Shifting Prevalence of Plant-Parasitic Nematodes in Orchards and Vineyards of the Okanagan Valley, British Columbia

Fruit production in the Okanagan Valley of British Columbia is dominated by apple, sweet cherry, and wine grape. The relative importance of sweet cherry and grape has increased in recent decades, but little was known of the plant-parasitic nematodes associated with those crops. Soil samples analyzed for plant-parasitic nematodes were collected from a total of 39 apple orchards, 61 cherry orchards, and 57 vineyards; most were collected in 2018, but 36 cherry orchards were sampled in 2012. Soil properties were also assessed and related to nematode population densities. Nematode genera of potential significance were, in order of prevalence, Pratylenchus, Mesocriconema, Xiphinema, Paratylenchus, Paratrichodorus, Hemicycliophora, and Meloidogyne. Pratylenchus were found in 79, 98, and 81% of the apple, cherry, and grape plantings, respectively; Mesocriconema were found in 51, 79, and 82%; and Xiphinema were found in 59, 51, and 77%. Population densities of the three dominant genera were influenced more by soil texture than any other soil characteristics, with Pratylenchus being negatively correlated with percentage clay, Mesocriconema positively correlated with percentage sand, and Xiphinema positively correlated with percentage silt. The high prevalence of Mesocriconema in cherry orchards and vineyards in this region is significant because Mesocriconema is known to be an important pest of other Prunus crop species and grapevines in other regions. This study therefore provides a rationale for increasing grower awareness and research efforts on the impacts and management of Mesocriconema and other plant-parasitic nematodes in orchards and vineyards in the region.