Species-Specific Induction of Plant Volatiles by Two Aphid Species in Apple: Real Time Measurement of Plant Emission and Attraction of Lacewings in the Wind Tunnel.

Upon damage by herbivores, plants release herbivory-induced plant volatiles (HIPVs). To find their prey, the pest's natural enemies need to be fine-tuned to the composition of these volatiles. Whereas standard methods can be used in the identification and quantitation of HIPVs, more recently introduced techniques such as PTR-ToF-MS provide temporal patterns of the volatile release and detect additional compounds. In this study, we compared the volatile profile of apple trees infested with two aphid species, the green apple aphid Aphis pomi, and the rosy apple aphid Dysaphis plantaginea, by CLSA-GC-MS complemented by PTR-ToF-MS. Compounds commonly released in conjunction with both species include nonanal, decanal, methyl salicylate, geranyl acetone, (Z)-3-hexenyl acetate, (Z)-3-hexenyl butanoate, (Z)-3-hexenyl 2-methyl-butanoate, (E)-ß-caryophyllene, ß-bourbonene and (Z)-3-hexenyl benzoate. In addition, benzaldehyde and (E)-ß-farnesene were exclusively associated with A. pomi, whereas linalool, (E)-4,8-dimethyl-1,3,7-nonatriene were exclusively associated with D. plantaginea. PTR-ToF-MS additionally detected acetic acid (AA) and 2-phenylethanol (PET) in the blends of both trees attacked by aphid species. In the wind tunnel, the aphid predator, Chrysoperla carnea (Stephens), responded strongly to a blend of AA and PET, much stronger than to AA or PET alone. The addition of common and species-specific HIPVs did not increase the response to the binary blend of AA and PET. In our setup, two host-associated volatiles AA + PET appeared sufficient in the attraction of C. carnea. Our results also show the importance of combining complementary methods to decipher the odor profile associated with plants under pest attack and identify behaviourally active components for predators.

Designing a species-selective lure based on microbial volatiles to target Lobesia botrana.

Sustainable, low impact control methods, including mating disruption and microbial insecticides against L. botrana have been available for decades. Yet, successful implementation has been restricted to only a few grapevine districts in the world. A limiting factor is the lack of a female attractant to either monitor or control the damaging sex. Volatile attractants for both female and male insects can be used to assess when L. botrana populations exceed economic thresholds, and to decrease the use of synthetic pesticides within both conventional and pheromone programs. Rather than using host-plant volatiles, which are readily masked by background volatiles released by the main crop, we tested the attractiveness of volatiles that signify microbial breakdown and more likely stand out against the background odour. A two-component blend of 2-phenylethanol (2-PET) and acetic acid (AA) caught significant numbers of both sexes. Catches increased with AA and, to a minimal extent, 2-PET loads. However, a higher load of 2-PET also increased bycatches, especially of Lepidoptera and Neuroptera. Major (ethanol, ethyl acetate, 3-methyl-1-butanol) or minor (esters, aldehydes, alcohols and a ketone) fermentation volatiles, did surprisingly not improve the attraction of L. botrana compared to the binary blend of 2-PET and AA alone, but strongly increased bycatches. The most attractive lure may thus not be the best choice in terms of specificity. We suggest that future research papers always disclose all bycatches to permit evaluation of lures in terms of sustainability.

Translating olfactomes into attractants: shared volatiles provide attractive bridges for polyphagy in fruit flies.

Tephritid flies are serious fruit pests. Despite clear niche differences, many species show considerable overlap in fruit preferences, of which we here analysed the olfactory correlate. Using the volatiles of four unrelated fruit species, antennal responses were quantified to construct a fruit-odour response database for four tephritid species. Although responses were distinct with a significant niche-correlated bias, the analyses show that the probability of detection of a volatile strongly increased with its sharedness across fruits. This also held for the unrelated fruit fly Drosophila melanogaster (DoOR repository-based analyses). We conjectured that shared volatiles signify 'host' to the fly 'nose' and induce attraction. Indeed, blends of volatiles shared by fruit and detected by all four species were very attractive for tephritid species, more than fruits. Quantitative whole antennal recordings en lieu of, or complementing bottom-up molecular neurogenetic approaches, enables comparative olfactomics in non-model species, and facilitate interpretation of olfaction in evolutionary, ecological, and applied contexts.

Potential of locally sustainable food baits and traps against the Mediterranean fruit fly Ceratitis capitata in Bolivia.

BACKGROUND: Small-scale farmers often take a double hit from pests such as tephritid fruit-flies. The high price of products against fruit-flies, together with the higher risk of reinfestation from neighboring orchards, limits options for control. Therefore, management requires low-cost local products and concerted action. Peach production in central Bolivia is increasingly affected by invasive Ceratitis capitata. To provide locally sustainable techniques that could incentivize area-wide cooperation of growers, we tested efficiency and specificity of low-cost lures and traps compared with commercial lures and traps (Tephritrap). RESULTS: In the laboratory, the local fermented beverage 'chicha' and baker's yeast were equally or more attractive than commercial lures. Both chicha and baker's yeast trapped more flies in field (average FTD 10.31 and 9.49), whereas commercially hydrolyzed protein lure (4.71) or Torula yeast (6.82). However, many non-target species were caught (57.3% and 53.4%). Of the six PET bottles-based traps used, the T-trap caught a similar number of flies (average FTD 5.55), but fewer beneficial insects (0.16) compared to the Tephritrap (0.92). CONCLUSIONS: This study provides fruit growers with an economical and effective method to capture large numbers of C. capitata, suitable to be part of integrated pest management programs for fruit fly control. © 2018 Society of Chemical Industry.

Volatiles of Grape Inoculated with Microorganisms: Modulation of Grapevine Moth Oviposition and Field Attraction.

Semiochemicals released by plant-microbe associations are used by herbivorous insects to access and evaluate food resources and oviposition sites. Adult insects may utilize microbial-derived nutrients to prolong their lifespan, promote egg development, and offer a high nutritional substrate to their offspring. Here, we examined the behavioral role of semiochemicals from grape-microbe interactions on oviposition and field attraction of the grapevine moth Lobesia botrana (Denis & Schiffermüller). The volatile constituents released by grape inoculated with yeasts (Hanseniaspora uvarum (Niehaus), Metschnikowia pulcherrima (Pitt.) M.W. Miller, Pichia anomala, Saccharomyces cerevisiae Meyen ex E.C. Hansen, and Zygosaccharomyces rouxii (Boutroux) Yarrow), sour rot bacteria (Acetobacter aceti (Pasteur) Beijerinck and Gluconobacter oxydans (Henneberg) De Ley), and a fungal pathogen (Botrytis cinerea Pers.) all endemic of the vineyard were sampled by solid-phase microextraction and analyzed by gas-chromatography coupled with mass spectrometry. Ethanol, 3-methyl-1-butanol, and ethyl acetate were the most common volatiles released from all microbe-inoculated grapes. In addition, acetic acid was released at a substantial amount following bacteria inoculation and in a three-way inoculation with yeasts and the fungus. 2-phenylethanol, a compound reported to attract tortricid moths when used in combination with acetic acid, was found at a relatively low level in all microbial combinations as well as in the control grape. While grapes inoculated with a consortium of yeasts stimulated oviposition in comparison with uninoculated berries, the phytopathogenic fungus deterred egg-laying. Nonetheless, the highest preference to lay eggs was measured when the yeasts were co-inoculated with the fungus. The lowest preference was obtained when grapes were inoculated with sour rot bacteria and their binary co-inoculation with yeasts and the fungus. Interestingly, oviposition on berries simultaneously inoculated with all the three microbial groups was unaffected. Lures loaded with either acetic acid or 2-phenylethanol were not attractive when placed in traps as single component in vineyards, but a binary blend attracted both sexes of grapevine moth in significant numbers. Further addition of the three most common volatiles released by infected berries (ethanol, 3-methyl-1-butanol, and ethyl acetate) did not significantly increase moth catch with this binary blend. The ecological implications of the grape-microorganism and grapevine moth interaction as well as the possibility to develop a pest monitoring system based on microbial volatiles are discussed.