Comparing the Temporal Development of Wheat Spike Blast Epidemics in a Region of Bolivia Where the Disease Is Endemic

Epidemics of wheat blast, caused the Triticum pathotype Magnaporthe oryzae, were studied in Santa Cruz del la Sierra region Bolivia to quantify and compare temporal dynamics disease under different growing conditions. Six plots a susceptible cultivar planted at Cuatro Cañadas (CC), Okinawa 1 (OK1), 2 (OK2) 2015. Spike blast incidence (INC) severity (SEV) leaf (LEAF) quantified each plot regular intervals on 10 × grid (n = 100 clusters spikes), beginning head emergence (Feekes growth stage 10.5), for total nine assessments CC, six OK1, OK2. increased over time 20 30 days before approaching mean INC 100% SEV 60 75%. The logistic model was most appropriate describing spike blast. highest absolute rates increase occurred earliest OK1 latest OK2, all cases it coincided with major rain events. Estimated y 0 values (initial intensity) significantly (P < 0.05) higher than CC or whereas r L (the rate parameter) OK2 OK1. It took about fewer reach 10, 15, 20% compared CC. Based survival analyses, survivor functions 15 (ts) between other locations, probabilities reaching thresholds being LEAF 21 after Feekes 10.5 had significant effect ts For every 5% LEAF, chance by day 55%.