Evidence of a Sexual Life Cycle in Sugarcane Aphid

Gregory Bryan WilsonDr. David L. Kerns

Louisiana State UniversitySorghum – Sugarcane Aphid Research Exchange Meeting

New Orleans, LAJanuary 7 – 8, 2016

Introduction1. In the United States, SCA are generally

considered to be obligate anholocyclic, as no sexual forms have been observed and reported.

However,2. Reported observations of oviparous adults,

sexual reproduction, and eggs do exist.

3. A sexual cycle could help explain the rapid host shift away from sugarcane.

BackgroundHistorically reported as • Aphis sacchari - 1897 - ~ 1970 • Longiunguis sacchari - ~1910 - ~ 1980 • Melanaphis sacchari - ~1980 to present

In 1974, Chaudhuri and Banerjee officially synonymized both L. sacchari and A. sacchari as Melanaphis sacchari (Zehntner) which unified the nomenclature.

Roy Chaudhuri, D.N., Banerjee, C., 1974. A study of the genus Melanaphis (Homoptera: Aphididae) with descriptions of new taxa from India. Orient. Insects 8, 365–389.

Anholocyclic Species

Viviparous females(winged and wingless)

Viviparous females(usually overwinter as

apterae or nymphs)

SUMMER

WINTER

Anholocyclic Overwintering

Historical OW hosts:• Miscanthus sacchariflorous• Andropogon spp.• Pennisetum spp.• Panicum spp.

In U.S., theorized to OW as viviparous morph on Johnson grass, possibly on:• whole plants in tropical zone• rhizomatous tissue or host surviving winter

in temperate zone

Initial Testing

Rhizomatous tissue no-choice test for sorghum isolates• 10 day survey• 3-4 in Johnson grass rhizome• 1 leaf blade with ~50 aphids • After 3 days no aphids survived• Needs further testing

Holocyclic Literature1. Wang, Y.S., 1961. Studies on the sorghum aphid,

Aphis sacchari Zehntner. Acta Entomol. Sin. 10, 363–380.

2. Yadava, R.L., 1966. Oviparity in sugarcane aphid, Longiunguis sacchari Zehnt. (Aphidae: Homoptera). Curr. Sci. 1, 18.

3. Setokuchi, O., 1975. Ecology of Longiunguis sacchari (Zehntner) (Aphididae) infesting sorghums. II. Observations on the oviposition. Proc. Assoc. Plant Prot., Kyushu 21, 8–10.

4. David S.K., Sandhu G.S., 1976. New oviparous morph of Melanaphis sacchari (Zehntner) on sorghum. Entomologist's Record, 88(1):28-29.

Composite Key Learnings• Oviparae appear after 16th generation

(Wang)• Found Nov – Dec and Feb – Mar.• Between 30º – 41º latitude • Oviparous morphs were numerous and

conspicuous• Average temperature 17.7º C• Photoperiod 11:13 – 10:14• Eggs found on Sorghum bicolor

(Sorghum vulgare) and Miscanthus sacchariflourus

• 3-5 eggs per clutch (Setokuchi)

Thank you

Questions? Feel free to contact Greg Wilson at gbwilson@agcenter.lsu.edu