and Integrated Pest Management - part - usaid

DEVELOPMflr r OF ACTION CONTROL TIRESHOLDS FOR MAJOR RICE PrM
aenescensMoore, the rice hairy caterpillar Rivula alimeta (Swinhoe), and th-; rice
caseworm Nymphula depunctalis(Guence). The rice monoculture ai. tdi stable
water supply favors their development. Farmers taught us to first scout for their
presence in the most flooded fields.
Pests present during the reproductive stage zr, leaffolders Cnaphalocrocis
inedinalis (Guence) and Marasmia patnalis (Bradley), the yellow rice borer
Scirpophaga incertulas (Walker), and the whitebacked planthopper Sogatella
furcifera (1-orvath).
Rice bug Leptocorisaoratorius(Fabricius), a pest of he ripening stage, is
more common in areas of thick vegetation like Cc.tabato.
Thresholds
Greater variability of yield loss was recorded between farms than sites,
indicating the need to adjust to prevailing insect abundance from field to field.
An ACT is composed of a character which has a life stage of the nest or a
symptom of damage. It has a unit value and is derived through sampling,
commonly sequential sampling, which is a time-saving method. Sampling is
followed by the use of an insecticide at a minimal dosage applied in a particular
way. All of the components of each ACT must work if it is to produce the
highest profit.
Farmers' Thresholds
Farmers monitor their fields for the occurrence of pests. Only a minority of
farmers apply insecticide by prophylactic scheduling. They carry out monitoring
concurrently with other farm operations like weeding, checking the water level
and clearing dikes. Farmers' ACTs are based on experience and are highly
qualitative. Farmers' ACTs are derived quickly, often from only what they see
while walking around their fields. They uap plants for hoppers and defoliators,
flush moths while walking along dikes, and observe changes in the size of
patches of damage over time. Farmers' ACTs, however, are as complex as those
developed by researchers.
ACTION CONTROL THRESHOLDS
Whorl Maggot
Adult flies are attracted to an open water surface to oviDoSit. They lay eggs
on newly transplanted seedlings 2-14 days after transplanting. Eggs hatch in 3­
5 days and the young maggots tunnel into the whorl of the rice plant. Damaged
unopened shoots are not completely severed so leaves emerge tattered in a
diagnostic way.
"Damaged leaves" were first used as the ACT character for this pest.
Experience showed this character to occur too late - 2 weeks after transplanting
- for effective con!rol. Very low percentage of control (26%) was obtained
from trials using "damaged leaves" (Table 2).
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