Project Title: Impact of Plant Parasitic Nematodes on Grapevine Growth and Development in Washington
Project Duration: 3 years, FY18-20, 1 July 2017- 30 June 2020
Principal Investigator(s): Michelle Moyer, Assistant Professor
Organization: WSU-IAREC, 24106 N. Bunn Rd., Prosser, WA 99350
Email: [email protected]
Decisions for managing plant-parasitic nematodes in Washington wine grapes have been historically made with very little information regarding nematode biology or lifecycle. As the industry enters a time of replanting, and the use of preplant fumigants becomes increasingly challenging due to regulation, knowing how to best manage this pest is paramount for sustainable grape production. This project looked at several key aspects in plant-parasitic nematode biology and management strategies, to build a better understanding of how to best optimize our approaches for reducing vine loss due to nematodes. First, we evaluated three different cultural practices that could be used to mitigate nematode decline in newly-planted vineyards: rootstocks, irrigation, and fertilization (nitrogen). We learned that the biggest impact, in terms of reducing nematode development after planting, is achieved by using resistant rootstocks as the primary cultural practice, rather than the adoption of altered irrigation or fertilizer (nitrogen) regimes to stimulate vine vigor. Second, we continued to monitor a large-scale rootstock trial at a commercial vineyard where we learned that preplant fumigation has a very limited efficacy period (6 months post planting), and that visible decline symptoms of early nematode infestation in a replanted block take up to 5 years to manifest (typically at a time when the vineyard should be reaching peak productivity). This continuing trial is a unique experience, in that we now have a “tool” (a vineyard) to monitor the long-term impacts of nematodes and preplant fumigation on vine establishment and productivity. Trials that are limited to short-term resistance evaluations fail to capture the long-term consequences of chronic exposure to a pest, which is the more common situation in perennial cropping systems. Finally, we continued to evaluate the performance of different post-plant nematicides, where we learned that manufacturer’s timing recommendations were not aligning with nematode biology in this state. Many of the products that targeted the mobile root-knot nematode second-stage juvenile (J2) stage were being applied to late in the spring to have an impact the majority of the J2 populations. Products that were ovicides (targeted to eggs) were labeled to be applied in the spring and fall, but not when eggs are present (mid-summer). These misalignments with target nematode biology may be one of the reasons why past efficacy trials did not look promising – the products were simply not being recommended for the appropriate time when they would be most efficacious.
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