The number of root lesion nematodes (Pratylenchus neglectus) declines after strand medic pasture

Ross Ballard, Jake Howie, David Peck, Nigel Charman, Jeff Hill and Alan Mckay
South Australian Research & Development Institute (SARDI)

Background
Annual medics are widely grown in neutral and alkaline soil regions where they are valued for livestock production, contributions of fixed N to the farming system and for their ability to reduce the impacts of soil borne disease on the cereal and oilseed crops that follow.
There have been conflicting reports in the literature and popular press regarding the impact of medics on the population densities of Pratylenchus neglectus (root lesion nematode, hereafter referred to as Pn). For example, Collins et al. (2013) referred to a greenhouse study as the basis for listing cultivars of burr and barrel medic as susceptible or very susceptible, i.e. likely to result in significant multiplication of the nematode. This is at odds with previous field studies in SA (Ballard et al. 2006) that had shown medics maintained or reduced Pn number.
This field study quantifies Pn numbers following the growth of strand medic (Medicago littoralis), the best adapted and most extensively grown medic in Mallee agricultural regions. It differs from previous field studies in that it considers if changes to Pn multiplication are influenced by the initial (before medic) nematode population density.