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Chemical Interaction Between the Sugarcane Stem Borer, Chilo sacchariphagus, and the Trap Crop Erianthus arundinaceus

Jacob V., Tibere R., Nibouche S.. 2018. In : Abstracts of the ISSCT X Entomology Workshop - Solving Regional Arthropod Management Challenges in a Global World. Belle Glade : ISSCT, p. 9-9. ISSCT Entomology workshop ¿Solving Regional Arthropod Management Challenges in a Global World¿. 10, 2018-12-02/2018-12-07, Belle Glade (Etats-Unis).

Sugarcane yield losses due to the sugarcane stem borer, Chilo sacchariphagus, are reduced when plants of Erianthus arundinaceus, a close relative to sugarcane, are dispatched at the border of sugarcane fields. Previous studies showed that C. sacchariphagus females lay preferentially their eggs on E. arundinaceus and that newly emerged larvae are unable to reach adulthood. E. arundinaceus is used currently in Reunion Island as a trap crop in an integrated agricultural system reminiscent of the push-pull system introduced in Kenya to control maize stem borers. We explored the chemical mechanisms underlying this insect-plant interaction. The volatile compounds released by intact plants were collected at dusk and analyzed with a thermodesorber, a gas chromatograph, and a mass spectrometer. This protocol was repeated on seven accessions of Erianthus and one sugarcane cultivar susceptible to C. sacchariphagus. We identified 80 compounds, 10 that were sugarcane specific and two (noted compounds A and B) that were Erianthus specific (ANOVA, p<0.05, n=10 per accession and species). We then tested the electroantennographic response of C. sacchariphagus to compounds A and B and found that both sexes are sensitive to compound A only (response threshold: 10-2 dilution, p<0.01 sign rank test, n=10), but with an olfactory sensitivity smaller than for the sugarcane compound linalool (response threshold: 10-3 dilution, p<0.01 sign rank test, n=8). Finally, we tested the olfactory orientation behavior of gravid C. sacchariphagus females in a Y-olfactometer at dusk. These insects spend significantly more time in the branch of the olfactometer with compound A than in the branch with clean air (bootstrap test, p<0.01, n=14). Our study suggests that compound A might be a key compound in the attraction of C. sacchariphagus by E. arundinaceus. This mechanism might be targeted to improve the strategies of management of C. sacchariphagus in infested areas.

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