Identification and application of bacterial volatiles to attract a generalist aphid parasitoid: from laboratory to greenhouse assays

Abstract

BACKGROUND Recent studies have shown that microorganisms emit volatile compounds that affect insect behaviour. However, it remains largely unclear whether microbes can be exploited as a source of attractants to improve biological control of insect pests. In this study, we used a combination of coupled gas chromatography‐electroantennography (GC–EAG) and Y‐tube olfactometer bioassays to identify attractive compounds in the volatile extracts of three bacterial strains that are associated with the habitat of the generalist aphid parasitoid Aphidius colemani, and to create mixtures of synthetic compounds to find attractive blends for A. colemani. Subsequently, the most attractive blend was evaluated in two‐choice cage experiments under greenhouse conditions. RESULTS GC–EAG analysis revealed 20 compounds that were linked to behaviourally attractive bacterial strains. A mixture of two EAG‐active compounds, styrene and benzaldehyde applied at a respective dose of 1 μg and 10 ng, was more attractive than the single compounds or the culture medium of the bacteria in Y‐tube olfactometer bioassays. Application of this synthetic mixture under greenhouse conditions resulted in significant attraction of the parasitoids, and outperformed application of the bacterial culture medium. CONCLUSION Compounds isolated from bacterial blends were capable of attracting parasitoids both in laboratory and greenhouse assays, indicating that microbial cultures are an effective source of insect attractants. This opens new opportunities to attract and retain natural enemies of pest species and to enhance biological pest control.

Impact of endophytic colonization by entomopathogenic fungi on the behavior and life history of the tobacco peach aphid Myzus persicae var. nicotianae

“…Aphid olfactory response in the Y-tube assays was analyzed using a Generalized Linear Mixed Model (GLMM) based on a binomial distribution with a logit link function (logistic regression) using inoculation treatment as a fixed factor (performed with the ‘glmer’ function from the lme4 package) [ 43 ]. Each release of one cohort of five individuals served as a replicate, giving a total of 24 replicates.…”

Aphid‐repellent, ladybug‐attraction activities, and binding mechanism of methyl salicylate derivatives containing geraniol moiety

“…Under the same conditions and procedures, the behavioral bioassay of male ladybugs was performed. The attractive activity was calculated by the preference index (PI), 43 PI = ( T − C )/( T + C ) × 100%, where T and C indicate the number of ladybugs in the treatment and control bottles, respectively. The choice values in the treatment and control bottles were compared using the x 2 goodness‐of‐fit test.…”

Bacterial Isolates Derived from Nest Soil Affect the Attraction and Digging Behavior of Workers of the Red Imported Fire Ant, Solenopsis invicta Buren

“…The dose-dependent results were similar to what has been described in other insect–bacteria interactions [ 56 ]. Identification of the specific bacterial metabolites that elicit RIFA repellency and attraction would allow dose-response experiments to be carried out [ 57 , 58 ]. Chemical identification of repellent metabolites might lead to the development of repellent compounds to protect electrical and other equipment from damage by RIFA.…”