Plant-parasitic nematodes cause millions of dollars in economic loss each year in the state’s $104.7 billion food and agriculture industry. In potato production, the root-lesion nematode, Pratylenchus penetrans, can synergistically interact with the wilt-inducing fungi Verticillium dahliae, causing a disease known as Potato Early Die (PED). This disease complex causes plants to senesce 4 to 6 weeks early, thereby causing yield losses between 30% to 50%. The industry standard for PED management is soil fumigation and applications of post-planting pesticides, nonetheless, current management practices are not sustainable, and PED remains one of the top industry priorities in Michigan potato production. Therefore, this Ph.D. dissertation investigates different sustainable management strategies to manage PED with a focus on manure-based amendments and biological control agents, emphasizing the importance of preserving soil health. For the first objective, the effectiveness of integrated management of PED with manure-based amendments and biological control agents was determined under field conditions. The results show that the most effective management alternatives for P. penetrans control are raw poultry manure, both standalone and in combination with a singular application of Vydate® or MeloCon® (Purpureocilium lilacinum), and Compost A in combination with a singular application of MeloCon®. It was also found that Compost A, a composite of composted raw poultry and cattle manure with wood ash, resulted in higher yields underscoring the necessity of selecting amendments based on their potential to mitigate pathogen prevalence or augment productivity. For the second objective, the effectiveness of the management of PED with non-fumigant nematicides, fungicides, and seed treatments was determined under field conditions. The results show that Vydate® is the most effective nematicide to control P. penetrans, while the treatment combination Velum®+Velum®+Movento®+Movento®+Vydate® showed a slight decrease of V. dahliae stem infection of 6%. As for the third objective, commercially available biological control agents for Michigan Verticillium dahliae management were identified. The results show that the active ingredients of Tenet® (Trichoderma asperellum and T. gamsii), Actinovate® (Streptomyces lydicus), and Elatus® (azoxystrobin and benzovindiflupyr) are highly antagonistic to the three evaluated V. dahliae isolates in-vitro. However, greenhouse trials suggest that Actinovate® delivers the most effective control of Michigan V. dahliae isolates. Finally, for the fourth objective, the influence of manure-based amendments on potato soil microbiome and its correlation with P. penetrans abundance was determined. The results from the greenhouse trials showed that P. penetrans abundance in manure-treated soils was significantly lower than the control, independent of the manure amendments autoclaving process. The relative abundance of soil bacterial and fungal phyla and the ɑ- and ß-diversity indices of bacterial and fungal species changed in response to both autoclaved and non-autoclaved manure amendments and trends were different between the two experiments. With the addition of manure amendments only in the second experiment did the relative abundance of the Firmicutes bacteria phyla significantly increase and negatively correlate with P. penetrans abundance. Disease complexes like PED are understudied and hence challenging to manage, but the evidence provided by these studies about management alternatives for P. penetrans and V. dahliae separately is essential due to their important roles in the PED disease complex. Disease complexes often require an integrated management approach to ensure maximum control of primary inoculum. Therefore, crop rotation with non-hosts, weed, irrigation, and nutrient management coupled with before planting soil incorporation of raw poultry manure, early season application of Vydate®, and applications of biological control agents like P. lilacinum and S. lydicus can mitigate the detrimental effects of PED, foster soil health and ensure sustainable agricultural practices.
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