ABSTRACT
Alfalfa is the herbaceous, perennial, deeply rooted legume that supplies high-quality feed. It is mainly used to produce hay and silage, but because of its high forage output, nutritional value, and broad tolerance to various climates and soil types, it may also be used for grazing. It is vulnerable to various infectious diseases caused by biotic agents such as fungi, bacteria, viruses, and mollicutes at different crop development stages. Fungi like Fusarium spp., Rhizoctonia solani, Sclerotinia spp., and oomycetes are the most damaging and frequently occurring biotic agents that significantly hinder crop establishment, degrade the quality of forage, and lower seed and green fodder output. These pathogens also result in indirect losses, such as decreased nodule development in the crop, which lowers its ability to fix nitrogen. Abiotic agents cause noninfectious diseases of alfalfa. The pathogen is not involved in these noninfectious diseases; hence they are not transmissible. Noninfectious diseases include drought, pollution, extreme heat, salt, waterlogging, frost, and winterkill. These noninfectious diseases can be managed by ensuring that alfalfa plants are not exposed to extreme abiotic stresses. Treating infectious diseases involves several control strategies, including chemical and environmentally friendly methods. However, most disease management techniques employ chemicals, which can create environmental concerns and pathogen resistance. This chapter’s goal is to evaluate the current state of biotic and abiotic diseases, disease progression, and frequent symptoms throughout the lifespan of the alfalfa crop.
