9.1 Virulence
Bioassay
9.1.1 Petri Plate
Bioassay
Materials Required
l
Petri dish.
l
EPN (IJs).
l
Whatman No. 1 filter paper.
l
Test insects (larvae).
Procedure
1. Place a moist Whatman No. 1 filter paper in sterile 9 cm
diameter petri dish.
2. Adjust the nematode concentration to 10, 20, 30, and
40 IJs/larva.
3. Use healthy and uniform sized laboratory reared larvae of test
insect for bioassay.
4. Different larval stages can be used for the study.
5. Place 1 ml nematode suspension of 10, 20, 30, and 40 IJs/larva
on the moist filter paper lined in the petri dish.
6. Keep ten larvae of test insect per petri dish.
7. Replicate each set of treatment thrice.
8. Use only 1 ml of distilled water in control plate with test insect
larvae.
9. Provide the insects with their natural food.
10. Cover the petri dish with lid.
11. Incubate the inoculated plates at 25
C.
12. Check the insect mortalities after 24, 48, 72, and 96 h of
inoculation.
13. Correct the mortality data using Abott’s formula [200].
Corrected%mortality ¼
Per cent mortality in treatment À Per cent mortality in control
100 À Per cent mortality in control
 100
14. Analyze the corrected percent mortality data on the pattern of
completely randomized design using three way tables.
9.1.2 Sand Column
Bioassay
Requirements
l
Petri dish.
l
EPN (IJs).
l
Sterile sand.
l
Test insects (larvae).
Procedure
1. Take 1 kg sterilized moist soil into a plastic/glass jar/polyvinyl
chloride tube for testing.
Methods of Bioassay
109