Using Chemical Ecology to Enhance Weed Biological Control

In agricultural systems, chemical ecology and the use of semiochemicals have become critical components of integrated pest management. The categories of semiochemicals that have been used include sex pheromones, aggregation pheromones, and plant volatile compounds used as attractants as well as repellents. In contrast, semiochemicals are rarely utilized for management of insects used in weed biological control. Here, we advocate for the benefit of chemical ecology principles in the implementation of weed biocontrol by describing successful utilization of semiochemicals for release, monitoring and manipulation of weed biocontrol agent populations. The potential for more widespread adoption and successful implementation of semiochemicals justifies multidisciplinary collaborations and increased research on how semiochemicals and chemical ecology can enhance weed biocontrol programs.

Agasicles hygrophila attack increases nerolidol synthase gene expression in Alternanthera philoxeroides, facilitating host finding

Herbivorous insects use plant volatile compounds to find their host plants for feeding and egg deposition. The monophagous beetle Agasicles hygrophila uses a volatile (E)-4,8-dimethyl-1,3,7-nonanetriene (DMNT) to recognize its host plant Alternanthera philoxeroides. Alternanthera philoxeroides releases DMNT in response to A. hygrophila attack and nerolidol synthase (NES) is a key enzyme in DMNT biosynthesis; however, the effect of A. hygrophila on NES expression remains unclear. In this study, the A. philoxeroides transcriptome was sequenced and six putative NES genes belonging to the terpene synthase-g family were characterized. The expression of these NES genes was assayed at different times following A. hygrophila contact, feeding or mechanical wounding. Results showed that A. hygrophila contact and feeding induced NES expression more rapidly and more intensely than mechanical wounding alone. This may account for a large release of DMNT following A. hygrophila feeding in a previous study and subsequently facilitate A. hygrophila to find host plants. Our research provides a powerful genetic platform for studying invasive plants and lays the foundation for further elucidating the molecular mechanisms of the interaction between A. philoxeroides and its specialist A. hygrophila.

Leafroller-induced phenylacetonitrile and acetic acid attract adult Lobesia botrana in European vineyards

We recently identified unique caterpillar-induced plant volatile compounds emitted from apple leaves infested with the larvae of various leafroller species. In subsequent field tests, binary blends of phenylacetonitrile+acetic acid and 2-phenylethanol+acetic acid were found to be attractive to a range of tortricid leafroller species (Tortricidae: Tortricinae) in both the Southern and Northern Hemispheres. In this work, the caterpillar-induced plant volatiles from the apple-leafroller system were tested in two vineyards in Spain and Hungary for their attractiveness to the grape frugivore Lobesia botrana (Tortricidae: Olethreutinae). As seen for Tortricinae species, a binary blend of phenylacetonitrile+acetic acid attracted significantly more male and female L. botrana to traps than acetic acid or blank lures. Traps baited with other caterpillar-induced plant volatile compounds (benzyl alcohol, 2-phenylethanol, indole, and (E)-nerolidol, each as a binary blend with acetic acid) did not catch significantly more moths than traps containing acetic acid alone. The catches of male and female moths support an optimistic future for new products in female tortricid surveillance and control that are based on combinations of kairomone compounds released from larval-damaged foliage.

Electroantennogram, behavioural responses, and field trapping of Trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae) to eight host volatiles

Trypophloeus klimeschiEggers (Coleoptera: Curculionidae: Scolytinae) was first discovered in China in 2003, and it exhibits strong species specificity toPopulus albavar.pyramidalisBunge (Salicaceae). To screen plant volatile compounds for monitoring and trappingT. klimeschi, the electroantennogram responses of adultT. klimeschito eight plant volatiles, including nonanal, 2-methylbutanal, decanal, 2-hydroxybenzaldehyde, (Z)-3-hexen-1-ol benzoate, methyl benzoate, methyl salicylate, and geraniol were tested at various concentrations. Behavioural responses of female and male adults to various concentrations of these eight plant volatiles were also determined using a Y-tube olfactometer. We then tested the effectiveness of these compounds as lures for trappingT. klimeschiin the field. Electroantennogram tests showed thatT. klimeschipossesses olfactory sensitivity for eight compounds. Additionally, walkingT. klimeschiexhibited attraction to low concentrations (≤ 1 μg/μL) of all eight compounds in Y-tube olfactometer. Field experiment results indicated that baits composed of each volatile compound alone were more attractive to greater numbers ofT.klimeschithan the control. The methyl benzoate bait was better attracted byT.klimeschithan other tested volatiles. These results suggest that these compounds could be used in attraction of this stem-boring pest. This study could have important implications for the development of an effective semiochemical-based management tool forT. klimeschiin the field.

Analytical method for metabolites involved in biosynthesis of plant volatile compounds

The progress in the successful techniques used for studying metabolites involved in the metabolic routes of plant volatiles is summarized.