The role of volatiles in aggregation and host-seeking of the haematophagous poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae)

Infestations with ectoparasitic poultry red mites (Dermanyssus gallinae) pose an increasing threat to poultry health and welfare. Because of resistance to acaricides and higher scrutiny of poultry products, alternative and environmentally safe management strategies are warranted. Therefore, we investigated how volatile cues shape the behavior of D. gallinae and how this knowledge may be exploited in the development of an attractand- kill method to control mite populations. A Y-tube olfactometer bio-assay was used to evaluate choices of mites in response to cues related to conspecific mites as well as related to their chicken host. Both recently fed and starved mites showed a strong preference (84 and 85%, respectively) for volatiles from conspecific, fed mites as compared to a control stream of clean air. Mites were also significantly attracted to ‘aged feathers’ (that had remained in the litter for 3–4 days), but not to ‘fresh feathers’. Interestingly, an air stream containing 2.5% CO2, which mimics the natural concentration in air exhaled by chickens, did attract fed mites, but inhibited the attraction of unfed mites towards volatiles from aged feathers. We conclude that both mite-related cues (aggregation pheromones) and host-related cues (kairomones) mediate the behavior of the poultry mite. We discuss the options to exploit this knowledge as the ‘attract’ component of attract-and-kill strategies for the control of D. gallina

Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest

Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects

Thrips responses to plant odours

Thrips responses to plant odour compounds were assessed using a Y-tube olfactometer. Several compounds were attractive to adult Frankliniella occidentalis females, since the majority walked towards the odour source. Some odours that were attractive for western flower thrips appeared to be non-attractive for Thrips tabaci and visa versa. Chrysanthemum buds or flowers that were used as an odour source in the olfactometer elicited no positive response from western flower thrips. In wind tunnel experiments, where thrips could use both olfaction and vision, thrips preferred to settle on open chrysanthemum flowers when buds were the alternative. When flowers and buds were covered with a perforated hood, preventing visual orientation, there was no difference in numbers of thrips settling on buds and open flowers. This indicates that colour is a dominant factor for thrips orientation towards flower

Potential application of a Gulf Coast Tick, Amblyomma maculatum Koch, Aggregation-Attachment-Pheromone for surveillance of free-living adults

The aggregation-attachment-pheromone (AAP) of two geographic strains of the Gulf Coast tick, Amblyomma maculatum Koch, was investigated to evaluate practicality of using solid-phase-microextraction (SPME) in an AAP study of Gulf Coast tick. Solid-phase microextraction was used to compare the AAP production in two strains of fed male Gulf Coast tick and demonstrate and confirm the presence of AAP in bioassays. A solid-phase-microextraction (SPME) headspace collection technique was sufficient to capture volatile organic compounds produced by fed and unfed male Gulf Coast ticks. Gas chromatography analysis revealed three major volatile organic compounds were produced in significantly greater amounts (p < 0.05) by fed males than those produced by unfed males. These volatile compounds were produced in significantly higher amount by the third day of feeding by male ticks. However, two of these volatiles remained relatively constant in their production while the primary volatile compound increased in its production until the eighth day of feeding by male Gulf Coast ticks. Also, the relative abundances of these three volatile organic compounds were different between Oklahoma and Texas strains of Gulf Coast ticks. The activity of AAP from fed male Gulf Coast ticks was confirmed using two bioassay techniques. A petri dish bioassay revealed significantly higher numbers of female Gulf Coast ticks attracted to fed-males which also produced significantly greater amounts (p < 0.001) of volatile organic compounds detected by GC analysis. The Ytube olfactometer bioassay revealed that significantly higher numbers of females responded to fed-males or to CO2 when compared to purified air (p < 0.001), but the differences in female response to fed-males and CO2 were not significant (p < 0.391 in Oklahoma strain and p < 0.458 in Texas strain). However, female responses to stimuli containing both fed-males and CO2 were significantly higher when compared to either stimulus alone (p < 0.001)

Electrophysiological and Behavioral Responses of Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae) to Cereal Grain Volatiles

Volatiles emitted by the host's food would be the first signals used by parasitoids in the host location process and are thought to play an important role in host habitat location. In this study, the olfactory responses of Theocolax elegans (Westwood), a Pteromalid wasp that parasitizes immature stages of stored-product insect pests developing inside cereal or leguminous grains, to volatiles emitted by healthy wheat grains, their hexane extracts, and different doses of three individual compounds previously identified in cereal grain odors were investigated in Y-tube olfactometer and Petri dish arena behavioral bioassays and electroantennogram recordings. In Y-tube olfactometer bioassays, odors from healthy wheat grains and their hexane extracts were attractive to both sexes of T. elegans. Moreover, hexane extracts elicited arresting effects in Petri dish arena. The three synthetic compounds valeraldehyde, maltol, and vanillin elicited dose-dependent responses in both male and female adult wasps confirming the capability of the peripheral olfactory systems to perceive cereal volatiles. In behavioral bioassays, different doses of vanillin were significantly attractive to both sexes

The predatory mite Typhlodromalus aripo prefers greenmite induced plant odours from pubescent cassava varieties

Article PurchasedIt is well known that plant-inhabiting predators use herbivore-induced plant volatiles to locate herbivores being their prey. Much less known, however, is the phenomenon that genotypes of the same host plant species vary in the attractiveness of these induced chemical signals, whereas they also differ in characteristics that affect the predator’s foraging success, such as leaf pubescence. In a series of two-choice experiments (using a Y-tube olfactometer) we determined the preference of Typhlodromalus aripo for pubescent versus glabrous cassava cultivars infested with the cassava green mite Mononychellus tanajoa and also the preference for cultivars within each of the two groups. We found that when offered a choice between pubescent and glabrous cassava cultivars (either apex or leaves), T. aripo was significantly more attracted to pubescent cultivars. For each cultivar, M. tanajoa infested leaves and apices were equally attractive to T. aripo. There was however some variation in the response of T. aripo to M. tanajoa-infested plant parts within the group of pubescent cultivars, as well as within the group of glabrous cultivars. Our study confirms not only that T. aripo uses herbivore-induced plant volatiles to search for prey in cassava fields, but it also shows that it can discriminate between glabrous and pubescent cultivars and prefers the latter. This knowledge can be useful in selecting cultivars that are attractive and suitable to T. aripo, which, in turn, may promote biological control of the cassava green mite

Behavioral Responses of Apis mellifera Adult Workers to Odors from Healthy Brood and Diseased Brood

Studies of adult workers’ responses to infected brood were undertaken to isolate discrete volatile compounds that elicited honeybee hygienic behavior. Using a freeze-killed brood assay, we determined that in healthy colonies adult workers recognized and emptied infected cells with a 95% clearance rate. SPME-GC-MS results emptied &gt;95% infected cells indicated differences in the composition and relative content of volatile compounds released by healthy and diseased brood. Additionally, we determined that the main volatile compound released from the pathogen Ascosphaera apis was phenethyl alcohol. The Y-tube olfactometer indicated that 10- to 20-day-old workers of healthy colonies, but only 15-day-old workers of diseased colonies, were significantly sensitive to differences in characteristic volatile compounds. This information could facilitate honey bee selection based on mechanisms that contribute to chalkbrood disease tolerance

Beauveria bassiana (Hypocreales: Clavicipitaceae) Volatile Organic Compounds (VOCs) Repel Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae)

The entomopathogenic fungus Beauveria bassiana (Bb) is used to control the red palm weevil (RPW) Rhyncophorus ferrugineus (Oliver). Beuveria bassiana can infect and kill all developmental stages of RPW. We found that a solid formulate of B. bassiana isolate 203 (Bb203; CBS 121097), obtained from naturally infected RPW adults, repels RPW females. Fungi, and entomopathogens in particular, can produce volatile organic compounds (VOCs). VOCs from Bb203 were analyzed using gas chromatography-mass spectrometry (GC-MS). GC-MS identified more than 15 VOCs in B. bassiana not present in uninoculated (control) formulate. Both ethenyl benzene and benzothiazole B. bassiana VOCs can repel RPW females. Our findings suggest that B. bassiana and its VOCs can be used for sustainable management of RPW. They could act complementarily to avoid RPW infestation in palms.This work was supported by the Spanish Ministry of Science and Innovation AGL2015-66833-R project, the Universiti Kebangsaan Malaysia, and the Malaysia Ministry of Higher Education. Project was also partially supported by MUSA project (727624). The results of this paper have been filed for a Spanish Patent (P201631534)

Evaluation of volatile organic compounds from broccoli plants infested with Myzus persicae and parasitoids Aphidius colemani attraction

Volatile organic compounds (VOCs) from uninfested and infested broccoli plant samples with green peach aphid Myzus persicae were investigated by headspace solid microextraction (HS-SPME) combined with gas chromatography mass spectrometry (GC-MS). Overall, 25 compounds were identified in uninfested and infested broccoli plants. The HS-SPME combined with GC-MS analysis of the volatiles described the differences between the infested and uninfested broccoli plant samples. Based on peak area from the GC-MS analysis, the VOCs from infested broccoli were significantly greater than that from uninfested broccoli, such as D-limonene, Undecane, 3,4-dimethyl-, Heptane, alpha-Pinene, Oxalic acid, Citronellol, Tridecane, n-Decanoic acid, Cyclopentane, pentyl- and n-Hexadecanoic acid compared with volatiles released from uninfested broccoli. The results of Y-tube olfactometer showed that Myzus persicae were significantly attracted by the VOCs released from infested broccoli plants, more than uninfested plants or clean air. The percentage of aphid choice was 70% towards infested broccoli, and 10% were attracted to the clean air choice and uninfested plants. With the comparison between clean air and uninfested plants, the aphids were attracted by 84% for broccoli, while 7% were attracted towards clean air. Comparing between infested and uninfested, the aphid attracted by 26.6% for infested broccoli, versus 30% for uninfested broccoli. The preferences of Aphidus colemani to the infested, uninfested plants with M. persicae and compared with clean air were measured. The results indicated that parasitoids could discriminate the infested broccoli and significantly respond to the plant odour and attractive by 100% for the parasitoid towards infested broccoli plants