Incidence of mal de Rio Cuarto disease and vector infectivity in localities of the endemic and surrounding area, 2020/21

Abstract

The incidence of Rio Cuarto disease in oats and wild grasses, as well as the rate of infected vectors, are useful epidemiological parameters for characterizing the virosis. Fields of oats from the endemic area (Holmberg, San Ambrosio, Chaján, Adelia María, and Huinca Renancó) and from La Pampa were sampled and analyzed by serology. Weeds (Aleppo grass, Cynodon sp. and Bromus sp.), fields of maize in production or in trials of cultivars (cv.), and non-virus transmitting carrier insects were also analyzed. All the batches of oats tested positive for the virus, with incidences of between 3 and 50%. Aleppo was positive in Adelia María (4%), while C. dactylon and B. unioloides from Huinca Renancó, Adelia María and La Pampa were negative. A susceptible batch of maize in La Pampa had a 57% incidence; early trials of cv. in the endemic area recorded an average of 55% (30 to 83.3%), and late trials, 5% (0?10%), corroborating the importance of the date of planting. La Pampa and Holmberg had high rates of infected insects (30 and 25%) while Adelia María and Huinca Renancó recorded 19 and 10%, respectively; in all cases about half were infective. The results are in addition to those of the validation of the disease prognosis system.