Developmental Dynamics of in Washington Wine Grapes.

is the most prevalent plant-parasitic nematode in Washington state wine grape vineyards. Understanding the developmental dynamics of can improve the timing of diagnostic sampling and nematicide application. Three vineyards in Washington were sampled March 2015 to March 2017 to determine the developmental dynamics of by measuring second-stage juveniles (J2) in soil, eggs and adult females in roots, and fine root tips. A model of J2 development based on soil growing degree days using a base temperature (T) of 0°C (GDD) and a start date of 1 March was developed. This model was validated at two additional vineyards in Washington and was robust with values > 0.74. has one generation per year and overwinters primarily as the J2 infective stage. Juvenile populations declined after 1 March, reaching their lowest density in early July and reaching a maximum density over the winter. egg and root tip densities reached a maximum in early August. The number of females per root tip did not vary throughout the year. A single generation with defined peaks in J2 population densities will allow for specific timing of nematicide interventions.