26th Southern Conservation Tillage Conference
Pots were arranged in a randomized complete block design on greenhouse benches, with each of the 10 plant species replicated four times. Plants were watered daily and fertilized weekly with 50 ml/pot of a 0.54 g/L solution of a 15-30-15 (N:P2O5:K2O) fertilizer (Miracle-Gro, Scotts Miracle- Gro product Inc., Marysville, OH). No pesticides were applied, except for an occasional application of Safer Brand Insecticidal Soap (Safer, Inc., Bloomington, MN) for management of whiteflies.
The experiment was harvested by replication from 11-21 December 2003, by cutting plants at the soil surface, and removing, washing, and weighing the root system. Root-knot nematode galls present on each root system were rated on a 0 to 5 scale, where 0 = 0 galls, 1 = 1-2, 2 = 3-10, 3 = 11- 30, 4 = 31-100, and 5 = >100 galls per root system (Taylor and Sasser, 1978). Three grams of the root system was removed from selected plants that showed no galling and stained in a solution (0.15g/L) of Phloxine B (Daykin and Hussey, 1985) to reveal egg masses. Another portion of the root system was used for extraction and incubation of eggs as described above to obtain the number of viable J2 hatched per g of fresh root weight. Total J2 present per root system was also computed. A soil subsample (100 cm3) was removed from each pot for extraction of nematodes.
Data Analysis Data were subjected to analysis of variance (ANOVA). For the field surveys, results of each location were analyzed separately, because host × location interaction was significant (P ≤ 0.05) for some parameters. Analysis was done using the PROC GLM procedure of SAS (SAS Institute, Inc., Cary, NC). Nematode populations in soil or root were transformed by log 10(x + 1) to ensure that the data followed a normal distribution before conducting ANOVA. ANOVA was followed by Duncan’s new multiple-range test to compare means among hosts and blocks at each location in the field survey, or among plant species in the greenhouse test.
RESULTS AND DISCUSSION Weeds frequently encountered at most locations were pigweed, crabgrass, and purple nutsedge (Table 1). Weeds encountered at specific sites were hairy indigo at PSREC, lambsquarters and signalgrass at Rosie’s Organic Farm, and Virginia pepperweed at PSFTL (Table 1). Root-knot nematodes (Meloidogyne spp.) and ring nematodes (Mesocriconema spp.) were encountered at all sites even if at least one member of the population was detected (Table 2).
PSFTL. Lesion nematodes (Pratylenchus spp.) and ring nematodes were the predominant nematodes at this site. Lesion nematode population density was higher (P ≤ 0.05) on Virginia pepperweed than on volunteer cowpea (Table 2). Ring nematode population means were not significantly different between hosts.
Rosie’s Organic Farm. The predominant nematodes at this site were root-knot, ring, and stubby-root (Paratrichodorus sp.). Lesion and lance nematodes (Hoplolaimus sp.) were less frequently encountered and were not included in the analysis. Significant differences among blocks (P ≤ 0.05) were only observed for the root-knot nematode population, with the highest mean for the pepper block (349/100 cm3 soil), compared with the muskmelon (84/100 cm3) and non-crop (53/100 cm3) blocks. Root-knot nematode population was higher (P ≤ 0.05) on purple nutsedge and pigweed than on lambsquarters and signalgrass (Table 2). The population mean for root-knot nematode on crabgrass (3.72/100 cm3 soil) was very low (data not shown). Ring nematodes population densities were higher (P<0.05) on lambsquarters, nutsedge, and signalgrass than on pigweed (Table 2).
Stubby-root nematode population pigweed or signalgrass (Table 2).
means were lower (P ≤ 0.05) on purple nutsedge Comparisons between nematode populations
(mulch) than on associated with