病害IPM.ppt

* 1.3 Assessment of disease intensity Introduction and definitions Methods for assessing disease intensity Methods for analyzing disease records Methods for presenting disease records Concluding remarks Why do we need (want) to assess disease intensity?orWhat are the uses of disease intensity records For making decision concerning disease management For quantifying the effect of the pathogens on the host plant and on yield For determining the efficacy of various control measures (pesticides, genotype resistance, agronomic measures, etc.) For verifying the quality of agronomic products and seed Methods to assess disease intensity Disease incidence: The proportion of infected host units, out of the total units sampled 4/10*100=40% 4/10*100=40% Methods to assess disease intensity Disease severity: The proportion of infected part (or the infected area), in each of the sampled units (60+10+30+1)/10*100=10.1% 60 10 30 1 0 0 0 0 0 0 Percentage scale (0-100%) 4 2 2 1 0 0 0 0 0 0 (4+2+2+1)/10*100=0.9 Index scale (0-4) What is better: to assess disease incidence or to assess disease severity? What is easier? What is less subjective to errors? What represents better the effect of the pathogen on the host? Can disease incidence records be converted to disease severity ? 100 Disease incidence (%) 0 Disease severity (%) 0 100 50 50 Disease incidence (%) 0 100 Disease severity (%) 0 10 50 5 What scale to use in the assessments? Number of infected blossoms in a blossom-cluster Number of infected blossoms in a blossom-cluster, out of the total number of blossoms in that cluster Number of infected blossom-clusters in a tree Number of infected blossom-clusters in a tree, out of the total number of blossom-clusters in that tree Sampling unit: a tree Sampling unit: blossom-cluster The number of trees with infected blossom-clusters Number of trees with infected blossom-clusters out of the number of trees in the orchard Sampling unit: an orchard Which part of the