Field Guide of Discovery-based Exercises for - Aseanipm ...

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Field Guide of Discovery-based Exercises for Organic Vegetable Production
5 For best results, spraying should be done in afternoon so that virus can be acquired by larvae,
which feed at night. About 20-30 tank loads, depending on growth stage of crop, are applied
per hectare. Spraying is repeated after two to three weeks depending on density of larvae.
5 Starting from five days after spraying, moribund and dead cutworm larvae can be seen on leaf
surfaces or hanging from underside of leaves. Infected larvae can be collected and placed
in a clean container. This can be used for next spraying or kept in a freezer for future use.
5 Take note of all relevant observations and experiences during this activity.
3. Go back to processing area every week for three consecutive weeks thereafter; brainstorm
in small groups and present output to big group. Conduct participatory discussion to allow
sharing of experiences among participants and facilitators. Motivate farmers to share their
experiences in using NPV to control common cutworms at relatively moderate to serious
infestation levels. Relate shared experiences to effect of NPV on natural enemy populations.
4. After three weeks, synthesize and summarize output of small groups into one big group output.
Draw up conclusions and recommendations from this exercise. If farmers’ cooperatives or
organizations wish to mass-produce cutworm-NPV at farm-level for use of their members, they
may adapt the following procedure:
a. mass-rearing of Cutworm (Spodoptera litura)
5 Collect just enough leaves of taro, sweet potato, castor or mulberry plants.
5 Place cutworm egg-mass on a leaf secured in a plastic cup with water.
5 Replace food as often as necessary by cutting leaf with cutworm larvae, putting them
on another fresh leaf, and adding water on plastic cup.
5 When leaf feeding of cutworm larvae (e.g., full grown) ceases, transfer them in plastic
container filled with moistened sand as medium.
5 After 7 days, collect cutworm pupae in the moistened sand.
5 Place pupae in plastic container and finally inside an insect cage.
5 Place Petri dish with 10% sugar solution inside insect cage as food for emerging
cutworm moths.
5 Place also fresh taro, sweet potato, or mulberry leaves inside insect cage as egg
deposition sites for female cutworm moths.
5 Collect cutworm egg-masses and repeat mass-rearing procedure.
B. mass-production of NPV (Nuclear polyhedrosis virus)
(a) Identification, Collection, and Preservation of NPV-infected Cutworm Larvae