Nitrogen inputs and irrigation frequency influence population dynamics of Mesocriconema xenoplax under grapevines

Nitrogen (N) fertilization and irrigation are critical for tree fruit and grape production in semi-arid regions of Western North America. Growers are increasingly considering more conservative fertilization and irrigation practices in order to optimize fruit quality while minimizing environmental impacts. The implications for pest populations of such shifts in production practices are not well known and warrant consideration. The objective of this research was to determine the effects of drip irrigation frequency (daily vs approximately every third day) and N fertilizer rate (ranging from 0 to 64 kg N/ha/year) on population densities of the ring nematode, Mesocriconema xenoplax, in a vineyard. The experiment was a split-plot randomized complete block design with irrigation frequency applied as whole-plot treatments and N input applied as subplot treatments. Nematode populations in root zone soils were assessed in spring, summer and fall of 2010 and 2011. There was a significant irrigation frequency × N input interaction, with M. xenoplax population densities increasing with N input under daily irrigation but not under low frequency irrigation. The data suggest that reductions in fertilizer N input and irrigation frequency, that have minimal impacts on fruit quality and yield, can also minimize M. xenoplax population buildup.