priciples of insecticide use in rice ipm

Insecticides in Rice IPM (DRR)
anaerobic conditions after the oxygen is depleted. The PH of the soil shows a tendency to reach the near
neutral, although may not exactly be neutral. The anaerobic bacteria and other microbes take the position
of aerobic bacteria and other organisms present under aerobically grown crops.
Under these conditions if insecticide or urea fertilizer is placed in the root zone of rice plants, these are
not subjected to oxidation which usually renders them to rapid degradation. Instead, these remain in the
same state for longer period. These chemicals are also near the root system, and hence are more easily
absorbed into the plant. The chemicals are not subjected to losses through volatilization, and leaching.
Therefore, several attempts were made to develop practical methods of placing the insecticides in the
root zone of rice plants. Pathak et. al. (1974) at IRRI took initiative in this line of work. Forty one
insecticides were evaluated under greenhouse conditions as granules, tablets or capsules placed at a
depth of 2.5 cm at a rate equivalent of 2 kg a.i./ha in the root zone of potted rice plants by using
Nephotettix virescens, Nilaparvata lugens and Chilo suppressalis as test insects. In their initial evaluation,
about 25 compounds were effective against N. virescens, while a lesser number exhibited good efficacy
against N. lugens and C. suppressalis. In further field trials, it was observed that a single application of
carbofuran, cartap or chlordimeform even at 0.5 kg a.i./ha controlled the insect pests equal to 3-4
applications of the same insecticides in the standing water.
Encouraged by these results, attempts were initiated at DRR (formerly AICRIP) where several insecticides
were tested by root-zone application method both in lead research and coordination (AICRIP 1977-80).
Similar attempts were also made in other countries like Indonesia (Shagir and Van, 1976), Korea (Choi et
al., 1977), India (Krishnaiah et. al, 1988b; Reddy and Krishnaiah, 1993) and China (Chiu et. al, 1980).
In the beginning, the insecticide granules were mixed in a suitable soil, and mud balls were prepared and
these mud-balls were placed in the root zone @ 1 for each hill or 1 for 2 or 4 hills. However, this method
was laborious, time consuming and many a situations uneconomical.
LIQUID INJECTORS FOR ROOT ZONE PLACEMENT
Liquid injector
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As an alternative, mixing the insecticides in water and injecting the emulsions
or solutions into the root zone was preferred. This necessitated the development
of machines to inject the liquid into the root zone. Many types of injecting
machines were developed and tested at IRRI. Reddy (1989) designed, developed
and tested a simple liquid injecting device for the purpose. This consisted of
attaching a lance with 4 delivery points suitable for injecting the liquid into a
depth of 2.5 cm in the root zone to the ordinary hand compression sprayer.
First the liquid is placed in the sprayer tank and held at suitable pressure. The
operator can carry the spray tank with modified attachment; place the injecting
points in the soil in such a way that it covers eight rows at a time. Then the
liquid is released for few seconds, which enable the insecticide solution/emulsion
to be placed in the root zone. The lance is lifted and placed for the next set of