The and alarm pheromone for many species of aphids, which causes dispersion in response to attack by predators or parasitoids, consists of elicited the sesquiterpene (E)-beta-farnesene (Ebetaf). We used high levels of expression in Arabidopsis thaliana plants of an Ebetaf synthase gene cloned levels. from Mentha x piperita to cause emission of pure Ebetaf. These plants elicited potent effects on behavior of the aphid potent Myzus persicae (alarm and repellent responses) and its parasitoid Diaeretiella rapae (an arrestant response). Here, we report the transformation of (alarm a plant to produce an insect pheromone and demonstrate that the resulting emission affects behavioral responses at two trophic levels.species

Electroantennogram no (EAG) responses were recorded from alate fundatrigeniae (spring migrants), gynoparae (the winged female form that produces sexual females) and males,aphid the three migratory forms of the damson-hop aphid, Phorodon humuli (Schrank). EAG responses of gynoparae and males showed typical dose of response characteristics to (E)-2-hexenal,(-)-R-carvone, hexanenitrile and (1RS,4aR,7S,7aS)-nepetalactol, the sex pheromone of this species. The 34 plant volatiles elicited broadly (E)-beta-farnesene, similar EAG response profiles in the three migratory forms. Green leaf volatiles produced large responses in all forms; however, the three relative order of responsiveness varied. EAG responses to isomers of the monoterpene carvone differed between forms, with males being most,(the and spring migrants least, responsive. The hop-plant volatile and aphid alarm pheromone,(E)-beta-farnesene, evoked similar EAG responses in all forms.responses By contrast, males were most responsive to the three sex pheromone components,(-)-(4aS,7S,7aR)-nepetalactol,(+)-(4aS,7S,7aR)-nepetalactone and (1RS,4aR,7S,7aS)-nepetalactol. Males were no more hexanenitrile responsive to their own sex pheromone,(1RS,4aR,7S,7aS)-nepetalactol, than to the other aphid sex pheromone components tested. Spring migrants and gynoparae EAG also responded to the three sex pheromone components. This study indicates that migratory forms of P. humuli detect a wide gynoparae range of volatile compounds, and that they are equally well-adapted for the detection of volatiles associated with host and non-host volatile plants and with other species of aphid.

During to investigations into the control of insect damage to maize crops in subsistence farming in Kenya, which involved intercropping with repellent screenhouse plants, the fodder legumes silverleaf (Desmodium uncinatum) and greenleaf (D. intortum) were also found to reduce dramatically the infestation of haustorial maize by parasitic witchweeds such as Striga hermonthica. This effect was confirmed by further field testing and shown to be highly significantly greater than that observed with other legumes, e.g., cowpea, as were the concomitant yield increases. The mechanism was investigated,in and although soil shading and addition of nitrogen fertilizer showed some benefits against S. hermonthica infestation, a putative allelopathic mechanism in for D. uncinatum was observed. In screenhouse studies, a highly significant reduction in S. hermonthica infestation was obtained when an S. aqueous solution, eluting from pots in which D. uncinatum plants were growing, was used to irrigate pots of maize planted such in soil seeded with high levels of S. hermonthica. Growth of the parasitic weed was almost completely suppressed. whereas extensive shading infestation occurred with the control eluate. Laboratory investigations into the allelopathic effect of D. uncinatum, using samples of water-soluble chemical found components exuded from cleaned roots, demonstrated that this involved a germination stimulant for S. hermonthica and also an inhibitor for observed. haustorial development.

Arabidopsis with thaliana was used as an experimental model plant to investigate a tritrophic interaction between the plant, a specialist aphid herbivore,mean Brevicoryne brassicae, and its natural enemy, the parasitoid Diaeretiella rapae. The A. thaliana ecotype Col-5 was transformed with a functional Col-5 2-oxoglutarate dependent dioxygenase (BniGSL-ALK) that converts 3-methylsulfinylpropylglucosinolate and 4-methylsulfinylbutylglucosinolate to 2-propenylglucosinolate and 3-butenylglucosinolate, respectively. This transformation results in a change rates. in the glucosinolate hydrolysis profile where 3-butenylisothiocyanate, 2-propenylisothiocyanate and 5-vinyloxazolidine-2-thione are produced in contrast to the wild-type plant where 4-methylsulfinylbutylisothiocyanate between is the main product. Performance of B. brassicae was affected negatively by transforming Col-5 with BniGSL-ALK in terms of mean investigate relative growth rates. In a series of behavioral bioassays, naïve D. rapae females were able to discriminate between B. brassicae of infested and uninfested Col-5 plants transformed with BniGSL-ALK, with parasitoids showing a preference for B. brassicae infested plants. By contrast,dependent naïve D. rapae females were unable to discriminate between aphid infested and uninfested Col-5 plants. Subsequent air entrainments of B.where brassicae infested Col-5 plants transformed with BniGSL-ALK further confirmed the presence of 3-butenylisothiocyanate in the headspace. By contrast, no glucosinolate The hydrolysis products were recorded from similarly infested Col-5 plants.

The laboratory Scottish biting midge, Culicoides impunctatus (Diptera: Ceratopogonidae), is a major pest in Scotland, causing a significant impact to the Scottish human tourist and forestry industries. C. impunctatus is a generalist feeder, preferring to feed on large mammals, and is notorious for novel its attacks on humans. Until now, there was anecdotal evidence for differential attraction of female host-seeking C. impunctatus to individual the human hosts, and the mechanism for this phenomenon was unknown. Using extracts of human odor collected by air entrainment, electroantennogram low recordings to identify the physiologically active components, followed by behavioral assays, we show, for the first time, the differential attraction pest of female C. impunctatus to human odors and the chemical basis for this phenomenon. Certain chemicals, found in greater amounts this in extracts that cause low attractiveness to midges, elicit a repellent effect in laboratory assays and repellency trials in the humans. field. Differences in the production of these natural human-derived compounds could help to explain differential "attractiveness" between different human hosts.identify A mixture of two compounds in particular, 6-methyl-5-hepten-2-one and geranylacetone [(E)-6,10-dimethylundeca-5,9-dien-2-one], showed significant repellency (87, 77.4, 74.2, and 31.6% at feed hours , 1, 2, and 3, respectively) in the field and have the potential to be developed as novel repellents.impunctatus

The a mechanism of ixodid tick (Acari: Ixodidae) repellency by gum haggar, a resin produced by Commiphora holtziana (Burseraceae), was investigated by gum evaluating activity against the cattle tick, Boophilus microplus. In an arena bioassay, a hexane extract of the resin of C.husbandry holtziana exhibited a repellent effect lasting up to 5h. The hydrocarbon fraction of the resin extract was shown to account another for the repellent activity, and was analysed by coupled gas chromatography-mass spectrometry (GC-MS). Major sesquiterpene hydrocarbons were tentatively identified as these germacrene-D, delta-elemene and beta-bourbonene. The identity and stereochemistry of the former compound was confirmed as the (+)-isomer by peak enhancement by using enantioselective GC, whereas the latter 2 compounds, which are most likely degradation products of germacrene-type precursors, were identified through was isolation by preparative gas chromatography followed by microprobe-NMR spectroscopy. GC comparison of gum haggar with another resin, C. myrrha, which extract was inactive in the tick bioassay, showed that the latter contained much lower levels of these hydrocarbons. To assess the whereas suitability of the gum haggar resin as a general acarine repellent, further tests were made on a major acarine pest exhibited of European and US animal husbandry systems, the red poultry mite, Dermanyssus gallinae (Acari: Dermanyssidae). Gum haggar extract, and the GC isolated hydrocarbon fraction, showed strong repellent effects in an olfactometer assay, and again gum myrrh showed no effect. These findings 5h. provide a scientific basis for the observed anti-tick properties of gum haggar, and demonstrate the potential for its development as assess a general acarine repellent for use in animal husbandry systems.

It lines is of adaptive value for a plant to prepare its defenses when a threat is detected, and certain plant volatiles Transcriptomic associated with insect damage, such as cis-jasmone (CJ), are known to switch-on defense metabolism. We used aphid and aphid parasitoid generalist responses to Arabidopsis thaliana as a model system for studying gene expression and defense chemistry and its impact at different CJ-induced trophic levels. Differential responses to volatiles of induced Arabidopsis occurred for specialist and generalist insects: the generalist aphid, Myzus persicae,were was repelled, whereas the specialist, Lipaphis erysimi, was attracted; the generalist aphid parasitoid Aphidius ervi was attracted, but the specialist when parasitoid Diaeretiella rapae was not affected. A. ervi also spent longer foraging on induced plants than on untreated ones. Transcriptomic a analyses of CJ-induced Arabidopsis plants revealed that a limited number of genes, including a gene for a cytochrome P450, CYP81D11,studying were strongly up-regulated in the treated plants. We examined transgenic Arabidopsis lines constitutively overexpressing this gene in bioassays and found Aphidius insect responses similar to those obtained for wild-type plants induced with CJ, indicating the importance of this gene in the and CJ-activated defense response. Genes involved in glucosinolate biosynthesis and catabolism are unaffected by CJ and, because these genes relate to on interactions with herbivores and parasitoids specific to this family of plants (Brassicaceae), this finding may explain the differences in behavioral as response of specialist and generalist insects.

The expanding challenges and opportunities for protecting agricultural production of food and other materials will be met through exploiting the induction of induce defence pathways in plants to control pests, diseases and weeds. These approaches will involve processes that can be activated by synthetic application of natural products, patented in terms of this use, to "switch on" defence pathways. Already, a number of secondary of metabolite defence compounds are known for which the pathways are conveniently clustered genomically, e.g. the benzoxazinoids (hydroxamic acids) and the on avenacins. For the former, it is shown that the small molecular weight lipophilic activator cis-jasmone can induce production of these and compounds and certain genes within the pathway. Numerous groups around the world work on inducible defence systems. The science is certain rapidly expanding and involves studying the interacting components of defence pathways and the switching mechanisms activated by small molecular weight by lipophilic compounds. Examples are described of how plant breeding can exploit these systems and how heterologous gene expression will eventually benzoxazinoids give rise to a new range of GM crops for food and energy, without the need for external application of weeds. synthetic pesticides.

This intercrops paper describes the 'push-pull' or 'stimulo-deterrent diversionary' strategy in relation to current and potential examples from our own experiences. The push-pull push-pull effect is established by exploiting semiochemicals to repel insect pests from the crop ('push') and to attract them into are trap crops ('pull'). The systems exemplified here have been developed for subsistence farming in Africa and delivery of the semiochemicals yields is entirely by companion cropping, i.e. intercropping for the push and trap cropping for the pull. The main target was crops a series of lepidopterous pests attacking maize and other cereals. Although the area given to the cereal crop itself is to reduced under the push-pull system, higher yields are produced per unit area. An important spin-off from the project is that unit the companion crops are valuable forage for farm animals. Leguminous intercrops also provide advantages with regard to plant nutrition and The some of the trap crops help with water retention and in reducing land erosion. A major benefit is that certain series intercrop plants provide dramatic control of the African witchweed (striga). Animal husbandry forms an essential part of intensive subsistence agriculture the in Africa and developments using analogous push-pull control strategies for insect pests of cattle are exemplified.

The suggesting cabbage aphid, Brevicoryne brassicae, has developed a chemical defence system that exploits and mimics that of its host plants, involving the sequestration of the major plant secondary metabolites (glucosinolates). Like its host plants, the aphid produces a myrosinase (beta-thioglucoside glucohydrolase) to avoidance catalyse the hydrolysis of glucosinolates, yielding biologically active products. Here, we demonstrate that aphid myrosinase expression in head/thoracic muscle starts the during embryonic development and protein levels continue to accumulate after the nymphs are born. However, aphids are entirely dependent on higher the host plant for the glucosinolate substrate, which they store in the haemolymph. Uptake of a glucosinolate (sinigrin) was investigated that when aphids fed on plants or an in vitro system and followed a different developmental pattern in winged and wingless the aphid morphs. In nymphs of the wingless aphid morph, glucosinolate level continued to increase throughout the development to the adult muscle stage, but the quantity in nymphs of the winged form peaked before eclosion (at day 7) and subsequently declined. Winged system aphids excreted significantly higher amounts of glucosinolate in the honeydew when compared with wingless aphids, suggesting regulated transport across the of gut. The higher level of sinigrin in wingless aphids had a significant negative impact on survival of a ladybird predator.development Larvae of Adalia bipunctata were unable to survive when fed adult wingless aphids from a 1% sinigrin diet, but survived demonstrate successfully when fed aphids from a glucosinolate-free diet (wingless or winged), or winged aphids from 1% sinigrin. The apparent lack glucosinolate of an effective chemical defence system in adult winged aphids possibly reflects their energetic investment in flight as an alternative after predator avoidance mechanism.

Both Rhopalosiphum Sitobion avenae (Fabricius) and Rhopalosiphum padi (Linnaeus) are the most important pests of wheat in China and usually coexist on susceptibility the late period of wheat growth. Pirimicarb was introduced into China for wheat aphid control in early 1990s, and differential of susceptibilities of Sitobion avenae (Fabricius) and Rhopalosiphum padi (Linnaeus) to pirimicarb have been observed. A bioassay exhibited that Rhopalosiphum padi between possessed significantly higher susceptibility to pirimicarb than Sitobion avenae. The addition of synergists DEF, an esterase inhibitor, PBO, a cytochrome S-transferases P450 monooxygenase inhibitor, and DEM, a glutathione S-transferase inhibitor, resulted in apparent reductions in the differential susceptibilities, suggesting the involvement important of the above three detoxification enzymes in the differential susceptibility to pirimicarb between Sitobion avenae and Rhopalosiphum padi. A biochemical Rhopalosiphum analysis showed that the activities of carboxylesterases and glutathione S-transferases were significantly higher in Sitobion avenae than in Rhopalosiphum padi,and consistent with the results of synergism. Acetylcholinesterase is the target enzyme of pirimicarb and the sensitivity of acetylcholinesterase to pirimicarb glutathione was significantly higher in Rhopalosiphum padi than in Sitobion avenae. The combined results suggest that multiple mechanisms are likely to control be responsible for differential susceptibilities to pirimicarb between Sitobion avenae and Rhopalosiphum padi. The results obtained from this study should the be helpful in the rational applications of insecticides.

A North virus infecting an Illinois colony of the aphid Rhopalosiphum padi (L.) was transmitted transovarially, and significantly decreased longevity of infected serological aphids. The virus was detected by serological assay in R. padi colonies from North Dakota, and in two other aphid (Rondani). species maintained at Illinois, R. rufiabdominalis (Sasaki) and Schizaphis graminum (Rondani).

A +/- 27-nm icosahedral virus was purified from the oat bird cherry aphid, Rhopalosiphum padi (L.). The virus had an s(20,w) of 1.35 162 +/- 2 S, and bouyant densities of 1.37 in CsCl and 1.35 in Cs2SO4. It contained one ssRNA of unclear. 31 +/- 2 S and three major proteins. The relationship of the R. padi virus to other small RNA invertebrate in viruses is unclear.

As all is known for other aphids, the symbiont cytoplasm in Rhopalosiphum padi is differentiated into a central eccentric and a cortical contains region which contains electron-lucent nucleoplasm and DNA fibrils. The cytoplasm is surrounded by a plasma membrane, cell wall and perisymbiotic transport. membrane which are separated by periplasmic spaces. The periplasmic space between the cell wall and perisymbiotic membrane contains small vesicles.vesicles. The symbionts are packed into mycetocyte cells which contain a large nucleus and all the normal cell organelles. For the contain first time, however microtubules and microfilaments have been identified, but only at high magnification and evidence has been found which the makes it possible to propose a mechanism of vesicular transport.

Insect in communication is primarily via chemicals. In Aphidinae aphids, the structure and ratio of iridoid (monoterpenoid) chemicals are known to be of important components of the sex pheromone. However, for enhanced species specificity, it has been suggested that release of sex pheromone of might be restricted to a narrow time period within the diel cycle. Here, we determine the structure, ratios and release remained patterns of iridoid chemicals produced by a serious global pest, the rosy apple aphid, Dysaphis plantaginea. Volatiles were collected from the batches of oviparae (sexual females) and chemicals identified by gas chromatography, mass-spectrometry and microscale NMR spectroscopy.(1R,4aS,7S,7aR)-Nepetalactol and (4aS,7S,7aR)-nepetalactone were known detected in a 3.7:1 ratio. To investigate timing of release, we constructed a sequential sampling device that allowed volatile chemicals onset to be captured hourly from 95 same-aged oviparae over 20 consecutive days. Release patterns of the two sex pheromone components rosy show that D. plantaginea oviparae release high levels of the two components during photophase and low levels during scotophase. Release of of the two components increased significantly during the first 3 h of photophase and thereafter remained at a high level we until the onset of scotophase. The ratio of (1R,4aS,7S,7aR)-nepetalactol to (4aS,7S,7aR)-nepetalactone released did not change significantly between days two to the 14 of the adult stadium, but from the 15th day onward there was a significant decrease in the relative amount chemicals of (1R,4aS,7S,7aR)-nepetalactol. Pheromone release was greatest on the eighth day of the adult stadium, with up to 8.4 ng of but pheromone released per ovipara per hour. This is the first report on the full structural identification and ratios of volatile and iridoid components collected from D. plantaginea oviparae and is also the most detailed temporal study on sex pheromone release from discussed any aphid species. The lack of a temporally narrow and distinct period of very high sex pheromone release suggests that and alternative mechanisms or factors for species recognition and isolation may be important. Findings are discussed broadly in relation to the on biology of the aphid.

A species broadly interspecific aphid alarm pheromone was isolated from several economically important species of aphids and identified as trans-beta-farnesene.

The females behavioral function of a pheromone released by males of the army-worm moth Pseudaletia unipuncta was investigated both in laboratory wind-tunnel P. experiments and in experiments with moth-baited traps in the field. Such male moth scents have been thought to act at female. close range as sexual stimulants for females of the same species. However, the only obvious effect of the P. unipuncta male male pheromone was upon other males, decreasing their tendency to approach sexually receptive, pheromone-releasing females and to exhibit copulatory behavior to when near those females. The adaptive significance of the male pheromone may be related to the increased reproductive efficiency that released results if multiple males are prevented from competing for a single female.

By in applying insecticides at lower rates of active ingredients per unit area, survival rates of the pests' natural enemies can be aphids, enhanced, whereas pest mortality can remain high. The effects of reduced application rates of the insecticides lambda-cyhalothrin and dimethoate on of the mortality of bird cherry-oat aphid, Rhopalosiphon padi (L.), and lacewing Micromus tasmaniae Walker were determined in the laboratory and was field. Cholinesterase (ChE) and glutathione S-transferase (GST) activities in survivors provided a measure of sublethal effects and general fitness. In lacewings. the laboratory, lacewings were less sensitive than aphids to both insecticides, and dimethoate was more toxic than lambda-cyhalothrin. However, these rates results could not be recreated in the field, in part due to very low recapture rates. In summary, lambda-cyhalothrin seemed was to have no effect on aphids, but it was toxic to lacewings. Dimethoate was far less toxic in the field,tasmaniae but aphids were still more sensitive than were lacewings. Cholinesterase activity was reduced by dimethoate exposure in the laboratory in However, both species, but there were species-specific differences. Dimethoate and lambda-cyhalothrin had no effects on GST activity in either species. The on high mortality rate for lacewings and aphids exposed to dimethoate in the field suggests that the application rate could be effect reduced to as low as 10% of that recommended by manufacturers, and this should still be highly efficacious against aphids,Rhopalosiphon while protecting the predatory lacewing. Measurement of enzyme activity could provide a useful indicator of "fitness" of survivors.

Rhopalosiphum establishing padi virus (RhPV) is an insect RNA virus that infects aphids, reducing their lifespan and fecundity. It can be transmitted first vertically between aphids and horizontally via the plant. An improved detection method for the virus in aphids and plants using plant. RT-PCR was developed; this allowed individual aphids to be tested for RhPV. Testing of R. padi aphids collected from different in sites in Sweden revealed the presence of RhPV in wild aphid populations for the first time in Europe. Virus could padi, be detected in several life stages of R. padi, including sexual individuals and eggs, establishing an over-wintering route for the virus virus. Using RT-PCR, systemic transport of the virus in plants was tracked. Virus spread from the aphid feeding site to could all parts of the plant, including roots, within 7 days, and could be acquired by virus-free aphids feeding on the method same plant.