Carrot (Daucus carota L.) and winter wheat (Triticum aestivum) are two important crop systems in Michigan agriculture. Bountiful yields are challenged by a myriad of bacterial, fungal, and viral diseases, herbivorous insects, nematodes, and animals. Particularly, plant-parasitic nematodes threaten yields as damage results in nonspecific symptoms, which can prohibit proper diagnosis. Root lesion nematodes (Pratylenchus spp.) are widespread in North America and are known to infect over 350 crop hosts. Because of their broad host range, typical recommendations for management like crop rotation are obsolete. Additionally, the distribution and abundance of Pratylenchus at the species level is unknown, further exacerbating issues with detection and developing tolerance levels. A series of objectives was established to help fill knowledge gaps and pave a pathway to effective management. During harvest, soil and root surveys were conducted for carrots (early October) and winter wheat (late June) to determine the top plant-parasitic nematode genera. In tandem, individual adult Pratylenchus females were collected for molecular identification from both carrot and wheat fields (N=100). Results indicated that Pratylenchus spp. were the most abundant and widespread plant-parasitic nematodes in both crops, occurring in 100% of carrot fields and 90% of winter wheat fields. Pratylenchus penetrans, P. crenatus, and P. neglectus were the most identified Pratylenchus species, emphasizing the need to investigate relationships with these hosts. Next, under a series of greenhouse trials, the top three Pratylenchus species were inoculated to young carrot and wheat seedlings above the threshold level. Strikingly, P. penetrans and P. crenatus damaged nematode to carrots, eliciting root weight reduction by 36.94% and 21.76%, compared to non-inoculated control plants. P. neglectus did not reduce root weight or taproot length. Contrastingly, P. neglectus was the most damaging nematode in wheat and reduced root weight by 24.07% compared to control plants, while P. crenatus did not reduce winter wheat plant height or root weights. Finally, the grower standard, oxamyl, is a nematicide that may be subject to increased environmental bans. To investigate alternative strategies, such as alternative chemically based nematicides, biologically based nematicides, manure-based compost soil amendments, and cover crop incorporation for managing plant-parasitic nematode populations, we evaluated these strategies under field and greenhouse conditions. Under field conditions, Pratylenchus nematode harvest concentrations applied with biological or chemical nematicides were not significantly different from untreated control plots. In a two-year parsnip field trial, Nimitz and Vydate reduced root-knot nematodes and resulted in higher yields than control plots. Finally, the oilseed radish (cv. Control) was a nonhost to both Pratylenchus penetrans and Meloidogyne hapla, and it may be a suitable dead-end cover crop if field studies support our findings. None of the products effectively treated Pratylenchus-infested carrot fields, highlighting the complexities of this pest system. However, in parsnips, M. hapla populations were sufficiently managed with Nimitz, making this treatment a potential alternative to Vydate. Our studies provide evidence that Pratylenchus spp. are severe pests of carrot and winter wheat plants in Michigan and that species-specific identification of these species is essential in determining when and how to manage them.
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