Effects of agro-pedo-meteorological conditions on dynamics of temperate rice blast epidemics and associated yield and milling losses.

2017 - Field Cops Research, 212, 11-22
Bregaglio, S., Titone, P., Hossard, L., Mongiano, G., Savoini, G., Piatti, F.M., Paleari, L., Masseroli, A., Tamborini, L.


Rice blast disease is a threat for European rice growers, who apply chemical treatments each year to limit itsimpact on rice yield and milling quality. Good agronomic practices such as varietal choice and reduced nitrogenfertilization can also be effective in limiting the impact of the disease, which largely varies across sites andgrowing seasons. Here we present a three-year experiment (2013–2015), in which blast disease severity wasdynamically sampled on four varieties grown with two nitrogen doses (standard and double farmer fertilization)in three sites located in Northern Italy (i.e., the largest European rice district). No chemical treatments wereapplied on these experimental plots, which were compared to blast-treated controls. Field yield and yield aftermilling (t ha−1) were measured to assess the impact of rice blast. Disease progress curves of leaf and panicle blastwere analyzed via F-test for site, nitrogen dose, rice variety, and year. The areas under disease progress curveswere correlated with yield losses via linear regression. Finally, a 4-way analysis of variance was performed usingfield yield losses and head rice yield as dependent variables.
Results: Blast epidemics were significantly affected by all the factors considered, with rice variety and year as themost important sources of variability. Areas under disease progress curves were significantly correlated withlosses infield yield and even more in yield after milling, with panicle blast proving to be the most impactfulsymptomatology. Year and variety rankedfirst and second among the factors explaining yield losses, both infield and after milling. These results confirm the effectiveness of varietal choice to reduce blast impact, in-dicating that fungicide applications should be conditional to the conduciveness of weather conditions.

Keywords: Disease severity, disease progress curves, field yield, head rice yield
DOI: 10.1016/j.fcr.2017.06.022