农业植物病害IPM（英文）- (5).ppt

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=%
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=
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 u