Comparison of grass seed cleaning methods to reduce <i>Anguina funesta</i> seed gall infestation in <i>Lolium multiflorum</i> seed lots

Annual ryegrass (Lolium multiflorum) is a forage and cover crop that is grown for seed in the Willamette Valley of Oregon before being exported globally. The seed gall nematode (SGN), Anguina funesta, is a plant-parasitic nematode affecting annual ryegrass in this seed production region and its detection in seed lots frequently results in rejection by international trade partners. Seed galls are similar in size to healthy annual ryegrass seed and difficult to separate in the cleaning process. In this study, two types of seed cleaners, an air screen and a gravity table cleaner, were evaluated for their ability to remove seed galls from infested annual ryegrass in commercial seed lots. For both cleaners, four air speeds were evaluated on two replicate samples from two commercial seed lots. The air screen cleaner removed galls from healthy seed at a range of airspeeds, but mid-range air speeds led to the highest reduction in galls with the lowest loss of clean seed (120 CFM). The gravity table was highly effective at separating galls from healthy seed, leading to significant gall reductions across clean cuts for three of four tested air speeds (40-172 CFM). This study indicates that seed cleaning is a useful tool for mitigating seed gall nematode infection of annual ryegrass seed. By reducing the risk of seed lot rejections and lowering initial inoculum in saved seed, seed cleaning can help protect Oregon’s grass seed industry from this pest.