New Source of Southern Chinch Bug (Hemiptera: Lygaeidae) Resistance in a Diploid Selection of St. Augustinegrass

Over 400,000 ha of St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, are managed as a turfgrass in the southern United States, and the southern chinch bug, Blissus insularis Barber, is its most important insect pest. New sources of host plant resistance to southern chinch bugs became necessary due to the development of virulent populations of chinch bugs which were able to feed on the only acceptable resistant cultivar, Floratam. Initial testing evaluated 14 lines for chinch bug resistance using insects collected from five locations from Palm Beach Co., FL. Host plant resistance was determined by mortality of adult chinch bugs held on a turfgrass for 14 d. A second study was conducted with five lines from the first test with southern chinch bugs collected from nine locations throughout Florida. Tests showed a high level of southern chinch bug resistance in NUF 76, NUF 216 and FX-10. Leaf blades of NUF-76 are significantly shorter and narrower than other tested St. Augustinegrass lines when evaluated 2 wks after mowing. NUF-76 is unique because for the first time, resistance to the southern chinch bug has been identified within a diploid line of St. Augustinegrass. Prior to this, southern chinch bug resistance was only associated with polyploid lines which generally have large leaves and reduced or no seed set due to sterility problems. This discovery will allow chinch bug resistance to be more easily bred into other St. Augustinegrass lines.