Abstract

A fine-textured, dwarf St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) genotype, FX-313, was severely damaged in plots in the third year of evaluation in sandy soil in southern Florida.  Damage was associated with numerous (>40/100-cm³ soil) sting nematodes, Belonolaimus longicaudatus Rau.  Damage was ameliorated (P<0.01) by fenamiphos applied broadcast at 2.2 g a.i./m², and B. longicaudatus numbers were reduced (P<0.01) compared with untreated plots.  Root dry weights of four diploid (2n = 18) St. Augustinegrasses--(FX-261, FX-299, FX-313, and Seville) were reduced (P<0.001) by B. longicaudatus in a temperature- and light- controlled experiment.  Estimated daily transpiration, an indicator of plant health, was reduced after 112 days to 3.32 g/pot for inoculated plants, compared with 5.10 g/pot for uninoculated plants.   Genotypes did not differ in nematode number per pot (mean 551/215 cm³ soil) 128 days after inoculation, but differed (P<0.05) in nematode numbers on a root dry weight basis, with FX- 313 and Seville representing the extremes, 12,300 and 4,000 B. longicaudatus/g root dry weight, respectively.  The diploid St. Augustinegrasses evaluated were good hosts for B. longicaudatus, but field data and controlled inoculation demonstrated genetic variation in susceptibility.