Good day, all. In a biocontrol study, we can easily determine disease severity by using a disease scale developed for a particular plant disease.
On the other hand, disease incidence measures the percentage of plants infected by the disease.
So, I have completed a glasshouse experiment for 84 days and I want to determine the disease incidence. However, based on the disease scale, all my plants treated with biocontrol agents show mild wilting symptoms whereas plants challenged with pathogen alone (control treatment) show complete wilting.
Based on the definition of disease incidence, this means my biocontrol-treated plants are infected (still show mild wilting) and the disease incidence would be 100% which is the same as the control treatment.
I am not entirely sure if disease incidence can be utilized as a parameter in a biocontrol study. Can someone help to clarify this?
Thank you in advance.
You can use a scale based on the percentage of leaves withered, for example, 10% ,15% , and so on, and then use the formula to calculate the disease severity.
where DSI (%) = [sum (class frequency × score of rating class)]/[(total number of plants) × (maximal disease index)] × 100.
Best regard.
Dear Sir,
you can use a scale based on the disease severity, for example:
scale disease severity in % disease severity media
0 0 0 %
1 1-5 2.5 %
2-3 6-10 7.5 %
4 10-35 20 %
5 36-75 50 %
6 76-99 80 %
7 100 100 %
If you have more than one plant per plot you can calculate the media per plot by the following formula:
% disease = sum (n*v)*100/N*V
where:
n - nuber of observations of a certain value of the scale
v medium value in % of a certain value of the scale
N - total number of observations
V maximum value of % of the disease.
VERY IMPORTANT:
Remember that scale values in plant pathology dont have a normal distribution so you have to transform the raw data previously if you want to calculate ANOVA.
You could use the following transformation formula:
Y = arc sin (Srqareroot of X)
being X - medium of disease incidence on each plot.
Good luck with the work .
I am boring on the topic of disease rating, because the longer you study disease, the more important the topic becomes to you. In one disease I study (boxwood blight), I could spend a lot of time determining % leaf area with lesions. However, the diseased leaves tend to drop off no matter what the size of the lesion, so I simply count the number of diseased leaves out of total leaves. In another disease I study (powdery mildew of squash), the total lesion area is correlated with the altered metabolism of the plant and subsequent yield, so % leaf lesion is appropriate. In your situation, you need to ask yourself how much transpiration is affected in partially wilted plants, and whether those plants will eventually become fully wilted.
You can use scale of disease severity that depend on the disease itself
- Badges
- Science topic
- Similar topics
- Biological Science
- Biota
- Eukaryota
- Fungi