In the Comarca Lagunera, located in the North of Mexico, alfalfa is the main forage crop. In this region, crown rot (Fusarium spp, Rhizoctonia solani, Colletotrichum sp, Phoma medicaginis) is the most frequent disease of alfalfa: however the impact of the disease on forage production was unknown. This study was undertaken to estimate the losses caused by this disease on alfalfa of different ages (1, 2 and 3 years after establishment).
Samplings were conducted on representative sites of the area. It was found that crown rot affects alfalfa at any age and that the proportion of diseased plants and the damage increase as the crop ages. Losses caused by crown rot were estimated on 11.6, 28.0, and 33.3% of dry forage in alfalfa of one, two, and three year old, respectively, severely affecting the alfalfa production in the area.