Abstract

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is host to the southern chinch bug (SCB) (Blissus insularis Barber).  This study evaluated and compared field and laboratory resistance of St. Augustinegrass germplasm to the SCB.  Turf field plots of 20 St. Augustinegrass genotypes were monitored monthly for 2 years for damage by the SCB.  After each occurrence of damage, plots were treated individually with an insecticide and allowed to become damaged again.   Genotypes differed in frequency of damage, which varied from 1.02 occurrences per year for FX-22 and FX-338 to zero occurrences per year for 'Floratam'.  During the next 2 years when no insecticide was applied, the portion of dead canopy varied from 86% for FX-313 to 0% for 'Floratam'.  In a second field experiment, SCB damage was evaluated in 10 polyploid St. Augustinegrass genotypes.  Damage varied from 90% for 'Bitterblue' to 0% for 'FX-10'.  Oviposition rate was determined from SCB confined in the laboratory on genotypes from both field experiments.  Oviposition rate differed among genotypes and predicted (P < 0.01; r² = 0.67 to 0.79) field damage.  To my knowledge, this is the first report of field resistance to the SCB in St. Augustinegrass,validating the use of laboratory bioassays.