Weed indices are used to study the effect of weed density, growth, and suppression on crop plants. Common indices include weed infestation, weed index, weed control efficiency, and smothering efficiency. The document defines each of these indices and provides examples of how to calculate them. Higher values of weed control efficiency and smothering efficiency indicate better control of weeds. The weed index compares yields between treated and untreated plots, with lower values showing more effective herbicide treatment.

1. GOLANDAS
BAGHEL
(160111006
WEED INDICES FOR JUDGING THE EFFICACY
OF WEED CONTROL TREATMENTS

2. WEED INDICES
“weed indices are use to study the effect or weed
density growth and suppression effect of weed on
crop plant. The common indices uses for weed
flora study are Weed Infestation, weed index,
Weed control efficiency and smothering efficiency”
The under listed terms provide a logistic support in
impact assessment, interpretations and drawing
appropriate conclusions in weed management
research.

3. To study the weed and crop
response to weed control treatment
To study the efficiency of herbicide
To determine the efficiency of
intercropping system in suppression of
weed
OBJECTIVE OF WEED INDICES

4. • Weed infestation
• Weed index
• Weed control efficiency (WCE)
• Weed smothering efficiency (WSE)
• Weed persistence index (WPI)
• Crop resistance index (CRI)
• Pest (weed) management index (PMI or WMI)
• Agronomic management index (AMI)
• Treatment (Herbicide) efficiency index (TEI)
• Weed intensity
Different weed indices

5. WEED
INFESTATION
It refers to the percentage of weeds in
the composite population of weed and
crop plants.
Total number of weeds in an unit area
Total number of weed and crop
plants in the same area
×100
WI (%) =

6. WEED INDEX
Weed Index =
It refer to the reduction in crop yield due to
the presence of weed in comparison to
weed-free plots.
Yield from weed free (hand weeded) plot-
yield from treated plot
Yield from weed (hand weeded) plot
This is used to assess the efficacy of a herbicide.
Lesser the weed index, better is the efficiency of
a herbicide.

7. WEED INDEX COUNTI..
Example: Calculate the weed index for atrazine and
simazine applied in the maize from the following data:
1. Yield of maize from weed free plot = 20 q/ha
2. Yield of maize from atrazine treated plot = 1 8 q/ha
3. Yield of maize from simazine treated plot = 19 q/ha
Calculation
20 - 18
20
1.) Weed index for
atrazine = X 100 =10%

8. 2.) Weed index for
simazine =
20 - 18
20
x 100 =10%
Result:
The weed index is less (5%) for
simazine, compared to atrazine (10%).
Therefore, simazine to be applied in
maize for effective control of weeds.

9. Weed Control Efficiency (WCE):
It indicates the percentage reduction in weed
population or dry weight of weeds under treated plot
(herbicide) in comparison to untreated plot (weedy).
This index is used to compare the different weed
control treatments. It is also known as Weed Control
Index (WCI). Higher the WCE, better is herbicidal /
weed control treatment.
WCE (%) =
Weed count in unweeded plots - Weed count in treated
plots
Weed count in unweeded plots
X 100
Dry matter of weeds in unweeded plots-Dry matter of weeds
treated plots
Dry maUer of weeds in unweeded plots X 100

10. Example :
In a weed control experiment in wheat
crop, dry-weight d weeds in un weeded plots
was 500 kg/ha, whereas in isoproturon and
metsulfuron treated plots, it was 250 and 150
kg/ha, respectively. Find out the WCE and
report which one herbicide in better
Solution
1.) WCE for isoproturon = 500 – 250
500
X 500 = 50%

11. 2.) WCE for metsulfuron =
500 – 150
500
X 500 = 70%
Result
Since the WCE of metsulfuron is
higher (70%) than that of isoproturon
(50%), so metsulfuron is better than
isoporoturon in controlling weeds in
wheat crop.

12. Weed Smothering Efficiency
(WSE):
This index is used to determine the effect
intercropping on suppres­sion of weeds in comparison
to sole crop stand .
WSE (%) =
Weed dry weight in sole crop stand plots - Weed
dry weight in intercropped plots
Dry matter of weeds in sole crop stand
X 100

13. Pest (weed) management index :
(PMI or WMI)
 Agronomic management index (AMI)

14. Weed persistence index (WPI)
Crop resistance index (CRI)

15. Treatment (Herbicide) efficiency index:
(TEI)
 Weed intensity:

16. References:
 Practical manual of weed science by Kewat M.L. and
Sharma R.S.
 Principles of agronomy by Reddy And Reddy.
 Modern concepts and advance principles in crop
production by Panda S.C.
 Fundamentals of Agriculture by Arun Katayan.
 Hand Book of Agriculture by ICAR New Delhi.

17. Thanking you for
………………….patience hearing