Effect of urban plant debris and soil management practices on plant parasitic nematodes, Phytophthora blight and Pythium root rot of bell pepper

Abstract

Soil management practices were examined for their effects on plant parasitic nematodes and soilborne diseases of field grown bell pepper ( Capsicum annuum). Field plots were established on a diversified organic vegetable farm that had been under certification for 5 years and on a conventional pepper farm that had been fumigated with methyl bromide/chloropicrin and cropped annually to bell pepper for 25 years. The plot design was a split plot where the main treatment was the application of 67 t ha −1 of urban plant debris (UPD), and sub plots were; (1) no-till production into residue remaining from a cover crop of Sunn Hemp ( Crotalaria juncea), (2) or Iron-clay Pea ( Vigna unguiculata), (3) creation of raised polyethylene-mulched beds and, (4) soil solarization for a 6–8 week period. Soil fumigation with methyl bromide/chloropicrin (67/33) was evaluated only at the conventional farm site. Experiments were conducted in 1999 and repeated in 2000. At the organic farm only Pythium root rot was identified whereas, at the conventional farm Phytophthora blight was the predominant soilborne disease. UPD application significantly reduced the incidence of Pythium root rot from 24.7% to 12.1% in 2000 at the organic site and the incidence of Phytophthora blight from 49.8% to 31.1% in 1999 at the conventional site. At the conventional site, Phytophthora blight was significantly lower in solarized (21.9%) and fumigated (22.1%) plots when compared to plots with untreated soil covered by polyethylene mulch (46.1%) in 1999. In 2000, Phytophthora blight was significantly higher in the no-till treatments (91.1–91.8%) when compared to the other soil management treatments (50.2–63.5%). UPD application significantly reduced the populations of plant parasitic nematodes from 64.5 to 37.5 per 100 cm 3 soil in 2000 at the organic site and from 94.3 to 12.9 in 1999 at the conventional site, when compared to treatments not receiving UPD. At the organic site the populations of plant parasitic nematodes were significantly higher in the no-till Sunn Hemp plots than solarized plots. At the conventional site, significantly higher populations of Meloidogyne spp. were found in solarized and no-till Sunn Hemp treatments then in untreated soil covered with plastic mulch, while significant reductions in Meloidogyne spp. only occurred with soil fumigation. The results demonstrate that several nonchemical management practices can reduce the impact of soilborne pests for fresh market bell pepper production in a humid, subtropical climate.