Cultivardependent facilitation of other aphids by M sacchari

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 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 1 st instars (< 12 h old) • P 8500 vs KS 116 B (SCA + GB) • P 8500 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

Developmental times for SCA and GB on P 8500, both alone and together (GB+ and SCA+) Developmental time (days) 10 8 6 a b c c SCA+ 4 2 0 GB GB+ Aphid treatment

Developmental time (days) Developmental times for SCA and GB on KS 116 B, both alone and together (GB+ and SCA+) 10 8 a b ab GB+ SCA ab 6 4 2 0 GB Aphid treatment SCA+

Nymphal survival for SCA and GB on P 8500, both alone and together (GB+ and SCA+) Nymphal survival (%) 100 80 a a b 60 ab 40 20 0 GB GB+ SCA Aphid treatment SCA+

Nymphal survival for SCA and GB on KS 116 B, both alone and together (GB+ and SCA+) Nymphal survival (%) 100 80 60 40 a 20 0 GB b b ab GB+ SCA+ Aphid treatment

Relative reproductive rates of SCA & GB at (23 °C) infesting P 8500 either alone or together (GB+ and SCA+) 8 GB GB+ 6 SCA+ 4 2 0 1 3 5 7 9 11 13 15 17 19 21 23 Time (days) GB benefits from SCA, SCA unaffected 25 27

Relative reproductive rates of SCA vs GB at (23 °C) infesting KS 116 B either alone or together (GB+ and SCA+) 8 GB GB+ 6 SCA+ 4 2 0 1 3 5 7 9 11 13 15 17 19 21 23 Time (days) GB disadvantaged by SCA, SCA unaffected 25 27

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 for SCA and BCOA on P 8500 and PI 550610, both alone and together (GB+ and SCA+) Nymphal survival (%) 120 100 80 a a a 60 40 20 b ab b b SCA+ BCOA ab P 8500 PI 550610 0 SCA Aphid treatment BCOA+

Developmental time for SCA and GB on P 8500 and PI 550610, both alone and together (BCOA+ and SCA+) Developmentlal time (days) 10 8 6 P 8500 PI 550610 a ab b b a a SCA+ BCOA+ 4 2 0 SCA Aphid treatment

Reproductive performance of SCA and GB on P 8500 and PI 550610, both alone and together (BCOA+ and SCA+) 12 -day fecundity (no. nymphs) 100 80 a a 60 b P 8500 PI 550610 b c 40 20 0 SCA+ d d c BCOA+ 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