| Effects of Crotalaria juncea, Brassica napus, and Tagetes erecta on suppression of Rotylenchulus reniformis were evaluated in pineapple-cover crop intercycle and intercrop systems.In the intercycle system, cover crops were grown for 3 months, soil incorporated, and pineapple was planted. Crotalaria juncea intercycled plots suppressed the populations development of R. reniformis on pineapple longer than the other cover crops and weedy fallow treatments. Effect of C. juncea suppression of R. reniformis was similar to the 1,3-Dichloropropane (1,3-D) fumigation. However, suppression of R. reniformis population densities by C. juncea was not effective in a 6 year-fallowed soil and a pineapple growing soil in a greenhouse test, possibly due to the poor establishment of nematode-antagonistic microorganisms or the viable R. reniformis population, respectively.In the intercrop system, cover crops were intercropped with pineapple for 2 years, soil incorporated, and previous pineapple and cover crop planting beds were alternated. Both C. juncea and B. napus suppressed R. reniformis population densities more than in T. erecta, weedy fallow, or pineapple planting beds. Prolonged culture of C. juncea in an intercropping system had shown a trend of enhancing nematode-trapping fungi more than that in the intercycle system, and offers greater R. reniformis suppression.Crotalaria juncea is a poor host of R. reniformis and produces allelopathic compounds that suppress R. reniformis mobility and hatch. Soil amended with C. juncea enhanced the population densities of parasitic nematode-trapping fungi in all the soils tested except in soil recently treated with 1,3-D. Enhancement of bacterivorous nematodes by C. juncea indicated that other microbial activities could also be enhanced. B. napus is also a poor host to R. reniformis. Leaf and root leachates are suppressive to R. reniformis. However, B. napus was susceptible to Meloidogyne javanica, another important pathogen of pineapple. T. erecta is susceptible to R. reniformis, has no allelopathic effects on R. reniformis and its amendment only enhanced saprophytic nematode-trapping fungus, a less effective nematode trapper than the parasitic nematode-trapping fungus.Crotalaria juncea is a promising cover crop for R. reniformis management as an alternative to intensive use of nematicides in pineapple production. |
