been implicated in defence below-ground, where they can exert allelochemical or antimicrobial activities. We have studied the impact of BXs on the interaction between maize and Pseudomonas putida KT2440, a competitive coloniser of the maize rhizosphere with plant-beneficial traits. Chromatographic analyses revealed that DIMBOA is the main BX compound in root exudates of maize. In vitro analysis of DIMBOA stability indicated that KT2440 tolerance of DIMBOA is based on metabolism-dependent breakdown of this BX compound. Transcriptome analysis of DIMBOA-exposed P. putida identified increased transcription of genes controlling benzoate catabolism and chemotaxis. Chemotaxis assays confirmed motility of P. putida towards DIMBOA. Moreover, colonisation essays in soil with Green Fluorescent Protein (GFP)-expressing P. putida showed that DIMBOA-producing roots of wild-type maize attract significantly higher numbers of P. putida cells than roots of the DIMBOA-deficient bx1 mutant. Our results demonstrate a central role for DIMBOA as a below-ground semiochemical for recruitment of plant-beneficial rhizobacteria during the relatively young and vulnerable growth stages of maize

Odor stimuli: not just chemical identity

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