New management systems for northern root-knot nematode (Meloidogyne hapla Chitwood Tylenchida: Heteroderidae) in daylily (Hemerocallis spp.) ornamental plant production fields

Michigan has the third largest floriculture industry in the United States, with the production of daylily (Hemerocallis spp.) a top commodity. Daylily is one of the most economically important ornamental plants, yet their production is plagued by plant-parasitic nematodes, especially the northern root-knot nematode, Meloidogyne hapla. Seven treatments in combination with a high-carbon, cow manure compost were selected for a three-year field trial at a commercial nursery in Zeeland, MI to discern the best M. hapla management strategies in daylily field production for its entire production cycle. Treatments included the compost manure by itself, Indemnify as a soil drench and as a pre-plant dip both together and separately, AzaGuard, TerraClean 5.0, and an untreated control. Additionally, a similar multi-year greenhouse trial was conducted and included a new treatment: Majestene 304. Results showed that the high-carbon, cow manure compost + Indemnify as a soil drench by itself and in combination as a pre-plant dip were the most effective treatments in reducing M. hapla population levels; in the greenhouse experiment, Indemnify reduced population levels by 83%. Majestene 304 provided the next best control of M. hapla, yet it had the highest gall ratings; the compost by itself was not effective, having higher M. hapla populations than the control in both experiments. Lastly, both trials emphasize the importance of applying these management strategies every year for the best M. hapla management. These results give the ornamental plant industry new, effective management systems to control M. hapla in ornamental plant field production.