Volatiles of grape inoculated with microorganisms: Modulation of grapevine moth oviposition and field attraction

Authors: TASSIN, MARCO - Swedish University Of Agricultural Sciences; HERRERA, SEBASTIAN - Swedish University Of Agricultural Sciences; Knight, Alan; BARROS-PRADA, WILSON - University Of Talca; CONTRERAS, EDUARDO - University Of Talca; PERTOT, ILARIA - University Of Trento, Italy

Submitted to: Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2018
Publication Date: 3/10/2018
Citation: Tassin, M., Herrera, S., Knight, A.L., Barros-Prada, W., Contreras, E., Pertot, I. 2018. Volatiles of grape inoculated with microorganisms: Modulation of grapevine moth oviposition and field attraction. Microbial Ecology. https://doi.org/10.1007/s00248-018-1164-6.
DOI: https://doi.org/10.1007/s00248-018-1164-6

Interpretive Summary: Effective, low-cost monitoring of tree fruit pests is an important component of developing integrated programs which can minimize the use of insecticides. Researchers at the USDA, ARS, Temperate Tree Fruit and Vegetable Research Unit, Wapato, WA in collaboration with researchers in Sweden and Chile evaluated whether a new lure developed with volatiles released by yeasts in previous studies with moth pests of tree fruits could also be effective for the key moth pest of grape. It was determined that the new lure was effective and caught both sexes. Information from this research supports the continued effort to develop even more effective lures that can be used in trap-based monitoring program for important moth pests in fruit crops.

Technical Abstract: 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 behavioural 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, sour rot bacteria, and a fungal pathogen all endemic of the vineyard were sampled by solid-phase microextraction and analyzed by gas-chromatography coupled to 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.