Host Plant Odours Research Articles

Influence of pre‐emergence experience on response to host and host plant odours in the larval parasitoid Eupelmus vuilleti

AbstractThe response to different host and plant species odours was investigated in Eupelmus vuilleti (Crw). This hymenopteran is a solitary ectoparasitoid of several species of bruchids developing inside Leguminosae seeds. The locomotor behaviour of females reared on Bruchidius atrolineatus (Pic) larvae developing in Vigna unguiculata (Walp) seeds was analysed using a tubular olfactometer. Females showed a specific sensitivity to the semiochemicals emanating from the host and the seed species on which they had developed. Odours from V. unguiculata seeds were attractive to the parasitoid and stimulated their locomotor activity. Odours from Vigna radiata (Wil) seeds had no effect on the locomotor behaviour. Odours from B. atrolineatus larvae were attractive to the females whereas odours from Callosobruchus maculatus (Fab), another bruchid species, had no effect. By isolating the females from the seed and the host at different developmental stages, we found that the specific sensitivity observed resulted from an early adult learning. This learning which occurs before the emergence from the seed while the imago is in the larval chamber of its host is dependent on contact with the seed and the host larval remains.

Flight behaviour of the black bean aphid, Aphis fabae, and the cabbage aphid, Brevicoryne brassicae, in host and non‐host plant odour

Abstract. Walking alate virginoparae of Brevicoryne brassicae (L.) and Aphis fabae Scopoli were presented with odours of steam‐distilled extracts of the non‐host plants summer savoury (Satureja hortensis L.) and tansy (Tanacetum vulgare L.) in an olfactometer. No effects of the extracts were observed on B. brassicae. However, A.fabae were repelled by summer savoury and tansy odour; both extracts also masked an attractant response to bean (host plant) odour. In a flight chamber, air permeated with odour from host or non‐host plants was blown over flying alates of both species, with a green, plant‐mimicking target presented once a minute. The incidence of targeted (host‐responsive) flight of B.brassicae was not affected by odour from a growing host plant (Brassica oleoracea) or a non‐host plant tansy. Host plant (Vicia faba) odour did not affect the initial rate of climb or the incidence of targeted flight of A.fabae, but when the bean odour was alternated with odour from non‐host tansy plants a greater number of targeted flights occurred in the host plant odour. The volatile extracts of tansy and summer savoury were also presented to flying A.fabae. Aphids flying in air permeated with tansy odour at 450g plant equivalents initiated fewer targeted flights than when flying in clean air. However, no differences in flight behaviour were observed with summer savoury extract. In a horizontal wind tunnel the tansy extract at 90 g plant equivalents blown across the surface of yellow targets reduced the numbers of alate A.fabae landing. The results indicate that plant odours can affect flight and landing of aphids.

Specificity of sex pheromones, the role of host plant odour in the olfactory attraction of males, and mate recognition in the aphid Cryptomyzus

Abstract. Choice tests in an olfactometer showed that males of the aphid Cryptomyzus galeopsidis spent more time in the odour of conspecific females than of a sibling species or a more distantly related Cryptomyzus species, which all co‐occur on red currant. Analysis of the pheromone‐emissions of females showed the presence of a nepetalactol and a nepetalactone, two known aphid sex pheromone components. However, no interspecific difference in the ratio of the components (c. 30:1) was found, and this ratio did not change as the females aged. Males were only slightly attracted by a synthetic 30:1 mixture of these two components, and in a choice test preferreď the odour of conspecific females. The sex pheromone of Cryptomyzus spp. must thus consist of more than two components, the first time this has been reported for aphids. Host plant odour did not attract males or enhance the activity of the pheromone.

Response of single antennal neurons of female cabbage loopers to behaviorally active attractants

The response to biologically significant odor signals in insects is dependent on a well-developed olfactory system. For most moths, successful mate location depends ultimately on a coupling between female-emitted sex pheromone components and male antennal receptor cells [I]. The reception and processing of pheromones by male moth sensory pathways have been better elucidated than host-plant odor reception by female insects Among the possible reasons for this discrepancy is the fact that female behavioral responses have not been intensively investigated, and there appear to be many possible active combinations of components from these complex mixtures [2, 31. A better understanding of the relationship between host-plant odors and their effects on the peripheral olfactory receptors of females is necessary inasmuch as volatile chemicals emitted by plants are often crucial in enabling female insects to locate suit-

Reactions of adult female parasitoids, particularly Aphidius rhopalosiphi, to volatile chemical cues from the host plants of their aphid prey

Abstract. In Y‐tube olfactometer tests, Aphidius ervi Hal., Trioxyssp., Praon sp., Aphelinus flavus (Nees), Lysiphlebus fabarum (Marsh.) and Aphidius rophalosiphi De Stef. responded positively to the odour of the plant on which aphid mummies containing them had been collected. The response to host plant odour was greater than the response to the odour of host aphids, their honeydew or a combination of the two. The strongest response was to a combination of plant and host aphids. A. rhopalosiphi showed a strong positive response to three wheat volatiles (cis‐3‐hexenyl acetate, cis‐3‐hexen‐1‐ol and trans‐2‐hexenal) as well as to indole‐3‐acetaldehyde (a breakdown product of tryptophan in aphid honeydew). In both olfactometer tests with odours and choice trials with whole plants, newly emerged A. rhopalosiphidistinguished and preferred the variety of wheat on which their development had occurred to other wheat varieties.

Electroantennogram responses of the cabbage seed weevil,Ceutorhynchus assimilis, to oilseed rape,Brassica napus ssp.Oleifera, volatiles

Electroantennograms (EAGs) were recorded from male and female cabbage seed weevils (Ceutorhynchus assimilis Payk.) in response to volatiles isolated and identified from the odor of oilseed rape (Brassica napus ssp.oleifera DC. cv. Ariana). Relatively large EAGs were obtained on stimulation with volatiles produced by the oilseed rape crop at the time when seed weevils were actively searching for host plants. Artificial rape odor without certain key volatile compounds was in most cases significantly less stimulatory than odor containing these volatiles. There were significant differences in the EAG response of the sexes ofC. assimilis to the green leaf volatiles of oilseed rape and several terpenes present in rape flower odor. The importance of the qualitative and quantitative composition of host-plant odor in host location byC. assimilis is discussed.

Floral volatiles ofTanacetum vulgare L. attractive toLobesia botrana den. et schiff. females

The European grapevine moth (EGVM),Lobesia botrana, is a major pest of grapes in Europe. Females are attracted to a nonhost plant: tansy (Tanacetum vulgare L.), which is a common weed in Slovakian vineyards. A steam distillate extract of tansy flowers was analyzed by means of a GC-EAG technique to screen constituents detected by the olfactory receptors of EGVM females. From more than 200 GC peaks, nine peaks corresponding to monoterpenoids released an EAG response in more than 70% of the females (N=15):p-cymene,d-limonene,α-thujene,α-thujone,β-thujone, thujyl alcohol, terpinene-4-ol, (Z)-verbenol, and piperitone. The steam distillate of tansy as well as a synthetic blend of identified compounds released consistent attraction in a field cage. The use of nonhost plants and host plant odors in integrated pest management is discussed.

Host finding and discrimination inDiglyphus isaea, a parasitoid of the chrysanthemum leaf miner,Chromatomyia syngenesiae

Naive and experienced Diglyphus isaea were attracted by host plant odours of lettuce and chrysanthemum to search and probe on infested and uninfested leaves. A slight preference was shown for leaves infested with Chromatomyia syngenesiae. At close range, visual stimuli were unnecessary for oviposition and host‐feeding. Contact with uninfested lettuce and chrysanthemum elicited searching and probing behaviour whereas host frass did not. Host larval movement appeared to aid host detection at close range. The number of ovipositor probes increased with proximity to live hosts but not for stationary, dead hosts. Dead hosts were frequently walked over or missed when D. isaea passed within 0.5 cm of the stationary larvae. Dead hosts were also rejected for oviposition but not for host feeding. Both naive and experienced females discriminated between healthy hosts and those which had been attacked by conspecifics or encountered previously.

Behavioral and electrophysiological responses of Aphids to host and nonhost plant volatiles

Alate and apterous virginoparae ofAphis fabae Scop, and alate virginoparae ofBrevicoryne brassicae (L.), walking in a linear track olfactometer, were attracted by odor from leaves of their host plants.A. fabae responded to odor from undamaged but not damaged bean leaves. Gynoparae (autumn migrants) ofA. fabae, however, did not respond to their host plant (spindle,Euonymus europaeus) odor. Odors of certain nonhost plants masked the attractiveness of the host plant leaves, but tansy (Tanacetum vulgare) and summer savory (Satureja hortensis) volatiles repelledB. brassicae andA. fabae, respectively. 3-Butenyl isothiocyanate attractedB. brassicae andLipaphis erysimi (Kalt.), the latter species being more sensitive in both behavioral and electrophysiological studies. Isothiocyanate receptors were found on the antennae ofA. fabae, which was repelled by these compounds, 4-pentenyl isothiocyanate being the most active.

Sensory biology of Chilo spp. with specific reference to C. partellus

This paper reports observations made on the sensory biology of Chilo partellus larvae and adults. The larval and adult antennae of this insect have hygro/thermosensitive sensilla equipped with receptor cells sensitive to minute changes in temperature. Inputs through those cells may partly be responsible for the light evasive and other light/temperature-dependent behaviour patterns. The grooved basiconic sensilla especially those found on the male antennae are sensitive to the female sex pheromone components of C. partellus. Host-plant odours are most likely perceived by one or two of the other antennal olfactory sensilla, namely the smooth-surfaced basiconica and coeloconica sensilla. Chilo partellus moths have a limited number of gustatory sensilla on the tarsi, ovipositor, antennae and the proboscis. Electrophysiological bioassays done on the ovipositor and tarsal sensilla are discussed. Similar tests on the larval maxillary styloconica sensilla showed that the lateral and medial sensilla differed in their sensitivity. Their taste receptor cells can detect differences between saps from susceptible and resistant host-plants.

Attraction of the grasshopper, Melanoplus sanguinipes, to host plant odors and volatile components

AbstractThe attraction of the polyphagous grasshopper, Melanoplus sanguinipes (F.), to odors from plant foliage or to chemical components of these odors was tested in a glass Y‐tube olfactometer. Humidified air was passed at equal flow rates through a sample chamber containing plant material and an empty control chamber and then through the Y‐tube to the holding chamber containing the test insect. Solutions of volatile chemicals in water were metered at a constant rate into the sample air stream with a syringe pump. Insects moving upwind were recorded after entering either the sample or control arm of the Y‐tube. Both nymphs and adults were strongly attracted to the odor of chopped and intact seedling foliage of perennial ryegrass and wheat. Chopped leaves but not intact leaves of sorghum and alfalfa also were significantly attractive. The major components of ryegrass odor from both chopped and stem‐cut leaves were Z‐hex‐3‐en‐1‐yl acetate, Z‐hex‐3‐en‐1‐ol, and pent‐1‐en‐3‐ol, in that order, with lesser amounts of E‐hex‐2‐enal. Chopped leaves released many more minor components. The major components when tested individually or in binary and ternary mixtures were significantly attractive to grasshoppers compared to humidified air but not to the degree of whole plant odor. However, a quartenary mixture simulating the odor blend had levels of attractancy equal to that of chopped grass odor. Blends of these 5‐ and 6‐carbon unsaturated alcohols, esters, and aldehydes volatilizing from green plants probably play an important role as olfactory cues for orientation of grasshoppers to food plants.RésuméAttraction de Melanopus sanguinipes par des odeurs de feuillage de plantes et par leurs composés volatilesL'attraction de M. sanguinipes (F.) par l'odeur du feuillage et des composés chimiques de ces odeurs a été examinée dans un olfactomètrc en tube de verre en Y. Des flux identiques d'air humidifié étaient introduits dans une enceinte contenant le matériel végétal et dans une enceinte témoin, et, via le tube en Y, dans l'enceinte contenant l'insecte à étudier. Des solutions aqueuses de substances volatiles étaient introduites à un taux constant dans le courant d'air grâce à une seringue. Les insectes se déplaçant contre le vent étaient enregistrés après pénétration dans une branche déterminée du tube en Y. Larves et adultes étaient fortement attirés par l'odeur de feuillage intact ou coupé de semis de Lolium perenne et de blé (Triticum aestivum). Les feuilles coupées, mais non les fcuilles intactes de sorgho (Sorghum bicolor) et de luzerne (Medicago sativa) étaient, elles aussi, significativement attractives. Les principales substances constituant de l'odeur de feuilles de Lolium perenne, tant coupées qu'intactes, étaient dans l'ordre de Z‐hex‐3‐en‐1‐yl acétate, le Z‐hex‐3‐en‐1‐ol et le pent‐1‐en‐3‐ol, et dans une moindre mesure, E‐hex‐2‐enal. Les feuilles coupées libéraient beaucoup plus de composés secondaires. Les principaux constituants testés, seuls ou en mélanges binaires ou ternaires, étaient significativement attractifs, mais moins que l'odeur totale de la plante. Toutefois, un mélange quaternaire, simulant le mélange odorant, avait le même pouvoir attractif que l'odeur de la plante entière. L'union de ces alcools, esters et aldéhydes à 5‐ et 6‐carbones non saturês, volatilisés à partir des plantes vertes, jouent probablement un grand rôle comme signaux orientateurs lors de l'attraction des criquets par leur plantes alimentaires.

Sexual Role Reversal in Mate-Finding Strategies of the Cabbage Looper Moth

The mate-finding behavior of the cabbage looper moth Trichoplusia ni (Lepidoptera: Noctuidae) includes both female- and male-produced sex pheromones used in distinct mate-finding strategies. Both sexes release multicomponent pheromones attractive to the opposite sex. Male pheromone is comprised of d-linalool, m-cresol, and p-cresol released from abdominal hair pencils. Males exposed to host plant odor or to the female sex pheromone (Z)-7-dodecen-1-ol acetate are more attractive to females, suggesting stimulation of male pheromone release.

Control of olfactory-induced behavior in alfalfa seed chalcid (Hymenoptera: Eurytomidae) by celestial light

The behavioral response of female alfalfa seed chalcids is dependent on the polarization of sky light when exposed to olfactory stimuli between 1100 and 1500 hr. Females made no orientation flights to or landings on eight unbaited targets, but when half the targets were baited with the host-plant odor of hexyl acetate, they did make orientation flights to and landed on baited targets. Female preference for baited targets disappeared when natural sky light was plane polarized (at right angles to natural sky light polarization at 1200 hr). When natural sky light was passed through a diffuser filter to completely depolarize the light, females made numerous orientation flights but displayed no preference for baited targets. Any alteration of the natural wavelengths of sky light between 345 and 425 nm with various Kodak Wratten filters that excluded certain wavelengths produced similar results wherein females had no preference for baited or unbaited targets. The hypothesis that chalcid response was controlled by the polarization characteristics of sky light was confirmed when females again preferred baited targets in tests that were conducted 6 hr after sunrise, but they displayed no preference for baited targets when exposed to the mixture of polarized and nonpolarized light present in the sky 1-2 hr after sunrise or 1-2 hr before sunset. The possibility that chalcid response was due to a circadian rhythm was eliminated by exposure of insects to different sequences of light-dark regimes prior to the olfactory test.

Attraction of the cabbage looper to host plants and host plant odor in the laboratory

AbstractIn a laboratory flight tunnel, mated female, unmated female, and male adult cabbage loopers, Trichoplusia ni (Hübner), exhibited chemically mediated anemotaxis (attraction) in response to intact potted cabbage plants (Brassica oleracea L.), leading to contact with the plant. Similar attraction responses were also observed by mated females to potted soybean (Glycine max (L.)), tomato (Lycopersicon esculentum Miller), and celery (Apium graveolens L.) plants in noncompetitive comparisons. Mated females, unmated females, and males flew to cabbage plants throughout the scotophase. Response rates for mated females were higher than for unmated females and males. Mated female cabbage loopers were attracted by odors of cabbage, soybean, tomato, or celery piped into a flight tunnel from single plants held in glass jars and not to odors of the non‐host plant Setcreasea purpurea, or to humidified air. They were also attracted to water washings of cabbage at dosages of 0.4 to 2.0 gram equivalents, when presented on cotton dental wicks in the flight tunnel.RésuméAttraction au laboratoire de Trichoplusia ni par des plantes hôtes ou par l'odeur de plantes‐hôtesDans un tunnel de vol, des femelles vierges ou inséminées et des mâles de T. ni Hübner, réagissent par une anémotaxie chimique (attraction) à des plantes entières de Brassica oleracea L., ce qui a entraîné le contact avec le végétal. Avec Glycine max (L), Lycopersicon esculentum (Miller) et Apium graveolens (L), des attractions du même type ont été observées chez des femelles inséminées, mais en absence de compétition entre les plantes. Les femelles vierges et inséminées ainsi que les mâles volent vers le chou pendant la scotophase. Le taux de réactions des femelles inséminées a été le plus élevé. Dans un tunnel de vol, ces mêmes femelles étaient attirées par les odeurs de plantes isolées de chou, soja, tomate et céleri, mais non par celle de la plante non‐hôte, Setcreasea purpurea, ou par de l'air humide. Dans le tunnel de vol, elles ont été attirées aussi par des mèches de coton dentaire imprégnées d'eau de lavage de chou aux concentrations de 0,4 à 2,0 équivalents grammes.

Host-plant finding for oviposition by adult cabbage root fly, Delia radicum

Host-plant finding by female cabbage root fly, Delia radicum, begins once they have mated and become gravid. Host-plant odour detected downwind of plants induces an upwind anemotactic response, involving both mechano-orientation and take-off into the odour-laden wind from a fixed substrate and optomotor anemotaxis while in flight. The behavioural mechanisms involved in odour source location in D. radicum are broadly similar to other Diptera locating host-plant odours and to Lepidoptera locating pheromone sources. D. radicum integrates olfaction with other sensory modalities as a host-plant is approached, with vision becoming important within the vicinity of the plant. On arrival at the host-plant, chemo-reception and mechano-reception are used in host-plant acceptance, oviposition stimulation and the choice of an oviposition site. The host-plant finding behaviour culminating in oviposition could potentially be modified at any stage for pest control purposes.

Odour‐conditioned anemotaxis of apterous aphids (Cryptomyzus korschelti) in response to host plants

ABSTRACT. Orientation responses of adult apterous virginoparae of Cryptomyzus korschelti Börner were recorded using a locomotion‐compensator in front of a wind tunnel. Individual aphids were tested under four consecutive treatments: without wind; clean wind; and wind carrying odour of the host plant Stachys sylvatica or odour of a non‐host plant Solanum tuberosum. The walking tracks were tortuous in all treatments except when the odour of host plants was used. Host plant odour induced upwind orientation of aphids (odour‐conditioned positive anemotaxis). Track variables such as vector length, straightness, upwind time and upwind length, increased when the aphids moved upwind. Walking speeds were not affected. The simultaneous stimulation by wind and host plant odour caused aphids to walk upwind for more than 1 m in 10 min. These findings suggest that olfactory attraction of aphids is involved in host plant selection.

Misleading the Colorado potato beetle with an odor blend

Walking tracks of Colorado potato beetles,Leptinotarsa decemlineata Say, were recorded on a locomotion-compensator in response to wind, odors of host plantsSolanum tuberosum L. and nonhost plantsLycopersicon hirsutum f.glabratum C.H. Mull, and to mixtures of these plant species. Host-plant odor induced positive anemotactic responses in starved females, whereas odor of the nonhostL. hirsutum was neither repellent nor attractive. The attractiveness of host-plant odor, however, was neutralized in the odor blend of plant species. Masking the attractive host-plant odor will hinder the beetle's searching for host-plant patches, and this principle may be exploited in pest control by mixed cropping.

Effects of nonhost-plant odors on anemotactic response to host-plant odor in female cabbage root fly,Delia radicum, and carrot rust fly,Psila rosae

An inflatable polythene wind tunnel was used for behavioral assays of femaleD. radicum andP. rosae in diffuse host- and non-host-plant odor, alone and in combination. Host-plant odor caused an upwind anemotactic response in both species. Changes in fly distribution, relative to wind direction, occurred when onion odor was combined with host odor forD. radicum andP. rosae, and when sage odor was combined with carrot ordor forP. rosae. The assay has potential for screening volatiles for their behavior-modifying effects.

Masking of host plant odour in the olfactory orientation of the Colorado potato beetle

AbstractThe odour of potato plants Solanum tuberosum L., elicits a true odour‐conditioned positive anemotaxis in the Colorado potato beetle, Leptinotarsa decemlineata Say. Blending the odour of non‐host plant species, namely wild tomatoes Lycopersicon hirsutum f. glabratum C.H. Mull or cabbage Brassica oleracea L. var. gemmifera DC., with the attractive host plant odour blocks the release of upwind responses in non‐experienced as well as experienced females. The neutralization of the beetle's orientation responses is obtained without repellency. It is expected that masking of host plant odour occurs often in mixed cropping systems.RésuméMasquage de l'odeur de la plante hôte lors de l'orientation a longue distance du doryphoreUn certain nombre d'articles rapporte une diminution du nombre des insectes phytophages spécialistes comme une conséquence à la diversification des agroécosystèmes (Altieri & Letourneau, 1982; Cromartie, 1981; Kareiva, 1983; Risch et al., 1983). Ainsi, il a été supposé que la présence de plantes non‐hôtes pouvait interférer avec celle de plantes hôtes en modifiant la nature des informations chimiques parvenant aux insectes. Les modifications comportementales qui peuvent en résulter lors de l'attraction à distance sont toutefois encore peu claires. Les expérimentations présentées ici analysent les réponses individuelles du doryphore à diverses stimulations olfactives issues de plantes entières. Des femalles ont été ainsi étudiées un jour après l'émergeance en présence d'air vierge et d'air chargé d'odeurs de Solanum tuberosum, Lycopersicon hirsutum f. glabratum, Brassica oleracea var. gemmifera, ainsi que des mélanges S. tuberosum avec L. hirsutum et S. tuberosum avec B. oleracea. A partir de l'enregistrement continu de l'activité locomotrice dans chaque condition (à l'aide du compensateur de locomotion), nous avons déterminé que L. hirsutum et B. oleracea masquaient l'odeur de la plante hôte S. tuberosum en supprimant la réponse anémotactique positive conditionnée par l'odeur de cette dernière. Les mélanges d'odeurs ainsi obtenus sont considérés comme neutres pour l'orientation à longue distance du doryphore. L'expérience préalable par le doryphore de l'ingestion de feuillage de pomme de terre ne modifie pas l'effet du camouflage obtenu. Ces résultats laissent penser qu'il est possible de limiter la découverte de la plante hôte chez les insectes, et que les méthodes de camouflages olfactives pourraient prévenir les attaques de certains ravageurs.

Host Odor Perception in Phytophagous Insects

Phytophagous insects show specialized feeding habits. In general, each species feeds on a restricted range of taxonomically related plant species and in addition limits its feeding to particular plant parts. Most studies on insect-plant rela­ tionships concern pest species in agricultural systems, which do not show the stability of the insect's original ecosystem. In monocultures host plants of high quality are present over large areas. Despite the biased nature of these in­ teractions, some generations of insects are forced to disperse and must find new host plants on which feeding results in growth and reproduction. (182). Host selection in phytophagous insects consists of a sequence of behavioral re­ sponses to an array of stimuli associated with host and nonhost plants. The insects are equipped with sensory receptors enabling them to perceive these stimuli. Plant stimuli involved include in varying proportions visual, mechani­ cal, gustatory, and olfactory characteristics (158). Plant odors have been considered of minor importance in host selection for many insect species, especially those that perform as r-strategists (93). This view needs to be reconsidered because such insects as aphids (21, 121, 122), whiteflies (173), and rice brown planthoppers (117), possess the full equipment of olfactory receptors and are attracted by host plant odors. In the present review selection was made mainly from the literature of the last 20 years. Floral relationships and social insects were excluded. Readers are invited to consult related reviews (49, 145, 158) as well as Dethier (27) for older Iiterature .