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

Section 4 • Integrated Insect and Rodent Pests Management
methodology
• Field walks, hands-on, and brainstorming
steps
1. Divide participants in small groups and ask them to conduct field walks and observe organicallygrown
vegetable crops showing relatively moderate to serious common cutworm infestation
and NPV-infected common cutworm larvae in learning and adjoining fields. Take note of
presence and number of healthy and NPV-infected common cutworm larvae, other insect pests,
and natural enemies. Interview other farmers, if necessary. List down all observations related
to pest and natural enemy activity and occurrence, crops infested, degree, and characteristic
damage, among others.
2. Facilitate each group to collect NPV-infected common cutworm larvae and to do actual massproduction,
and spraying of prepared NPV solution against common cutworm larvae when
relatively moderate to serious infestation and NPV-infected common cutworm larvae are
observed on organically-grown vegetables in learning and adjoining fields. Below are some
pointers on how to detect and collect NPV-infected common cutworm larvae from organicallygrown
vegetables:
5 Healthy larvae feed at night and conceal themselves in soil during daytime. Infected larvae
feed less, become sluggish and remain on leaf surface exposed to sunlight. The larvae
weakens, stops feeding, and finally dies. The tissues of larval host become digested, body
bursts or milky-white or brown body contents ooze out.
5 Dead but firm NPV-infected larvae are collected into a receptacle. Leaves with ruptured
cadavers are cut using a pair of scissors. Later, these are washed-off with water and mixed
with intact ones before storing in a freezer. It is necessary to know the number of collected
larvae for proper dilution of NPV suspension.
5 Field-collected NPV-infected cutworm larvae are placed in plastic containers with cap and
stored inside a freezer to prolong shelf life and its infectivity. Infected larvae disintegrate so
it is not possible to count desired number for mixing or preparing spray solution.
5 In order to offset this problem, the following may be done: If there are 100 larvae, for
instance, in a container, add water to fill container to one-fourth of a liter. The suspension
will give an equivalent of one larva per milliliter of solution or 4 larvae per tablespoon (10
mL per tablespoon).;
5 The virus suspension is sprayed on leaves of vegetable crops just like ordinary foliar
insecticide. Ten to 15 infected larvae per 16 liters of water (one tank load) are needed.
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