| Abstract/Contents: | "A survey was conducted to characterize plant parasitic nematode communities associated with centipede and St. Augustine turfgrasses in urban ecosystems. To date, 135 lawns in East Baton Rouge Parish, LA, have been sampled. Soil types ranged from clay to sandy clay loam, with the average type being loam (30% sand, 20% clay, 50% silt). Twelve nematode genera were identified from soil and root samples of St. Augustine lawns: Criconemella occurred in 91%, Gracilicus in 3%, Helicotylenchus in 94%, Hemicycliophora in 2%,Hoplolaimus in 5%, Meloidogyne in 46%, Pratylenchus in 35%, Scutellonema in 2%, Trichodorus in 3%, Tylenchorhynchus in 25%, Tylenchus in 92%, and KXiphinema in 15%. Respectively, average nematode densities per 250 cm3 of soil were 159, 20, 180, 11, 8, 54, 29, 11, 14, 25, 149, and 11. Ten nematode genera were identified from soil and root samples of centipede lawns; Criconemella occurred in 86%,Helicotylenchus in 78%, Hoplolaimus in 25%, Meloidogyne in 25%, Pratylenchus in 69%, Scutellonema in 3%, Trichodorus in 14%, Tylenchorhynchus in 19%, Tylenchus in 92% and Xiphinema in 6%. Respectively, nematode densities per 250 cm3 of soil were 290, 186, 18, 52, 59, 25, 9, 32, 132, and 14. Nematode genera identified from the survey were used to establish microplot trials to evaluate the impact of grass species and soil type on nematode reproduction and pathogenicity. Treatments in microplot trials for 2012 included three soil types (clay [25% sand, 40% clay, 35% silt], loam [45% sand, 25% clay, 30% silt], and sandy loam [75% sand, 10% clay, 15% silt]), three nematode infestation levels (0, 1^D#x, and 10^D#x nematodes) containing seven nematode genera (the 1X infestation rate contains 15 Pratylenchus, 12 Meloidogyne, 65 Helicotylenchus, 164 Tylenchorhynchus, 665 Criconemella, and 88 Tylenchus) and the two grass species. Nematodes did not significantly impact turfgrass growth at densities used in the 2012 experiment. However, both grass species grown in sandy loam soil had significantly lower foliar weights and total plant weights (p < 0.05) than those grown in the other two soil types. At 220 days after establishment, nematodes increased 50- and 8-fold, respectively, from the low and high infestation levels on St. Augustine. Similarly, there were 25- and 7-fold community increases, respectively, on centipede. In general, Meloidogyne spp. had the greatest reproductive value (R where R= harvest community density/ infestation level). Across all soil types, reproduction of Pratylenchus was greater on centipede than on St. Augustine. Across both turfgrass species, reproduction of Tylenchorhynchus was greater in microplots containing the clay and loam soil types than those containing the sandy loam soil type. Microplot studies currently in progress employ significantly higher infestation levels than those in 2012." |
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