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Developmental dynamics of the Northern root-knot nematode (Meloidogyne hapla) in Washington State vineyards

Katherine East: Washington State University

<div>The Northern root-knot nematode, <em>Meloidogyne hapla,</em> is an economically-important soilborne pest in Washington State wine grape vineyards. There is limited information available on the biology of this nematode upon which to base management decisions, such as appropriate timing for chemical management tactics. The objective of this study was to determine when vulnerable life stages of <em>M. hapla</em> are present in Washington vineyards to improve the timing of management intervention. Prediction of when these time periods occur can be accomplished based on heat accumulation in soil. Two different commercial vineyards with <em>M. hapla</em> were sampled from 2015 to 2017 (March to March). Soil samples were collected weekly during the growing season and monthly from October to March to determine densities of infective second-stage juveniles (J2), eggs of <em>M. hapla,</em> and fine root tips of grapevine. Life stages were considered within the context of soil growing degree days calculated from a base temperature of 0°C (GDD<sub>soil</sub>) starting in March. <em>Meloidogyne hapla </em>has a single generation per year, with J2 density peaking over the winter (4291-4881 GDD<sub>soil</sub>), then declining to a low density in late June to early July (1895-2379 GDD<sub>soil</sub>). Egg density peaked in late July to August (2871-3069 GDD<sub>soil</sub>). Similar to the egg peak, fine root tip density peaked at 2379-2871 GDD<sub>soil</sub>. A model for prediction of <em>M. hapla </em>J2 development in Washington wine grape vineyards based on GDD<sub>soil</sub> will be presented.</div>