A New Greenbug Biotype1

‘Amigo’, a wheat (Triticum aestivum L. em Thell.) germplasm line resistant to the greenbug [Schizaphis graminum (Rondani)], and selections from crosses and backcrosses of wheat to Amigo were evaluated for resistance to greenbug collections made each year from 1977 to 1980. Amigo, its derivatives, and ‘Insave’ rye (Secale cereale L.) were resistant to these field collections of biotype C greenbugs until January 1980 when Amigo and Amigo derivatives failed to survive a greenbug infestation of progeny of a November 1979 field collection at Bushland, Tex. A series of 11 laboratory tests of biotype C‐resistant and C‐susceptible small grain and sorghum [Sorghum bicolor (L.) Moench] lines infested with either biotype C or the Bushland collections clearly showed the Bushland greenbug to be other than the A, B, or C biotype. The Bushlandarea greenbug was designated biotype E. Insave rye, ‘Will’ barley (Hordeum vulgare L.), and biotype C‐resistant oats (Avena sativa L.) were resistant to biotype E. ‘Largo,’ an amphiploid of T. turgidum/ T. tauschii, appeared to have useable resistance for breeding biotype E‐resistant wheats. Sorghum lines possessing biotype C resistance from tunis grass [Sorghum virgatum (Hack.) Stapf] PI 38108 were susceptible, but sorghums PI 220248 and ‘Capbam’ were resistant to biotype E and should be useful sources of resistance. Biotype E was the predominanbt iotype in all greenbugc ollections made at Bushland, Tex., between November 1979 and August 1980. Biotype E was found 75 miles north of Bushland in May 1980.