Susceptibility of Texas, Kentucky, Canada, and Selected Hybrid Bluegrasses to Greenbug Biotypes ‘E' and ‘F'.

The greenbug, Schizaphis graminum (Rondani), can be a serious pest of wheat, Triticum aestivum L., and other small grains in the southern Great Plains of the USA.  Texas bluegrass (Poa arachnifera Torr.) is a perennial cool-season grass and because of its heat tolerance and persistence in this region, it is of particular interest for development as a quality forage plant.  In an effort to determine the susceptibility of Texas bluegrass to greenbug, biotypes ‘E’ and ‘F’, the predominant biotype found in this region and a type known to infest bluegrass, respectively, were used for screening.  Twenty five Texas bluegrass genotypes, three Kentucky bluegrass (Poa pratensis L.) genotypes, a Canada (Poa compressa L.) genotype, two Texas x Kentucky hybrids, and a Texas x Canada hybrid were screened.  Biotype E, F, or both were capable of reproducing and causing damage to plants of all species and hybrids screened.  On the basis of higher aphid numbers, biotype E had a higher reproduction rate as compared with biotype F on Texas bluegrass.  Significant differences in damage to both biotypes were found among Texas bluegrass genotypes. Some genotypes (9/25 biotype E; 13/22 biotype F) did not support greenbug population growth.  Both Canada and Kentucky bluegrass where highly susceptible to biotype F and interspecific hybrids varied in their damage response with both biotypes. Controlled crosses and progeny screening with Texas bluegrass are planned in an attempt to determine the genetic control of resistance in order to maximize breeding efforts.