Cultivar-dependent facilitation of other aphids by M. sacchari J.P. Michaud Kansas State University Sorghum – Sugarcane Aphid Research Exchange Meeting Dallas, TX January 3 – 4, 2017

Introduction Hysteroneura setaria Schizaphis graminum Sipha flava Aphid species recorded co-infesting with M. sacchari on either sorghum or johnsongrass: H. setaria S. maydis Hysteroneura setaria Schizaphis graminum Sipha flava Sipha maydis Rhopalosiphum maidis Rhopalosiphum padi

Materials & Methods We reared SCA + GB (+ BCOA), alone and together, on pairs of sorghum cultivars Either: 10 GB, 10 SCA, or 5 GB + 5 SCA - all 1st instars (< 12 h old) P8500 vs KS116B (SCA + GB) P8500 vs PI 550610 (SCA + BCOA) Last aphid to molt to adult left to reproduce on the same plant All life history data recorded daily - survival, developmental time, reproduction

Aphid treatment Developmental time (days) Developmental times for SCA and GB on P8500, both alone and together (GB+ and SCA+) a b c Developmental time (days) c Aphid treatment

Aphid treatment Developmental time (days) Developmental times for SCA and GB on KS116B, both alone and together (GB+ and SCA+) a ab b ab Developmental time (days) Aphid treatment

Nymphal survival (%) Aphid treatment Nymphal survival for SCA and GB on P8500, both alone and together (GB+ and SCA+) a a ab b Nymphal survival (%) Aphid treatment

Nymphal survival (%) Aphid treatment Nymphal survival for SCA and GB on KS 116B, both alone and together (GB+ and SCA+) Nymphal survival (%) a b ab b Aphid treatment

Relative reproductive rates of SCA & GB at (23 °C) infesting P8500 either alone or together (GB+ and SCA+) Time (days) GB benefits from SCA, SCA unaffected

Relative reproductive rates of SCA vs GB at (23 °C) infesting KS 116B either alone or together (GB+ and SCA+) Time (days) GB disadvantaged by SCA, SCA unaffected

Life tables for SCA and GB infesting plants either alone or together (GB+ and SCA+) Cultivar determines commensalism or amensalism (facilitation or interference)

Nymphal survival (%) Aphid treatment Nymphal survival for SCA and BCOA on P8500 and PI 550610, both alone and together (GB+ and SCA+) ab Nymphal survival (%) Aphid treatment

Aphid treatment Developmentlal time (days) Developmental time for SCA and GB on P8500 and PI 550610, both alone and together (BCOA+ and SCA+) a a ab b a a a b Developmentlal time (days) Aphid treatment

12-day fecundity (no. nymphs) Reproductive performance of SCA and GB on P8500 and PI 550610, both alone and together (BCOA+ and SCA+) a b a 12-day fecundity (no. nymphs) b c d c d Aphid treatment

Key Learnings Greenbug: SCA improved performance of GB on one variety and diminished it on another, while SCA was unaffected Bird-cherry oat aphid: SCA improved performance of BCOA on both varieties, with SCA performance diminished by BCOA on both, but more so on the less suitable one SCA has the ability to improve the suitability of susceptible sorghums for other aphids, but effects vary with the identity of the co-infesting aphid and the cultivar of the host plant Effective resistance to SCA should counter or eliminate this facilitation of other aphid species