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

learning objectives
210
Field Guide of Discovery-based Exercises for Organic Vegetable Production
• To make participants aware of and understand the role of Diadegma parasitoid in managing
population of DBM in organically-grown crucifers; and
• To learn and do hands-on of ‘pulling the guts’ technique in determining degree of DBM larval
parasitism by Diadegma in farmers’ field.
materials
• Office supplies (e.g., Manila papers notebooks, ball pens, marking pens, and crayons);
• Other supplies (e.g., hand lenses, soft brush for collecting specimens, plastic jars, syringe, vials,
and denatured alcohol); and
• Organically-grown crucifers in learning and adjoining field showing early infestation of third
and fourth instars DBM larvae.
methodology
• Field walks, hands-on, and brainstorming
steps
1. Divide participants in small groups and ask them to conduct field walks, observe organicallygrown
crucifer crops showing early infestation of DBM in learning and adjoining fields. Take
note of feeding characteristics of pest. Interview other farmers, if necessary. List down all
observations related to pest occurrence, degree of parasitism and characteristic of pest damage,
etc.
2. Facilitate each farmer to do hands-on of ‘pulling the guts’ (limit to one larva per farmer or 25-
30 larvae per FFS to avoid too much destructive sampling) to determine degree of DBM larval
parasitism by Diadegma in learning and adjoining crucifer fields, as follows:
5 Collect and record number of third and fourth instars DBM larvae collected;
5 Take one larva, hold on both ends between thumb and index finger, slowly pull, and
carefully observe Diadegma larva coming out a gut or bituka of DBM larva with aid of a
magnifying lens;
5 Count and record number of DBM larvae with Diadegma larval parasitoid inside;
5 Count and record number of DBM larvae without Diadegma larval parasitoid inside; and
5 Determine % parasitism following the formula below: