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

Section 4 • Integrated Insect and Rodent Pests Management
5 Collect NPV-infected cutworm larvae, characterized by their lesser leaf feeding
and inactivity, body softness and paleness, and non-sensitiveness to daytime heat
exposure.
5 Place collected intact dead larvae directly in a suitable plastic container. Leaves with
disintegrating dead larvae are collected and washed-off with water into container.
5 Record numbers of collected NPV-infected larvae in each container for proper
mixing ratio in NPV solution preparation.
5 Preserve NPV-infected larvae in plastic containers with cover inside a freezer,
if they will not be used immediately after collection. The infested larva can be
prepared as NPV solution before storage by dissolving 100 infested larvae in ¼ liter
of water. There will be approximately 4 infested larvae in a spoonful (10 mL) of
NPV solution.
(b) Mass-production of NPV-infected Cutworm Larvae
5 Select healthy third instars mass-reared cutworm larvae (larvae that molted three
times since they hatched from eggs).
5 Feed healthy cutworm larvae with taro, sweet potato, castor or mulberry leaves
soak in prepared NPV solution.
5 After two days, place NPV-infected larvae in fresh and untreated taro, sweet
potato, or mulberry leaves.
5 After another two days, place each NPV-infected larva in a plastic cup with fresh
and untreated taro, sweet potato, or mulberry leaves.
5 Collect NPV-infected larvae with apparent disease symptoms, place them in
plastic cups with cover, and store them in a freezer.
5 Collect dead larvae everyday and record number of NPV-infected larvae in each
container.
(c) Application of NPV Spray Solution Against Cutworm Larvae
5 In a 16-liter sprayer, put an equivalent of 10-15 NPV-infected larvae. Depending
on crop stage, 20-30 tank-load of water with NPV spray solution per hectare will
be needed.
5 Like conventional insecticides, spray NPV solution on crops that are infested by
cutworm larvae, in late afternoon. Since cutworm is nocturnal, spraying late in the
afternoon will ensure effectiveness of NPV spray solution against the pest.
5 Repeat spraying of NPV solution after 2 weeks if cutworm larvae infestation is
slight to moderate.
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